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November 2015 November 2015
Physics of Complexity @ ISC
The Institute of Complex System (ISC) of the National Research Council(CNR) was created in 2004.
The science of complexity studies the emergence of collective properties insystems with a large number of interacting elements. These elements mightbe atoms in a physical context or say macromolecules in a biological one, butalso individuals or companies in a socio-economic context.
Focusing on the structure of the interconnections and the general architectureof systems, the science of complexity departs from the traditional approachbased on individual components.
Rome, November 2015
ISC Units
Directorate and central administration
Via dei Taurini 19, 00185, Roma
SapienzaPiazzale Aldo Moro, 5, 00185 Roma
Tor VergataVia del Fosso del Cavaliere 100, 00133 Roma
MontelibrettiArea della Ricerca di Roma Montelibretti Via Salaria Km 29, 300 – Strada della Neve – 000100 Montelibretti, Roma
Sesto Fiorentino Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze
Luca Angelani
contacts
[email protected]: Fermi Building, 111http://glass.phys.uniroma1.it/angelani
keywords
● Active matter● Self-propelled particles● Modeling and simulations
Ensembles of animate organisms, such as motile E.coli bacteria, behave in a very rich and surprising way if compared to inanimate objects, such as atoms or molecules in aliquid. By converting chemical energy into mechanical motion, active suspensionsrepresent a very interesting class of out-of-equilibrium systems, giving rise to complexpattern formation and spatio-temporal behaviors.
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Active particles in confined geometry Swimmers dynamics is strongly influenced by boundaries.Self-propelled bacteria confined in micro-chambersconnected by thin channels spontaneously generate flowcurrents giving rise to self-sustained density oscillations.
Active Matter – Motile bacteria
Run-and-tumble dynamics Bacterial motion can be described as a simple run-and-tumblewalk, consisting in a straight line motion at constant speed (run)interrupted by a random reorientation of the swimming direction(tumble). The resulting dynamics (telegrapher's like equation ofmotion) can be analyzed in different contexts (external fields,escape problems).
Shaped and passive objects in bacterial bathsShaped objects or colloidal beads immersed in a bacterialbath experience “active” forces, giving rise to rectification phenomena and effective interactions. For example,asymmetrically shaped gears perform undirectionalrotational motion when immersed in a bath of self-propelled microorganisms.
X-rays scatering scatering to probe structure and dynamics of sof mater
Roberta Angelini
contacts
Office: Fermi Building, room 110
http://glass.phys.uniroma1.it/angelini
keywords● Soft Matter: experiments● Gel and glass transition● Structure and dynamics of disordered systems
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Sof mater systems exhibit complex behavior involving a
broad range of length and tme scales. For this reason,
alongside laboratory techniques such as DLS, rheometry and
DSC, synchrotron-based methods are powerful tools to extend
their study and understanding over such wide spatal and
temporal scales. This part of my work is developed mainly at
the European Synchrotron radiaton facility (ESRF) in Grenoble
through X-ray photon correlaton spectroscopy and small
angle X-ray scatering techniques and complemented with
neutron scatering measurements.[2] Nat. Commun. 5, 4049 (2014)
Fig.: Statc structure factor of a
colloidal clay, Laponite, across the
glass-glass transiton [2].
Gel and glass transiton in sof mater systems
Recent advances in the study of sof mater have led in the
last decades to a beter understanding of equilibrium and
non-equilibrium states and to the discovery of new phases
besides the ones commonly experienced in atomic or
molecular systems. In the wide panorama of sof materials,
an important role is played by colloidal suspensions that ofer
the possibility to observe unusual phase diagrams including
reentrant or empty liquid regimes [1], multple arrested
states, such as gels and glassy states and glass-glass
transitons [2]. My work is focused in partcular on charged
colloidal clays and more recently on colloidal microgels. The
experimental work is developed, in collaboraton with Dr. B.
Ruzicka, in our laboratories at Sapienza University, through
dynamic light scatering (DLS), diferental scanning
calorimetry (DSC) and rheometry and in collaboraton with
Dr. E. Zaccarelli for comparison with theory and simulatons.
[1] Nat. Mater. 10, 56 (2011).
F ig . : A r re s te d s t at e o f an
interpenetrated polymer network
colloidal microgel obtained by
increasing temperature.
Mario Alberto Annunziata
contacts
[email protected]: Dipartimento di Fisica, ed. Fermi, stanza 201Piazzale A. Moro, 2 00185 Roma (Italy)Tel.: +39 (0)6 49913489
keywords
● Granular materials● Soft matter● Econophysics
Granular materials and Softmatter
I work together with Dr. Alberto Petri andDr. Andrea Baldassarri on the subject:friction in granular matter.
We have developed a Molecular-Dynamicscode in order to simulate an assembly ofgrains under shear (see picture right).
Our approach follows the ones ofCundall&Strack., Massimo Pica Ciamarraet al., Silbert et al.
We are currently investigating themicroscopic and macroscopic properties ofgranular friction, together with a thoroughanalysis of the stick-slip motion whichtakes place.
I have also worked in the past on Softmatter subjects as mixtures of colloids andpolymers and ferrogels.
Econophysics
Since 2014 I have been working togetherwith Dr. Alberto Petri and Dr. GiorgioPontuale on the study of country-productmatrix exports.
We are investigating the type of thestatistical distributions which take place inthese flows and the properties of exportflows.
Tor Vergata unit
Ubaldo Bafile
contacts
[email protected]: Florence CNR Area, Building B, room 159
keywords
● Neutron spectroscopy
● Dynamical models of fluids
Microscopic static and dynamic structures in disordered systems
The microscopic structural and dynamical properties of fluids are a key topic instatistical mechanics of condensed-matter many-body systems, in the whole rangecomprising simple monatomic and molecular gases and liquids, non-simple liquids likehydrogen-bonded fluids, conducting fluids (liquid metals), semi quantum and quantumliquids. In these systems we have been investigating both single-particle and collectivephenomena.
From the experimental side, we apply neutron diffraction and neutron spectroscopytechniques. The accompanying non-trivial data analysis is conducted jointly with variouskinds of simulation methods.
The most important results of the last few years are:
- a theoretical analysis based on the reformulation of fit models, leading to the fullunderstanding of dispersion curves for collective excitations, and to a general exactrelation between decay times of memory functions and lifetimes of the spectral modes; - a theoretical analysis of time correlation functions of operators in many-body systems,proving their general property of being described as infinite series of exponential functionscorresponding to the eigenmodes of the frequency spectrum; - the development of optimized multidimensional Monte Carlo integration methods forevaluation of multiple scattering in inelastic scattering experiments; - the analysis of ab initio simulations in parallel with experimental data on liquid-metalmicrodynamics, leading to the determination of some types of unified features, shown to becommon to all classes of fluids, in contrast with the current point of view that involvesdifferent theoretical models; - the analysis of quantum simulation for liquid hydrogen, deuterium, and hydrogen isotopicmixtures, leading to the assessment of non-Gaussian behaviour in the single-moleculedynamics of quantum Boltzmann fluids.
Florence unit
Andrea Baldassarri
contacts
[email protected]: Fermi Building, 510https://aquilante.phys.uniroma1.it/~andreab
keywords
● Percolation● Granular materials● Stochastic processes
Rocky coast erosion and percolation theoryAs shown by a minimal numerical model,percolation theory can be used as a guide todecipher the physics of rocky coast erosionand could provide precise predictions to thestatistics of cliff collapses. I'm interested inpossible applications of percolation theory ingeomorphology, as revealed by irregulargeometries or anomalous statistics.
Friction is a very old, but still open field ofresearch, relevant from the physics at nano-scaleto earthquakes. The friction response of agranular material could be very fluctuating, due tothe anomalous stress propagation in the material.This systems represent an interesting laboratory,both experimentally and theoretically, for theintroduction of new models and concepts.
Irregular, bursty dynamics can be modeledvia simple stochastic processes, revealingunexpected connections between differentphysical systems (crackling noise).
Avalanche dynamics and crackling noise
Friction in granular materials
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Lara Benfatto
contacts
[email protected]: Marconi Building, room 110https://www.roma1.infn.it:~lbenfat
keywords
● Theory of Many-Body Systems● Superconductivity in low dimensions● Materials with Novel Electronic Properties
The inhomogeneous local DOS measured by STMshows an universal probability distribution of thelocal SC order parameter when properly rescaled
A typical example of competing states isprovided by strongly disorderedsuperconductors: here disorder tendsto order the charge, by localizing theelectrons, and pairing tends to order theglobal electronic phase, i.e. to form thes u p e r c o n d u c t i n g s t a t e . A s acompromise, the system develops anintrinsic inhomogeneous phase withunusual glassy properties.
G.Seibold et al. Phys.Rev.Lett.108, 207004 (2012).G. Lemarie et al. Phys. Rev. B 87, 184509 (2013).
In analogy with its counterpart in theStandard Model, in superconductors acollective Higgs boson emerges in thebroken-symmetry state. It is formed bycollective electronic excitations of theorder-parameter amplitude. However,such a bosonic collective modeinter feres dramat ica l ly wi th theunderlying fermionic quasiparticleexcitations, which control its dynamicalproperties and its coupling to externalprobes. This has crucial consequenceson its observability in equilibrium andout-of-equilibrium spectroscopy, a topicunder intense investigation in thecurrent literature.
The understanding of the electronic properties of complex solid-state systems,where one observes the competition between different phenomena, requires todevelop and implement a modern quantum-field theory approach. This includesseveral analytical techniques, ranging from a conventional perturbative expansion tothe derivation of the quantum functionals for the collective degrees of freedom
NbN disordered films
Schematicr e p r e s e n t a t i o n o fAmplitude (Higgs) andp h a s e ( G o l d s t o n e )m o d e s i nsuperconductors
T. Cea et al. Phys. Rev.Lett. 115, 157002 (2015).
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Emmanuele Cappelluti
contacts
[email protected]: Fermi Building, room 109, Ph.: 06-4991-3488http://pil.phys.uniroma1.it/~emmcapp
keywords
● Many-Body Interactions and Theoretical Physics in Condensed Matter● Superconductivity and collective phenomena● Graphene and low-dimensional systems
My research activity investigatesthe appearance of many-bodyphenomena o f fundamenta lphysics in a variety of specificcondensed matter systems.Examples of open research lineswhere Master theses are available:
Graphene and post-graphenecompoundsTheoretical modelling of electronic,lattice, thermodynamical, optical,and magnetic properties of two-dimensional materials (graphene,dichalcogenides,...).
Interactions and Pairing in Iron-based Superconductors andrecently discovered H
3S
Microscopical description of thescattering and pairing mechanismsin the normal state (transport,optical properties) and in thesuperconduct ing s ta te (gapsymmetry).
Lat t ice /spin polarons andInterplay between electron-lattice and magnetic interactionsMechanisms and properties ofcomplex objects (polarons) wheredifferent degrees of freedom(electron, lattice deformation, spin)are entangled at a local scale.Itinerant vs. trapped states.
Spontaneous broken-symmetryphases in layered compoundsNematic, charge and bond-density-waves driven by Hubbard-Hundinteract ions in layered two-dimensional materials.
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Silvia Capuani
contacts
Sapienza [email protected]: Fermi Building, room 319Laboratory: Segrè Building, room 5https://www.researchgate.net/profile/Silvia_Capuani
keywords
● Nuclear Magnetic Resonance Imaging● Anomalous diffusion in porous systems and biological tissues● Applied physics: Medical Physics and Cultural Heritage
Osteoporosis diagnosisby diffusion of water in cancellous bone and spectroscopic quantification ofbone marrow fatty acids.
S. Capuani, Microp.Mesop.Mater 2013;178:34S. Capuani et al. BioMed Res Intl 2015; 948610M. Rebuzzi et al. BONE 2013;57:155-163G. Manenti et al. BONE 2013;55:7-15
Micro MRI Fossil teeth, Root3D evaluation of bone regeneration
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Non Gaussian diffusion of water in porous material and human brain tissues
S. De Santis et al. MRM 2011;65(4):1043.S. Capuani et al. MRI 2013; 31:359-365
M. Palombo et al. JCP 2011;135,034504M. Palombo et al. Sci Rep 2013;3:2631
Claudio Castellano
contacts
[email protected]: Via dei Taurini 19, 4th floor, room 409http://sites.google.com/site/claudiocastellanohome/home
keywords
● Interdisciplinary applications of statistical physics● Complex networks● Dynamics of social systems
Statistical physics approach tosocial dynamicsIn recent years it has become widelyrecognized that many large-scale phenomenaobserved in soc ia l sys tems are the"macroscopic" emergent effect of the"microscopic" behavior of a large number ofinteracting agents. This has led to theintroduction of elementary models of socialbehavior (opinion dynamics, cultural andscientific evolution, language change). Many ofthese models are relatives of models that arestudied in modern statistical physics, and it isnatural to approach them using the sameconcepts and tools successfully applied inphysics.
C. Castellano et al., “Statistical physics of social dynamics”,Rev. Mod. Phys. 81, 591 (2009)
F. Colaiori et al., “A general three-state model with biasedpopulation replacement: analytical solution and application tolanguage dynamics”, Phys. Rev. E (to appear).
Spreading processes oncomplex networksDynamical processes have been studied fordecades on regular lattices and their behavioris generally well understood. When suchprocesses take place on a complex topology,what is the effect of the disordered interactionpattern on their phenomenology? In recentyears I have been in particular involved in theinvestigation of the behavior of spreadingprocesses, which range from infectiousdisease epidemics to “social contagion”, i.e.,
information diffusion or meme propagation.Complex networks topology has a very strongimpact on epidemic processes, facilitatingspreading and increasing the r isk ofpandemics. Nontrivial effects are responsiblefor this vulnerability and their understandingchallenges established theoretical approaches.
The study of epidemic-l ike spreadingprocesses in the social domain, spurred bythat the “big data” revolution is a very activeand promising field for future research.
C. Castellano and R. Pastor-Satorras, “Threshold for epidemicspreading in networks”, Phys. Rev. Lett. 105, 218701 (2010).
M. Boguna' et al., “Nature of the Epidemic Threshold for theSusceptible-Infected-Susceptible Dynamics in Networks”,Phys. Rev. Lett. 111, 068701 (2013).
R. Pastor-Satorras, C. Castellano, P. Van Mieghem and A.Vespignani, “Epidemic spreading in networks”, Rev. Mod.Phys. 87, 925 (2015).
Sapienza unit
Andrea Cavagna
contacts
[email protected],Office: ISC/CNR - Via dei Taurini 19 – Floor 4th
http://www.sapienza.isc.cnr.it/component/content/article/68.html
keywords
● Collective Behavior in Biological Systems● (Non-Equilibrium) Statistical Mechanics● Inference, Modeling & Simulations
Collective Behavior in BiologicalSystemsThe basis of our overall methodology islinking the experimental data (observedbehaviour) with the theories explaining theinteractions rules governing large animalgroups. This broad mandate requires aninterdisciplinary approach ranging fromfield experiments, to computer vision, tostatistical physics. In general, we havesplit our focus in two areas: i)experimental data gathering andprocessing; ii) data analysis and theory.Our experimental work is carried out in thenatural habitat of the animal we arestudying. We use multiple synchronizedhigh speed cameras to capture imagesequences of the aggregation. By usingnovel computer vision algorithm, we arethen able to reconstruct the 3D trajectoriesof each individual in the group. Our dataanalysis follows a theoretical approachinspired by the principles of statisticalphysics.
Many-body physics in real timeI am working on devising new methods todetect a growing static correlation length indeeply supercooled liquids. By usingamorphuos boundary conditions wemeasured for the first time athermodynamic correlation length. In sodoing we test the validity of differenttheoretical frameworks of the glasstransition, namely the Adam-Gibbs theoryand the Mosaic (aka Random First Order)theory. We are also trying to measure thesurface tension between differentamorphous phases in deeply supercooledliquids and to establish a link betweenstatic relaxation and dynamicheterogeneities through the concept ofsurface tension. Check my pedagogicalreviews on spin-glasses and supercooledliquids, Spin-Glass Theory for Pedestrians[J. Stat. Mech. (2005) P05012] andSupercooled Liquids for Pedestrians,Physics Reports 476, (2009), P51
figure
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Fabio Cecconi
contacts
[email protected]: Via dei Taurini, 19 tel:06-4993.7452 http://denali.phys.uniroma1.it/~cecconif/
keywords
● Transport of biopolymers in nanopores● Statistical mechanics of complex systems● Nonlinear Physics and Chaos
Transport of proteinsNanopore technology is the “art” of retrievingchemical and physical information aboutbiomolecules through their transport behavioracross nanopores (nanoscale “holes”) FigB.This field is considered the new frontier ofsingle-molecule manipulation and sequencingwith relevant applications to biology andmedicine. Experiments are becoming veryaccurate and produce a countless number offacts and data which the theory is called toexplain. Main theoretical tools: Stochastic Processes,Model l ing and Simulations, StatisticalMechanics.
Statistical mechanics of complexsystemsUnderstanding complex phenomena like theemergence of collective or auto-organizeddynamics in many-body systems requires tomaster advanced concepts and methods ofstatistical mechanics and stochastic processtheory. Particular important is the modeling ofcomplex systems which f inds severa lapplications e.g. to biology, material science,economic or social phenomena. We areinterested to study complex behaviors ingranular materials and transport processes.
Nonlinear Physics and ChaosNonlinearity is a general element of naturalphenomena and Chaos theory is thesystematic study of the “unexpected” effectsproduced by nonlinearities. In particular, twoinitial conditions differing for an infinitesimalerror, which according to Newton's physicswould yield similar results, can led to vastlydifferent outcomes (Butterfly effect). Thediscovery that unpredictable behaviors areconsistent with deterministic laws changed theway we perceive the world around us. Non-linear physics is the interdisciplinary field thatdevelops mathematical tools and concepts toclassify and characterize: chaotic behaviors, strange attractors and the related fractal structures.
Fig. Transport of a protein by a pulling force
Fig. A strange attractor showing a fractalstructure.
Fig. Chain of nonlinearoscillators considered aparadigm of a complexsystem.
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Milva Celli
contacts
[email protected]: building B, room 133 phone +39 055 5226633http://www.fi.isc.cnr.it/people/userprofile/milvacelli.html
keywords
● Raman and neutron spectroscopy, neutron diffraction● Confined hydrogen in nanostructured geometries ● Structure and dynamics in simple and quantum liquids● Neutron instrumentation
Raman and inelastic neutronscattering on hydrogen clathratehydrates Clathrate hydrates are solid inclusioncompounds, where water moleculesconstitute a regular lattice, characterizedby the presence of polyhedral nano-cages,inside which guest molecules of a differentcompound are confined. The dynamics ofthe trapped molecules are well describedin terms of localized excitations.Considerable effort has been devoted inrecent years to the study of hydrogenclathrate hydrates, because of theirpotential as efficient and environmentallyfriendly materials for hydrogen storage. Inaddintion to this pratical importance,h y d r o g e n c l a t h r a t e s a r e a l s o o fconsiderable theoretical interest asprototypical examples of confined quantumparticles.
M. Celli et al., J. Chem. Phys. 139, 164507(2013)D. Colognesi, J. Chem. Phys. 141, 134501 (2014)
Non-Gaussian self-dynamics ofliquid hydrogenUnderstanding the single-particle, or self-dynamics of liquids is a longstandingresearch theme in condensed matterphysics. One of the most importantapproaches to this problem is based on theso-called Gaussian approximation (GA), inwhich it is assumed that the motion ofparticles is only determined by the timeautocorrelation function of the particlevelocity (vaf). Although often adopted, thevalidity of GA is not yet well assessed indifferent wave vector ranges, especially forquantum Boltzmann liquids (i.e. H2, D2,Ne..). By mean of neutron spectroscopyinvestigation and quantum simulation westudy the limits of the GA in the selfdynamics of quantum liquids and wedeterminate the first non-Gaussiancorrection term.
M. Celli et al. Phys. Rev. B 84, 140510(R), (2011)D. Colognesi et al., Chem. Phys. 446, 57 (2015)
Florence unit
Massimo Cencini
contacts
[email protected]: CNR, Via dei Taurini 19, IV floor room 412http://denali.phys.uniroma1.it/~cencini
keywords
● Turbulence and transport of fields and particles in turbulent flows● Chaos and dynamical systems● Population dynamics
Transport of swimming micro-organisms in turbulenceSubstances transported by a turbulent flowtypically mix quickly (e.g stirring milk intocoffee). What does happen to micro-organisms transported by a turbulent flow?They are typically very small and have thesame density of the fluid so that are expectedto follow the fluid elements and thus to mixvery efficiently. However, if they can swim, asbacteria or some species of algae, somethingcounterintuitive can happen:they can unmixforming fractal clusters. This phenomenonhas been studied experimentally, in a vorticalflow, and numerically, in a turbulent flow, forgyrotactic microalgae.
W. M. Durham, E. Climent, M. Barry, F. De Lillo, G. Boffetta,M. Cencini, R. Stocker Nature Comm. 4, 2148 (2013)
F. De Lillo, M. Cencini, W. M. Durham, M. Barry, R. Stocker,E. Climent, G. Boffetta, Phys. Rev. Lett. 112, 044502 (2014)
M. Cencini, M Franchino, F Santamaria, G. Boffetta, preprint
arXiv:1511.01255 (2015)
Neutral biodiversity models Species abundance distributions and how thenumber of species changes with the area(Species Area Relationships) can becaptured by simple neutral models, with a flat“fitness” landscape. Efficient algorithms havebeen developed to study nontrivial regimes ofsmall speciation rate and large local populationsizes, relevant to microorganisms ecology. Wefound that large local populations give rise to shallower SAR, in accord with field observations.
figure
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In the case of fast mutating viruses (e.g., Influenza virus), the virus-host interaction is driven by cross-immunity: after being infected by a strain, the host acquires immunity to a set of other strainsantigenically similar to the infecting one (i.e., triggering the same host immune response). The evolutionary dynamics of viruses is then ruled by their relative antigenic distance. Can we understand the nontrivial relation between antigenic and genetic distance?
Francesca Colaiori
contacts
[email protected]: Fermi Building, 510it.linkedin.com/in/FrancescaColaiori
keywords
● Network Science● Quantitative Linguistics● Biophysics
In all languages, rules have exceptions in the form of irregularities.Since rules make a language efficient, the persistence ofirregularity is an anomaly. How do language systems become rulegoverned? How and why do they sustain exceptions to rules? Frequent words are unlikely to change over time (e.g., frequentverbs tend to maintain an irregular past tense form). What is therole of frequency in maintaining exceptions to rules?C
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Interdisciplinary researchPhysics as a tool
Social networks have empirically been found to be assortative (i.e.,the degrees of neighboring nodes are positively correlated), whileother networks (e.g., technological, biological) show the oppositepattern (disassortative). Why is that so? How do these patterns change in signed networks, where relationsindicate trust/distrust, friendship/enmity? Do individuals who dislikemany others tend to dislike each other, or do they dislike those whodislike only very few others?
Tools from statistical physics, modeling, analytical approach (whenever possible),simulations, data analysis, web-based experiments.
typical problems
methods
Dynamics of Virus-Host interaction
Rules and Exceptions in Language Dynamics
Structure of Social Networks
Sapienza unit
Daniele Colognesi
contacts
Office: building B, room 133, phone: +39-055-5226681
http://www.fi.isc.cnr.it/people/userprofile/dankolog.html
keywords
●Inelastic Neutron Scattering●Hydrogen and Hydrogen-containing Materials●Dynamics of Quantum and Semi-quantum Fluids●Neutron Scattering Instrumentation
Inelastic Neutron Scattering ona Composite of NaAlH4 and
Nanoporous Carbon
Inelastic neutron scattering spectra of amelt-infiltrated composite of NaAlH4 and
active carbon fibers have been studied atlow temperature for two sampleconditions: as prepared and subjected tohydrogen desorption-absorption cycling.After a careful data analysis, theexperimental results have been comparedto the corresponding spectroscopic datataken from bulk NaAlH4 and Na3AlH6.
Evident signatures induced by infiltrationprocess onto the NaAlH4 phonon bands
have been detected, showing up as astrong peak broadening and smoothingtogether with, in some cases, an energyshift. Traces of Na3AlH6, appearing as an
extra intensity between 130 and 200meV, seem also confirmed. Further work,both experimental and based on ab initiosimulations, is surely needed in order torationalize the finding of the presentmeasurements.D. Colognesi et al., J. Phys. Chem. A 115, 7503 (2011).D. Colognesi et al., J. Phys. Chem. A117, 7314 (2013).
Non-Gaussian effects in the selfdynamics of semi-quantum fluids
An extension of the non-Gaussian correctionto quantum fluids is devised, with a particularinterest in the so-called semi-quantumliquids. In this case a detailed correctionscheme for both the short- and the long-timebehaviors of the intermediate scatteringfunction is proposed. Subsequently, apractical test of this approach is performedon neutron scattering spectra derived fromliquid para-H2 and para-H2 plus normal D2
mixtures. These experimental findingsconfirm the validity of our approach andshow that a description of the self dynamicsbeyond the Gaussian approximation isnecessary even in simple liquids affected bymild quantum effects.D. Colognesi et al., Chem. Phys. 446, 57(2015).
Florence unit
Claudio Conti
contacts
[email protected]: Fermi Building, 108http://www.complexlight.org
keywords
● Photonics and nonlinear optics, experiments and theory● High performance computing● Theoretical physics
The enlightened game of life
Is complexity linked with light? We decide ifsomething is complex or not by observing itss t ruc tu re and hence i n te rac t i ng w i t helectromagnetic waves. Is this fact morefundamental than that? We want to developtheoretical models for assessing the linkbetween light and complexity, starting from thesimplest one: the Conway's Game of Life
Complexity arises when there is disorder andnonlinearity. Photonics is full of examples in whichhighly nonlinear regimes occur in the presence ofdisorder. The case of light-matter interaction inrandom systems is specifically important for anovel class of devices named random lasers. Inour laboratory we study random lasers in bio-templated materials and other complex systems.
Highly nonlinear regimes in optics are formallyidentically to quantum gravity enhancedquantum mechanics, including a generalizeduncertainty principle. Can we simulate quantumgravity in the lab?
Quantum gravity simulation
Random lasers, experimental activity
Sapienza unit
Francesco Cordero
Office: 06 4993 4114
http://www.artov.isc.cnr.it/your-
details/userprofile/francesco_cordero.html
dynamics of point defects and domain walls, phase transitions ferroelectric, magnetic, superconducting, ion conducting perovskites dynamic elastic properties of solids
Phase diagrams of ferroelectric
perovskitesThe dynamic elastic properties of ferroelectric
(FE) perovskites are studied in close
collaboration with Floriana Craciun for the
dielectric properties.
PbZr1-xTixO3 (PZT) has been studying for 60
years and is the most used piezo-electric
material, but the newly measured elastic
compliance, with anomalies in correspondence
of all the structural transitions, entails a
revision of the phase diagram, e.g. with new tilt
instabilities of the ZrO6 octahedra and splitting
of the polar and tilt modes at the
antiferroelectric transition. These new features
are under study by other techniques through
international collaborations.
The need to obtain materials with properties
similar to PZT or improved but without the toxic
Pb has boosted the study of the mechanisms
enhancing the piezo-electric activity of PZT
and similar materials at the morphotropic
phase boundary (MPB) between FE rhombo-
hedral and tetragonal phases. A maximum in
the compliance in correspondence with the
MPB of PZT and the Pb-free materials NBT-BT
and BCT-BZT has been shown to be due to
the intrinsic ability of the polari-zation to easily
rotate, rather than only an extrinsic effect from
domain wall motion.
F: Cordero et al. Phys. Rev. Lett. 98, 255701 (2007).
F: Cordero et al. Phys. Rev. B 81, 144124 (2010).
F: Cordero et al. Appl. Phys. Lett. 103, 122903 (2014).
Defects, ion conduction and
polaronsThe anelastic spectra vs T at different
frequencies allow the relaxation, hopping and
reorientation frequencies of point and
extended defects and polarons to be
measured.
In particular, O vacancies are difficult to study
with other techniques, though they heavily
affect the materials properties as unwanted
defects, ionic charge carriers or dopants. Our
studies are focused on H and O vacancies in
SrTiO3, ferroelectric, super-and ion conducting
perovskites.
We also study the metal-insulator and
magnetic transitions involving Jahn-Teller
distortions in manganites and nichelates.
F: Cordero, Phys. Rev. B 76, 172106 (2007).
F: Cordero et al. Phys. Rev. B 82, 104102 (2010).
F: Cordero et al. Phys. Rev. B 84, 125127 (2011).
PZT phasediagram fromanelastic anddielectricspectra
octahedral tilting in theperovskite structure
Tor Vergata unit
contacts
keywords
Floriana Rusanescu
Craciun
Office: 06 4993 4024
The dielectric properties of these materials are studied
in close collaboration with Francesco Cordero for the
anelastic properties. Recent results allowed to refine
the phase diagram of La-doped PbZr0.9Ti0.1O3,
interesting for electro-optical applications, high energy
density capacitors, digital displacement transducers
etc., near the phase boundary between competing
antiferroelectric and ferroelectric phases.
F. Craciun et al., J. Appl. Phys. 117, 184103 (2015).
Multiferroicity of ferroelectric perovskites doped with magnetic impurities
Multiferroic materials that exhibit simultaneously
magnetic and ferroelectric (FE) order are
investigated due to their potential applications in
multifunctional sensors, spintronics, data storage,
etc. We found emergent magnetic properties in
(Sm,Fe)-doped PbTiO3
FE perovskite and an
abnormal behavior of dielectric constant and loss
below the temperature where the magnetization
also increases. HRTEM evidenced a polar
nanostructure, besides normal FE domains.F. Craciun et al., Appl. Phys. Lett. 102, 242903 (2013).
F. Craciun et al., J. Appl. Phys. 116, 074101 (2014).
Nano/macro domain transitions in nanostructured polar materials
We have investigated thermally driven and electrically driven nano/macro domain
transformations in different nanostructured polar materials like NBT-BT and PLZT.
Such transformation has been evidenced also in epitaxial PLZT thin films under
anisotropic strain. F. Craciun et al., Appl. Phys. Lett. 102, 162902 (2013).
F. Craciun et al., J. Appl. Phys. 112, 124106 (2012); N. Scarisoreanu et al., J. Appl. Phys. 116, 074106 (2014);
F. Craciun, Phys. Rev. B 81, 184111 (2010).
● Phase transitions● Nanostructured polar materials● Multiferroic materials
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Matthieu Cristelli
contacts
[email protected]: Fermi Building, room 206http://matthieu-cristelli.strikingly.com
keywords
● Economic Complexity● Finance● Agent-Based Modeling & Self-Organization of Markets
The heterogeneous dynamics ofEconomic Complexity: what will be theg r o w t h o f t h e G D P a n d t h ecompetitiveness of China, the USA,Vietnam and Sierra Leone in the next 10years? The answer is ‘it depends’:predicting the evolution of fitness andincome is strongly dependent on theregime a country occupies. There existeconomic regimes for which the fitness(a synthetic measure of the countrycompetitiveness) is able to effectivelyuncover the hidden potential of growth ofcountries. Forecasting country growthfaces hurdles which are similar thosefound in predicting dynamical systems(i.e., the atmosphere, climate, wind andocean dynamics). On this account thereis strong evidence for a high degree ofheterogeneity in the growth dynamics ofcountries. We observe the emergence ofdifferent regimes of economic complexityand in particular there are severalregimes for the patterns of evolution of
Economy can be portrayed as a complex adaptive process and competitivenesscannot be seen anymore as the final result of equilibrium systems where feedbacksare linear and uncoupled. The present data-centric era, methods from complexityand dynamical systems provide a unique opportunity to lead the scientific shift of theeconomic thinking and ground it empirically.
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countries in the fitness-income plane, asillustrated in the figure Depending onthe position in the fitness-income plane,we are able to distinguish two mainregimes: a laminar-like regime in whichthe fitness appears to be predictive, orat least informative, of country growth;and a chaotic regime in which thef i tness is poor ly or comple te lyuncorrelated with the evolution of thewealth of those countries.
Tacchella et al. Scientific Reports 2, 723 (2012).Cristelli et al. PloS ONE 10(2):e0117174 (2015).
Marco D’Alessandro
contacts
Office: Artov, room 0B16
Tel: +39 4993 4310
keywords
Statistical mechanics and Monte Carlo methods
Optical microscopy and spectroscopy
Instrument development for space
Development of scientificinstrument for space-typeapplications
Development and realizaton of a shuter
for neutral atoms for the ELENA
instrument, as part of the ESA mission
"BepiColombo“.
Hyperspectral confocal microscopy
Theoretcal analysis of light interacton
with mult layered systems in confocal
microscopy
Monte Carlo solution of theinverse problems in classicalstatistical mechanics
Analysis of the “inverse-problem”for classical statistical systems,both in the continuum and on thelattice. I have developed aprocedure, based on theapplication of the MaximumEntropy Principle, for thedetermination of the microscopicinteraction potential starting fromthe knowledge of a set ofcorrelation functions.
M. D’Alessandro and F. Cilloco,Physical Review E 82, 021128(2010) [arXiv:1006.3656]M. D’Alessandro, Physical ReviewE 84, 041130 (2011)[arXiv:1206.4811v1].
figure
Reconstructon of the interacton potental of
a model of liquid Aluminum at high density
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Antonio Di Trolio
contacts
Office: 2B11, Tor Vergata
keywords
● Doping, defects and ferromagnetism in oxide-based materials
● Laser growth and processing of thin films and nanostructures
● Dilute magnetic oxides
Dilute Magnetic Oxides exhibit roomtemperature ferromagnetism whose originis still unclear in most cases. I n Z n
1-xCo
xO the occurrence of
ferromagnetism can be associated to theconcurrent presence of defects formed byoxygen vacancies close to Co atoms (Co-Vo complexes) and charge carriers. Aqualitative picture explains the long-rangeferromagnetic coupling of the Co atomsinvolved in the Co-Vo complexes. We also investigate the effects ofhydrogen irradiation on ferromagnetismand carriers of Zn
1-xCo
xO samples .
Effect of Co doping on conductivity andferromagnetism in Zn
1-xCo
xO thin films.
Ref. J. Mater. Chem. C 3, 10188 (2015)
● Pulsed Laser Deposition ofthin films and nanocomposites
The growth of thin fi lms ofnanocomposite materials by pulsed laserdeposition indicated a route to synthesizemetallic nanocrystals with well-definedposition in a semiconducting matrix. By proper selecting process parametersand materials it is possible to assemble ondemand composite multifunctional materials at the nanoscale for reliable magneto-optical and plasmonic applications.
Ref. J. Phys. Chem. C 117, 687, (2013)
Planar arrays ofCo nanocrystalsin polycrystallineTiO
2 .
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Luisa Ferrari
contacts
Office: 0B016
keywords
●Hyperspectral Imaging●Electronic properties of surfaces and interfaces ●ARPES from self-assembled systems of reduced dimensionality
Confocal MicroSpectroscopy on
biological systems in vitro and in
vivo
The applicaton of the hyperspectral
confocal refectance microscope led to the
defniton of a non-invasive and label-free
method for discriminaton of cells in co-
culture. It is currently directed to the
study of living cells and tssues with the
aim of looking for the correlaton between
optcal data and the formaton of
carcinomas and specifc genetc defects of
the skin.
Maps of the dichroic signal for two enantomers of
chiral molecules, acquired by angular resolved
photoemission with circularly polarized light
Ferrari L. e al. Phys.Rev. B 91, 085408 (2015)
Physics of low-dimensional materials
The study of the electronic propertes of
nanostructured systems with diferent
geometry is of fundamental importance for
the development of new nanostructured
functonal materials. We are interested in
exploring : the efects of fnite size and
interface on the electronic and magnetc
propertes of ultra-thin flms and
multlayers; the high resoluton (energy and
momentum) electronic structure of
magnetc and non-magnetc material with
large spin-orbit interacton; graphene
grown on metal substrates; self-organized
chiral molecules on surfaces.
Melanocyte
cell image
and its
spatally
resolved
refectvity
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Stefano Focardi
Office: room B163
● Roe deer● Distance sampling
Movement ecology Movement ecology is an emerging
ecological discipline whose aim is studying
animals’ movement in relation to their
internal state, to the presence of
conspecifics, competitors and predators
and to the ecosystems complexity. The
partecipation to the EURODEER working
group allows to develop researches on
movement of roe deer (Capreolus
capreolus) thorough Europe with specific
reference to migration, natal and
reproductive dispersal and interspecific
competitions
Pupulation assessmentEffective monitoring of wildlife population is
a basic need for cost-effective
management and conservation. An
effective method for population assessment
is represented by nocturnal distance
sampling, where animals are detected by
night using thermal imaging. To be
effectively implemented we develop a
number of experiments under natural
conditions in protected areas.
Levy flights In the last 8 years a passionate debate
about the presence of Lévy movements in
wild animals has developed. To move
forward it is necessary to develop new
insight in searching behavior under field
conditions, making use of the most
innovative tracking device such as GPS
tags. In particular we investigate the
foraging behavior of shearwaters a bird
species able to perform foraging
excursions very far from their breeding
colonies.
Photo: Jacopo
Cecere
Photo Barbara
Franzetti
Population dynamics Populations dynamics of wildlife is
fundamental for our understanding of the
dynamics of environments. The main target
of this study is represented by the wild boar
(Sus scrofa) and by its impacts on and
relationships with natural and agricoltural
ecosystem.
Photo: Federico
Morimando
● Capture-mark-recapture● Mathematical, statistical modelling
Florence unit
contacts
keywords
● Levy flights●Wild boar
Andrea Gabrielli
contacts
[email protected]: Fermi Building, office 111http://pil.phys.uniroma1.infn.it/~andrea
keywords
● Stochastic processes and networks for interdisciplinary applications● Networks and complex structures in brain science● Long range interacting systems
Economic complexity: If we study how different countries produce different products, we find data which look in contrast with standard economic theories: differentiation of production appears much more important than specialization for advanced economies. Studying the network structure of world productionthrough a non-linear pagerank-like approach permits to uncover the hidden potential of growth of countries and to classify the technological complexity of products.
Complex structures in brain and NMRHuman brain is one of the most complex object of studyin science and it is characterized by a spatio-temporal multiscale and multilevel structures. Nuclear Magnetic Resonance is the best in vivo tool to study both its 3-d disordered structure and its complex behavior.With this experimental technique, supported by the generalized diffusion theory, we can study thediffusion of water molecules in each cell (i.e. voxel)of a 3-d grid to get 3-d brain mages (DNMR). The same technique is used to analyze the temporal coordination between different regions of thebrain during its functioning (fMRI). Network theory then permits to determine thetopological properties of this functional network and characterize in the best way thefunctional connectivity and coordinated behavior of different brain regions.
Quasi-stationary states in long range interacting systemsParticle systems with long range interactions (e.g. self-gravitating gas) present a peculiarbehavior which differs strongly from standard short range interacting systems both atequilibrium (e.g. ensemble inequivalence, negative specific heat) and far from it. Inparticular their out of equilibrium dynamics is characterized by the presence of quasi-stationary states in which the system gets trapped. They are due to the prevalence ofcollective motion on the two-body collision dynamics which in general drives the system atequilibrium. Its study is still an open issue.
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Silvia Gentilini
contacts
[email protected]: Fermi Building, room 114http://complexlight.org/
keywords
● Random photonics● Shock waves in complex systems ● Optomechanics
Shock WavesThe dispersive shock waves (DSWs) are anonlinear phenomenon, where the dispersionregular izes the occurrence of abruptdiscontinuities by means fast coherentoscillations. Because their coherent nature,DSWs represent a suited candidate toexperimentally investigate the competitionbetween disorder and nonlinearity in complexmaterials [1].
The DSWs have also provided the physicalfirst realization of the inverted quantumoscillators. Such systems that were theorizedby Glauber to explain the link between thereversible microscopic and irreversiblemacroscopic scale, represent nowadays anovel perspective to exploit shock-waves inuseful applications as lasers, optical amplifiersand X-ray generation [2].[1] N.Ghofraniha et al, PRL 109, 243902 (2012).[2] S.Gentilini et al, Sci. Rep. 5, 15816 (2015).
The study of the propagation of light in complex nonlinear systems allows toobserve a plethora of phenomena generated by the interplay between disorder andnonlinearity. Understanding such interplay furnishes insights of the fundamentalmechanisms ruling the light transport regimes as well as opens the road to newapplications in the field of the light-driven device.
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Optomechanics
The concept of radiation pressure is based onthe exchange of momentum between photonsand matter. In recent theoretical studies anonlinear opto-mechanical response ispredicted and we experimentally measurethermal and electronic nonlinear effects. Bymeans of an atomic force microscope (AFM) we are able to detect the nanometric deflectionof cantilevers due to optical forces exerted bya continuous wave laser beam [3].
We also theoretically consider the effect oflight scattering on the opto-mechanical forces,finding that light trapping mechanismsenhance their action [4]. All these findings feed the exploitation of lightfor controlling motion of complex dielectricstructures and realize light-activated devices
[3] C.Ciancico, Master degree thesis (2015).
[4] S.Gentilini et al., PRA 91, 043813 (2015).
D e t a i l o f t h eexperimental setup to measure the radiation pressure on AFM
cantilevers [3].
Giovanni Giacomelli
contacts
Mail: [email protected]: +39 055 522 6655Web:www.fi.isc.cnr.it/people/userprofile/giovanni_giacomelli.html
keywords
● Semiconductor laser physics● Dynamical systems ● Stochastic processes
Dynamical systems with long delayed feedbackThe correspondence between long-delayed systemsand one-dimensional spatially-extended media enablesa direct interpretation of purely temporal phenomena interms of spatio-temporal patterns. On the basis of thisresult, we provide the evidence of a characteristicspatio-temporal dynamics -coarsening- in a long-delayed bistable system. Nucleation, propagation andannihilation of fronts, leading eventually to a singlephase, are observed in an experiment based on a laser with opto-electronic feedback.
Charactering the response of chaotic systems
figure
A class of systems with multiple, hierarchically long timedelays uncover features otherwise hidden in theirtemporal dynamics using a suitable space-timerepresentation. The behaviour in the case of two delaysis shown to ''encode'' two-dimensional spiral defects anddefects turbulence
We characterize the response of a chaotic system byinvestigating ensembles of, rather than single,t ra jec to r ies . T ime-per iod ic s t imu la t ions a reexperimentally and numerically investigated. Thisapproach allows detecting and characterizing a broadclass of coherent phenomena that go beyondgeneralized and phase synchronization. In particular, wefind that a large average response is not necessarilyrelated to the presence of standard forms ofsynchronization.
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Emilia Giorgetti
contacts
[email protected]: Building B, Room 119Present affiliation: Ministry of Foreign AffairsItalian Embassy in Mexico City
keywords
● Plasmonics● Nanomaterials● Laser ablation
Plasmonic nanomaterials forspectroscopic applications
Preparation and characterization ofnanoparticles of coinage metals withtunable plasmonic properties (related to size and/or aspherical shape).
These nanoparticles cause SurfaceEnhanced Raman response (SERS) ofmolecular adsorbates and, underappropriate experimental conditions,also metal enhanced fluorescence(MEF).
Beyond enhanced spectroscopy, theycan find application in novel sensingdevices and in theragnostic (i.e. earlydetection and/or photothermal therapyof tumors).
Laser ablationLaser ablation is a green physicalapproach to the production ofnanomaterials. A pulsed laser beam isfocused onto a target immersed in aliquid. The material extracted by laser-target interaction can aggregate intonanoparticles. This method permits toobtain stable metal colloids also in puresolvents, such as water. Under properexperimental conditions it can be usedto prepare oxide and/or metal oxide orbimetallic nanoparticles. Thenanoparticles can be unprotected, butalso coated by different molecularadsorbates, when required.Among the wide range of applications,Ag colloids are interesting for theirfungicide and bactericide properties,while Au or iron opxide colloids can find important applications in drug deliverysystems and Pd colloids in catalysis.
figure
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A u
A g
A u
A g
A u
A g
Ag
Pd
Ag
Pd
Andrea Gnoli
contacts
[email protected]: Fermi Building, 012http://www.sapienza.isc.cnr.it/your-details/userprofile/andrea_gnoli.html
keywords
● Granular Materials● Brownian Motors
Granular Materials
Granular materials are studied andused to test various fascinatingtheories in the field of nonequilibrium statistical physics.
Many different experiments havebeen realized in the GranularDynamics Laboratory in the FermiBuilding, ground floor, Room 012.In our experiments grains aremade of steel or plastic beads ofvarious size, in the 1 – 4 mmrange. The beads are kept inmovement by a shaker and variousdifferent regimes are realized(granular gas and liquid) in variousdifferent setups (3d, 2d and also1d). The dynamic of the grains isstudied by high speed camerasand/or probed by intruders.
Brownian Motors
Brownian motors are a class ofdevices that extract useful workfrom noise. Such an extraction,which is impossible in the classicalequilibrium thermodynamicframework, is made possiblethrough the use of granulars thatare, by definition, in nonequilibrium conditions. Therectification of fluctuations ischallenging from the experimentalpoint of view and the final directionof motion is not easily predictedwithout a suitable theoreticalmodel.
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Neda Ghofraniha
contacts
[email protected]: Fermi Building, room 114https://www.complexlight.com
keywords
● Random photonics● Nonlinear waves● Nonlinear optical properties of soft matter
Organic RLs:1) We realized lasing devices from paper f lexible sheets by creating on the cellulose f ibers micro- f luidic porous channels in which a f luorescent dye can f low by capillarity. We show how the emission properties depend crucially on the width, shape and curvature of the microchannels as well as on their functionalization with colloidal additives. 2) We observed tunable RL emission from scattering nano-aggregates of a thiophene oligomer, obtained in a controlled way by soft lithographic techniques. The emission from this organic dye in compact solid state showed the experimental evidence of Replica Simmetry Breaking.
I. Viola et al. J. Mater. Chem. C 1, 8128 (2013)N. Ghofraniha et al. Opt. Lett. 38, 5043 (2013)N. Ghofraniha et al. Laser Photon. Rev. 7, 432 (2013)N. Ghofraniha et al. Nat. Comm. 6, 6058 (2015)
Bio-templated RLs:We observe single mode lasing emission from bio-mimetic materials. The transformations of the complete hierarchical structure of paper f ibers into inorganic materials allow to obtain very eff icient RLs with sub-nanometer lasing modes. We show that the distribution and the intensity of the modes change in different points of the system depending on the local structure of the material, in this way the RL emission can be used as a f ingerprint of porous materials with high potentiality for example in medical diagnostics and cultural heritage. Moreover we demonstrate that resonant modes are extended in space, they interact and compete for the available energy. We plan experiments with other bio-inspired materials as diatoms, chitin f ibers and graphene quantum dots.
Random Laser (RL) consists of a random assembly of scattering structures dispersed into an optical gain medium in which the optical cavity is merely represented by multiple scattering processes of light. In the last 20 years the research in RLs has provided important insights into some aspects of fundamental physics as Anderson localization and Bose-Einstein condensation and opened new routes towards the fabrication of innovative photonic devices.
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Thomas Kreuz
contacts
[email protected]: Via Madonna del Piano 10, room B130http://www.fi.isc.cnr.it/users/thomas.kreuz/
keywords
● Computational neuroscience● Data analysis● Measures of spike train synchrony
Measures of spike train synchrony
In both experimental and computationalneuroscience there is an increasingdemand for algorithms capable ofanalyzing large amounts of spike traindata. One of the most crucial tasks is theidentification of similarity patterns with avery high temporal resolution and acrossdifferent spatial scales. In recent years wehave developed three time-resolved andparameter-free measures of spike trainsynchrony: The ISI-distance, the SPIKE-distance, and SPIKE-synchronization. In asecond step we apply these measures toreal neuronal data (medial temporal lobe ofepilepsy patients, monkey retina, auditorysystem of songbirds etc.) kindly providedby collaborating laboratories.
SPIKY – Graphical user interface
SPIKY is a Matlab-based graphical userinterface which facilitates the application ofour time-resolved measures of spike trainsynchrony to both simulated and real data.SPIKY includes implementations of the ISI-distance, the SPIKE-distance and SPIKE-synchronization all of which have beenoptimized with respect to computationspeed and memory demand. SPIKY alsocomprises a spike train generator and anevent detector which makes it capable ofanalyzing continuous data. Finally, SPIKYincludes programs aimed at the analysis oflarge numbers of datasets and theestimation of significance levels. SPIKY iscomplemented by the open source Pythonlibrary PySpike hosted on github.
Florence unit
Rosanna Larciprete
contacts
Office: 0C05
keywords
●Properties of surfaces, interfaces and ultrathin films●Graphene and 2D materials●Surface reactions
Structural, electronic, andchemical properties of surfacesand interfaces.Most of the chemical and physicalprocesses involving solid materials takeplace at the surface. These aspects becomeeven more important for nanomaterialssince the reduced dimensions make thesurface rather than the bulk to dominate the physicochemical behavior. Therefore theknowledge of the interplay between thestructural, electronic and chemicalproperties of the material surfaces is thekey to optimize processes such as layergrowth, interface formation, thin filmsynthesis, gas-solid interactions, catalysis,corrosion, oxidative reactions and gassensing. We combine electronic, optical andmicroscopic diagnostics to investigate theintrinsic properties and the surface reactionst r i g g e r e d b y e x t e r n a l a g e n t s i nnanostructured materials, organic/inorganici n t e r f a c e s , u l t r a t h i n f i l m s a n dheterostrucures.
Decomposition of TIPS-Pentacene on Au(111)monitored by fast XPS of the C1s core level.Ref. J. Phys. Chem C 18, 22522 (2014)
Growth and functionalization of2D materials. Due to its outstanding electronic, optical,morphological and mechanical propertiesgraphene has opened up new horizons forthe research and development of two-dimensional (2D) materials. These arematerials that do not need to besupported by a substrate to exist andtherefore can be isolated as free-standing one atom thick layers, and that due toconfinement of electrons and to the lackof strong interlayer interactions usuallyexhibit optical and electronic propertiesdifferent from their analogous 3Dsystems. Our research focuses on thedevelopment of methods to synthesizegraphene and other 2D materials, todefine their stability and understand howtheir properties are modified by dopingand functionalization or by the formationof interfaces with dissimilar materials.
Graphene functionalized with O containingspecies. Rif. JACS 133, 17315 (2011)
Tor Vergata unit
Stefano Lepri
contacts
[email protected]: room 120 tel +39 055 5226620www.fi.isc.cnr.it/users/stefano.lepri
keywords
● Non-linear dynamics and chaos ● Out-of-equilibrium processes in physics● Fluctuations and random processes
Anomalous heat conduction Physical phenomena in reduced spatialdimension (D<3) are often qualitativelydifferent from their three-dimensionalcounterparts. An important example thathas been thorughly studied by our group isthe anomalous heat conduction in chainsof coupled oscillators. Numerical andanalytical studies showed that correlationsare so relevant to lead to a divergingthermal conductivity. This implies abreakdown of the usual hydrodynamicapproach based on phenomenologicalconstitutive equations (the Fourier law inthis context). These idea found recentlyapplications in the framewok of nanoscaleheat transfer and has been testedexperimentally for quasi 1D and 2Dsystems like carbon nanotubes andgraphene.
Asymmetric nonlinear wavetransmissionNonlinearity can lead to nonreciprocaltransmission l : the same wave istransmit ted di f ferent ly in opposi tedirections. Different regimes of scatteringcan exist such as nonreciprocal modulationvia Hopf bifurcations of the steadysolutions and a regime of a "chaotic diode",where transmission is regular in onedirection and chaotic in the opposite one.
Diffusion on Levy structuresThe effect of quenched, long-rangecorrelated, disorder on anomalousdiffusion has been studied. The powerfulideas of scaling has been employed topredict the transmission in engineeredoptical materials called “Levy glasses”.
Florence unit
José Lorenzana
contacts
[email protected]: Marconi Building, 112http://www.sapienza.isc.cnr.it/component/content/article/112.html
keywords
● Theory of Many-Body Systems● Superconductivity● Emerging materials
Complex SolidsMy main interest are complex solidsintended as materials in which differentphases compete producing interestingcollective behavior. Competition arisebecause interactions and the kineticenergy contribute similarly to the energy,therefore complex solids are nor in theweak nor in the strong coupling regimewhich makes them difficult to treat withconventional perturbative approaches.Competition between phases often leads togigantic responses to externalperturbations which makes complex solidsinteresting for applications. I use many-body numerical and analytical techniquesto model the behavior of system withfascinating properties as high temperaturesuperconductors and multiferroics(materials which have ferroelectric andmagnetic order coupled). My work is oftenclose to concrete experiments performedby partner groups and in the last yearshave been focused on time-dependentphenomena as collective modes ofsuperconductors (including the possibilityto observe the analogous of the Higgsboson in condensed matter), generation ofmagnetic responses with an electric pulseor vice versa and understand the physicsof many-body quantum systems out ofequilibrium.
Many-body physics in real timeIn the last years dramatic technicalprogress have enable experiments wherequantum matter is perturbed and itsevolution is monitored in the femtosecondtime scale. The figure shows experimentsby our partners at Laussane [Mansart et al.PNAS, 110, 4539 (2013)] where thereflectivity as a function of energy ismonitored as a function of time delay afteran impulsive perturbation. Ultrafast timeresolution allows to see lattice vibrations(A and D) and also electronic oscillations(B and E). The material is a hightemperature superconductor and theelectronic oscillations are attributed to thesuperconducting condensate. Modelingthese and related experiments can help tounderstand the mechanism ofsuperconductivity in these materials, one ofthe main open problems in physics.
figure
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Stefano Luccioli
contacts
[email protected]: building B, room 126 phone +39 055 5226626
keywords
● Computational neuroscience● Nonlinear dynamics and chaos ● Out-of-equilibrium processes
Functional Hubs Neurons
Recent experiments have shownthat perturbations at the singleneuron level can impact the overallsynchronous dynamics of neuralcircuits. We study, by usingrealistic models, the emergence ofself-organized pools of a fewneurons (cliques), responsible for
the triggering of the synchronousactivity of the network. Theseneurons are hubs in a functional
sense, as the played role is notrelated to the intrinsic degree ofconnectivity but to the sequentialand coordinated order of spikeemiss i on p reced ing t hes y n c h r o n o u s e v e n t . T h eperturbation of even one singleneuron of the clique can bring to
the arrest of the co l lec t ivesynchronous act iv i ty o f thenetwork.
S.Luccioli et al PLOS Comp.Biol. 2014
Florence unit
Architecture of the clique
Sequential activation of Hubs Neurons
● Plasmonics● Metal Nanoparticles● Plasmonic sensors
Surface plasmon resonance kinetics of therecognition by specific antibodies of potassiumpumps hosted in bilayer lipid membranes
Giancarlo Margheri
contacts
[email protected] n.119, Building B at Area di Ricerca CNR diSesto Fiorentino
keywords
Plasmonics is a field of Optics that dealswith the interaction of optical beams withthe free electrons of noble metalsproducing collective motions known as“surface plasmons”(SPs). The light-SPsi n t e r a c t i o n c a n p r o v i d e a h i g hintensification of light intensity at themetals interfaces, that become actuallyideal sensitive tools to be exploited inseveral applications. The confined fieldscan be induced by a guided interfacepropagation or by dipolar or multipolar localresonances in nanostructures. In bothcases, the phenomena are referred as“surface plasmonic resonances”. As theconditions for the resonant excitation ofSPs strongly depend on the refractiveindex of the metal surroundings, thissuggested a powerful way to developsensitive physical-chemical, label-freesensors. This dependence has beenexploited also in other fields, like non linearoptics, or in the ultra-sensitive SurfaceRaman Enhanced (SERS), where thesignals can be intensified up to severalorders of magnitude with respect to theconventional Raman analysis.. Plasmoniclocalization is also an efficient tool toenhance the fluorescence emission (MetalEnhanced Fluorescence, MEF) or to excitethe Multi Photon Luminescence (MPL)emission by metal nanoparticles.
Florence unit
C e l l u p t a k e o f N I R - a b s o r b i n g g o l dnanoparticles (white dots) emitting via MPL.Inset: triangles side ~50 nm
Massimo Materassi
contacts
[email protected]: building B, room 127 phone +39 055 5226627http://www.fi.isc.cnr.it/people/userprofile/maxmat.html
keywords
● Dissipative systems, metriplectic algebræ ● Near-Earth Plasma and Space Weather● Mathematical Ecology
Metriplectic systems Metriplectic formalism is a framework toturn dynamical systems with dissipationinto algebræ of Leibniz brackets. Inparticular, when complete systems aredealt with, their entropy plays the role ofgenerator of the dissipative irreversiblecomponent of motion. Many dissipativesystems have been “algebrized” in thisway: in particular, my contributions are onplasmas and fluids. Developments areexpected in Quantum Mechanics.
● M Materassi, E Tassi, Physica D 241 (6), 729-734 (2012).
● M Materassi, Entropy 17 (3), 1329-1346 (2015).
Near-Earth Plasma and SpaceWeatherMy oldest line of research is ionosphericdynamics, from the point of view ofdynamical system theory. Participating toprojects on Space Weather, I am studyingthe near-Earth plasma as a complexsystem forced and structured by the Sun'sactivity and the geomagnetic field. In thisinvestigation there is room for multi-scales t a t i s t i c s o f G P S s i g n a l s , M H Dreformulation via stochastic and fractalmethods, and the use of information theorytools to detect causal relationships.
● A.W. Wernik, L. Alfonsi, M. Materassi, RadioScience 42 (1) (2007).
● M. Materassi, G. Consolini, Physical reviewletters 99 (17), 175002 (2007).
● M. Materassi, L. Ciraolo, G. Consolini, N.Smith, Advances in Space Research 47 (5),877-885 (2011).
● M. Materassi, G. Consolini Journal of PlasmaPhysics 81 (06), 495810602 (2015).
Florence unit
Mathematical ecology Ecological webs are represented andstudied through the population dynamics ofthe species composing them. My researchis focused at the moment on scavengingand kleptoprasitism among big mammals,and competition among species of algæ.
Fulvio Mazzocchicontacts
[email protected], Ed. 5. PT St. 2http://www.isc.cnr.it/staff-members/fulvio-mazzocchi/
keywords
● Epistemology ● Philosophy of Complexity ● Knowledge Organization
Epistemology andPhilosophy of Complexity
I am involved in investigatingcomplexity theory from aphilosophical point of view. In particular, I am concernedwith the epistemology ofcomplexity. My research also focuses onanalyzing complexity as a newpossible paradigm, especiallywith respect to thereductionism - holism debate
(e.g., in the biological field).
Knowledge Organization
Knowledge organization dealsbasically with the issue ofordering knowledge.My main interests are thephilosophical and theoreticalfoundations of knowledgeorganization. I have also participated inmany projects concerning theconstruction and developmentof Knowledge OrganizationSystems (KOS), such as
thesauri.
figure
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Mauro Missori
contacts
[email protected]: Fermi Building, S03http://www.isc.cnr.it/staff-members/mauro-missori/
keywords
● Cultural heritage: degradation of ancient paper ● Ultraviolet-visible-infrared and THz spectroscopy● Optical and structural properties of inhomogeneous systems
Optical degradation of ancientpaper at the nanoscale
Yellowing of ancient paper is responsible forsevere degradation of ancient artifacts. Thestudy of this phenomena is complicated by thefact that paper sheets are inhomogeneoussystems whose optical properties are stronglygoverned by light scattering effects. It isnecessary to apply suitable experimentalapproaches and specific models for lightpropagation in turbid media in order to recoverthe optical spectra of compounds responsiblefor yellowing. Comparison with theoreticalcondensed matter computational simulationsallows to describe and quantify at thenanoscale the modification of celluloseresponsible for ancient paper visualdegradation. This approach has been appliedto the famous Leonardo Da Vinci's self-portrait[1]. New research activities are now on goingto detect the degradation rate of this master-piece and on other famous drawings ofLeonardo. Research activities are carried on incollaboration with the Physics Departments ofthe University of Rome “Sapienza” and TorVergata, with the Chemistry Department of theUniversity of Krakow, Poland, and with theItalian Minister for Cultural Heritage.
[1] A. Mosca Conte, O. Pulci, M.C. Misiti, J. Lojewska, L.Teodonio, C. Violante, and M Missori “Visualdegradation in Leonardo da Vinci's iconic self-portrait: Ananoscale study”, Applied Physics Letters 104, 22,224101 (2014)
Biological systems
Ultraviolet-visible-infrared and THzspectroscopy allow to study the optical andstructural properties of non-homogenoussystems formed by biological fibers andbiomaterials of medical interest and theirinteraction with water. Research work is alsofocused to the understanding of degradationphenomena of these materials caused bydifferent aging factors (environmental,chemical, endogenous). Information recoveredattracted the attention of companies and led toan ongoing collaboration.
Montelibretti unit
Marco Montuori
contacts
[email protected]: Fermi Building, 510http://www.sapienza.isc.cnr.it/statistical-dynamics/statistical-cosmology.html
keywords
● Globular Clusters dynamics● Galaxy interactions
Globular Clusters (GCs) are old starclusters in the galaxy and cornerstonefor our understanding of the formation,structure and dynamics of Milky Way.Last decade has seen the discovery oftidal tails emanating of GC.Tails are anew probe of the potential of the galaxyand its time evolution. Throughnumerical simulation and observationalcomparison we can explore thefeatures of dark halo and its dynamics
Galaxies are recognized as the product ofevolution lasting nearly 14 billion years. Itis clear that many galaxies interact withneighboring ones and galaxy interactionsare believed to be the key evolutionarymechanism, in particular for the early-type.We are studying models and numericalsimulations to understand which are thedominant physical processes which drivestheir evolution and produce the richnesswe observe in the universe
Galaxy interactions
Globular Cluster dynamics
Sapienza unit
PCA applied to Raman
mapping for the rational
design of functional
nanostructuresPrincipal Component Analysis (PCA)
can be applied to Raman mapping as a
very robust method for a rapid and
trusty classification of samples, which is
fundamental to improve the design of
functional nanostructures and to
optimize the preparation procedure for
the specific application. Such an
approach has been recently applied to
analyse the Raman maps collected on
carbon nanotubes at different degree of
oxidation and functionalization with
various dye labeling molecules (results
on Rhodamine shown on the left).
Valentina Mussi
Office: Rome, Tor Vergata Area, Via Fosso del
Cavaliere, 100 Rooms 0C05, 2B14
Tel. +390649934166
www.tech4bio.eu
● Vibrational Spectroscopy and Imaging● Nanotechnology applied to Biomedicine● Biosensors
Tech4BioThe inter-Institutes initiative Tech4Bio,
collecting many researchers of CNR in Rome,
is to promote the intersection between different
disciplines, to provide a valuable opportunity to
exchange information and expertise, to create
connections and collaborations among
researchers and to build a bridge between
companies and places traditionally dedicated to
frontier research. The group deals with
biosensors and biochemistry, microscopy and
spectroscopy, development of advanced
microfluidic devices and lab-on-chips for
Bioanalytics and Diagnostics, characterization
at the micro and nano-scale, design and study
of novel smart biomaterials.
figure
Tor Vergata unit
contacts
keywords
Simona Olmi
Email: [email protected]: 126, Building Bhttp://www.fi.isc.cnr.it/people/userprofile/simona_olmi.html
● Neural Networks● Phase Oscillators● Out of Equilibrium Statistical
Mechanics
Dynamics of Massively Connected andSparse Neural Networks
We have investigated the role played by the topology inpromoting coherent activity in excitatory diluted pulse-coupled neural networks at a microscopic andmacroscopic level. In particular, we considered a dilutedrandom network where neurons were connected as in adirected Erdös-Renyi graph with average connectivityscaling sublinearly with the number of neurons in thenetwork. In these “massively connected” networks wehave shown that in the thermodynamic limit the dynamicsof coherent collective states coincide with that of fullycoupled networks. However, the random dilution of theconnections induces inhomogeneities in the neuronalbehaviors for any finite system size, promoting a weakform of chaos, which vanishes in the limit of infinite size. Inthis limit, the disordered systems exhibit regular (nonchaotic) dynamics thus recovering the properties of ahomogeneous fully connected network. The situation isquite different for a “sparse network” characterized by aconstant connectivity, independent on the size of thenetwork. In fact, on one side we found that a few tens ofrandom connections are suffcient to sustain a nontrivialcollective dynamics. In other words, collective motion is arather generic and robust property and does not require anextremely high connectivity to be sustained. On an otherside, the collective motion coexists with a microscopicallychaotic dynamics that does not vanish in thethermodynamic limit and turns out to be extensive (thenumber of unstable directions is proportional to thenetwork size). More specifically, various classes ofdynamical models on random sparse networks have beenstudied and in all cases, irrespective of the presence of themacroscopic phase, we found that the chaotic dynamics is always extensive. Extensive chaos has been alreadyfound in spatially extended system with nearest-neighbourcoupling (diffusive coupling) induced by the additivity ofthe system. In our case this property is highly nontrivial, asthe network dynamics is non additive and it cannot beapproximated as the juxtaposition of almost independentsub-structures.S. Olmi et al., Physical Review E 81, 046119 (2010).L. Tattini et al., Chaos 22, 023133 (2012).S. Luccioli et al., Phys. Rev. Lett. 109, 138103 (2012).S. Olmi and A. Torcini, Scholarpedia 8 (10), 30928 (2013).
Hysteretic transitions and chaotic chimerastates in networks of Kuramoto oscillatorswith inertiaWe performed finite size numerical investigations andmean field analysis of a Kuramoto model with inertia forfully coupled and diluted systems. In particular, weexamined, for a Gaussian distribution of thefrequencies, the transition from incoherence tocoherence for increasingly large system size and inertia.For sufficiently large inertia the transition is hystereticand within the hysteretic region clusters of lockedoscillators of various sizes and different levels ofsynchronization coexist. A modification of the mean fieldtheory developed by Tanaka, Lichtenberg, and Oishi[Physica D, 100 (1997)] allows to derive thesynchronization profile associated to each of theseclusters. By increasing the inertia the transitionbecomes more complex, and the synchronizationoccurs via the emergence of clusters of whirlingoscillators. The presence of these groups of coherentlydrifting oscillators induces oscillations in the orderparameter. We have shown that the transition remainshysteretic even for randomly diluted networks up to alevel of connectivity corresponding to few links peroscillator. Finally an extension to a system of twosymmetrically coupled networks of Kuramoto oscillatorswith inertia is analyzed. In this system the existence andthe dynamical properties of novel chaotic chimera statesare investigated, concentrating both on the microscopicdynamics and the macroscopic behavior.S. Olmi et al., Phys. Rev. E 90 (4), 16 (2014).
figure
Florence unitcontacts
keywords
Antonio Scala
contacts
[email protected]: Fermi Building, 104https://sites.google.com/site/antonioscalaphys/
keywords
● Complex Networks: Critical Infrastructures, Social Networks● Statistical Mechanics: Energy Landscapes, Soft Matter● Computational Physics: Hard body simulations, Monte Carlo
Complex Networks and Power Grids
Electric power-systems are one ofthe most important criticalinfrastructures. We apply statisticalmechanics to understand emergingphenomena in power grids
Self Healing Networks
We study self-healing models ofcomplex networks modelling.Obvious applications are toinfrastructural networks like gas,power, water, oil distribution.
Social Networks
We focus on data-drivencomputational models of complexsocio-cognitive systems: spread ofinformation and opinions, socialhuman behavior, evolution ofsocial networks. We aim todevelop innovative mathematicalmodels and computational tools tobetter understand, anticipate andcontrol massive social phenomenawith a complex systems approach.
publications
● Abruptness of Cascade Failures in Power GridsScientific Reports 4, 3694
● Self-Healing Networks: Redundancy andStructureDOI: 10.1371/journal.pone.0087986
● Opinion dynamics on interacting networks:media competition and social influenceScientific Reports 4, 4938
Sapienza unit
Oriele Palumbo
contacts
[email protected]:Physics Dpt, Marconi Building, room 360http://www.sapienza.isc.cnr.it/your-details/userprofile/oriel.html
keywords
● Spectroscopies● Innovative materials for energy storage● Phase transitions
Materials for hydrogen storage
The most promising way to store hydrogen isthe solid state storage, but at present a lot offundamental research is still needed to makesuch solid state tanks satisfactorily compatiblewith the targets of current applications.Best candidates are metal hydrides andcomplex hydrides. A big role in increasingtheir capacity and enhancing the hydriding anddehydriding kinetics is played by the artificialmanipulation, like nanostructuring of thepowders, their mechanical alloying andcatalysing. We study the hydrogenation anddehydrogenation fundamental mechanisms ofsuch novel materials by means of mechanicaland infrared spectroscopies, thermal analysisand ab initio simulation.
A. Paolone, F. Teocoli, S. Sanna. O. Palumbo and T. Autrey,J. Phys. Chem. C 117 129-134 (2013).
A. Paolone, F. Vico, F. Teocoli, S. Sanna. O. Palumbo, R.Cantelli, D.A. Knight, J. Trepovich and R. Zidan,J. Phys. Chem. C 116 16365-16370 (2012).
A. Paolone, O. Palumbo, P. Rispoli, R. Cantelli, T. Autrey, A.Karkamkar, J. Phys. Chem. C Lett. 113 10319-10321 (2009).
Hydrides as new anodes forlithium batteries
The incorporation of lithium by hydridesthrough an electrochemical conversionreaction is a promising alternative to Liintercalation into graphite for next-generationLi-ion cells.This reaction has been proved only for acouple of metal hydrides. We are currentlystudying the applicability of complex hydridesand possible improvements of the hydridesperformances in the cells by means of artificialnanostructuring.
D. Meggiolaro, G. Gigli, A. Paolone, F. Vitucci, S. Brutti,J. Phys. Chem. C 117 22467-22477 (2013).
Sapienza unit
Annalisa Paolone
contacts
[email protected]:Physics Dpt, Marconi Building, room 360http://www.sapienza.isc.cnr.it/your-details/userprofile/paolone.html
keywords
● Spectroscopies● Innovative materials for energy storage● Phase transitions
Ionic liquids and theirinteractions with membranes
Ionic liquids (ILs), which are inorganic saltswith melting point below 100°C areenvironmentally friendly solvents with usefulproperties. Moreover their attractive propertiescan be tuned by variation of the cation andanion. Our research is focused to achieve abetter physical understanding of the ionsinteractions and dynamics within the liquids bymeans of infrared and mechanicalspectroscopies, thermal analysis and ab initiosimulation.The occurrence of phase transitions and theirkinetics is studied too. In particular, it is showed that in the compositesystems usually used for applications, theinteraction with the swelling membranemodifies the physical properties of ILs.
F. M. Vitucci, D. Manzo, M. A. Navarra, O. Palumbo, F.Trequattrini, S. Panero, P.Bruni, F. Croce, A. Paolone,J. Phys. Chem. C 118 5749-5755 (2014).
F. M. Vitucci, F. Trequattrini,O. Palumbo, J.-B. Brubach,P.Roy, A. Paolone, J. Phys. Chem. A 118 8758-8764 (20014).
F. M. Vitucci, O. Palumbo, F. Trequattrini,J.-B. Brubach, P.Roy, F. Croce, A. Paolone, J. Phys. Chem. C under review.
figure
New materials for lithiumbatteries
We investigate the fundamental properties ofnew materials considered as promising as highenergy density electrodes for lithium batteries,such as LiNi
0.5Mn
1.5O
4 (LNMO) or LiCoPO
4
(LCPO). We studied the disorder of LNMO bymeans of EXAFS, the vacancy dynamics inLNMO by anelastic spectroscopy and theinfrared phonon spectrum of LCPO.
G. Greco, S. Brutti, F. M. Vitucci, L. Lombardo, M. Koentje, A.Savoini, A. Paolone, S. Panero, J. Phys. Chem. Cdoi:10.1021./jp5063622.
F. M. Vitucci, O. Palumbo, A. Paolone, R. Cantelli, S. Brutti,S. Panero, J. Alloys Compds. 604 83-86 (2014).
S. Brutti, J. Manzi, D. Di Lecce, F. Vitucci, A. Paolone, F.Trequattrini, S. Panero, Mat. Lett. under review.
Sapienza unit
Alberto Petri
contacts
[email protected]: Fermi Building, 109http://old.isc.cnr.it/ita/staff/petri/
keywords
● Dynamics of granular matter● Disordered materials● Complexity in society, biology and economics
Topic 1In our world, granular matter is moreubiquitous than crystals, however itsdynamics is much less understood. Grainsalso provide a laboratory model forearthquakes and dissipative processes. Wetry to improve our understanding of thecollective dynamics of grains performinglaboratory experiments and numericalsimulations, and try to describe it bymeans of stochastic processes.
Topic 2Structural phenomena occurring indisordered materials often bring thefeatures of criticality, i.e. long rangecorrelations and self similar patterns, likefor example in the pattern of a propagating
Topic 3Understanding the dynamicsunderlying human and biologicalactivities is difficult. However thenow available large amount of dataprovides lot of information. We arepresently investigating the mutualimport-export relations of world-widecountries, pointing out analogieswith some ecological systems.
crack. Despite their complexity, it isoften possible to understand anddescribe these phenomena bymeans of simple models like cellularautomata and lattice gas.
Sapienza unit
Laura Pilozzi
contacts
[email protected]: Via dei Taurini 19, 4th floor, room 409 http://www.isc.cnr.it/staff-members/laura-pilozzi/
keywords
● Exciton-polaritons● Photonic-crystals● Microcavities
Microcavity polaritons The composite boson nature of excitonsplays a key role in their many-bodyphysics. The undistinguishability of the twocarriers leads to different exchangeprocesses that enter ex-ex interactions andare a source of nonlinearity in the opticalproperties of semiconductors. A compositboson formalism is then necessary to studyp o l a r i t o n - p o l a r i t o n s c a t t e r i n g i nsemiconductor microcavities.L. Pilozzi et al. Phys. Rev. B 82, 075327 (2010)M.M.Glazov et al. Phys. Rev. B 80, 155306 (2009)
Subwavelenght gratingsArtificial electromagnetic media, achievedby structuring on the subwavelength scale,are an important tool in modern optics toe n h a n c e d e v i c e p e r f o r m a n c e b yengineering the electromagnetic space andcontrolling waves propagation. Structuredsurfaces, as free standing dielectricgratings, can be designed to act as mirrorssince they show scalable energy bands ofhigh reflectivity, polarization sensitive. Placed in a cavity volumethey allow the tailoring ofthe electric field intensity and the enhancementof light-matter interaction.
L. Pilozzi et al. Phys. Rev. B 86, 045301 (2012)
Resonant photonic crystals Are sequences of sites with resonantexcitations long range coupled through anelectromagnetic field. They can form wideenergy band gaps, as in periodic photoniccrystals, and localized states as indisordered media. Fibonacci and Thue-Morse chainsdemonstrate scaling invariance and self-similarity for exciton-polariton dispersion.(Fig.1). Bichromatic structures with compoundnon-centrosymmetric unit cells, followingthe off-diagonal Harper model, showtopological properties as the existence ofprotected edge states.
A. N. Poddubny, et al. Phys. Rev. B 80, 115314 (2009)A. V. Poshakinskiy, et al. Phys. Rev. Lett. 112, 107403(2014)
figure
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Sapienza unit
Maria Gloria Pini
contacts
[email protected]: phone +39 055 5226628, room 128, building BHome page address:http://www.fi.isc.cnr.it/people/userprofile/mgpini.html
keywords
● Magnetism in low-dimensional systems● Molecular magnetic chains● Ultrathin magnetic films
Dynamic control of magneticnanowires by light-induceddomain-wall kickoffs (a) The time evolution of the paradigmaticIsing magnetic molecular nanowireCo(hfac)2NITPhOMe is normally described
by Glauber dynamics, consisting indomain-wall nucleation (with energy cost2J, where J~75 K is the intrachainexchange constant) and subsequentpropagation via a random-walk process (atno energy cost). The resulting relaxationtime of the magnetization follows anArrhenius law, τ=τ0exp(2J/T), where the
spin-flip attempt rate is τ0 ≈ 4x10-11s.
(b) By continuous irradiation of the sampleby a HeNe laser (λ=632.8nm) at low power(≈1μW/cm2), a much faster decay of themagnetization, τexc=τ0,excexp(2Jexc/T)>>τ,
is obtained. This is realized through akickoff mechanism. The adsorption of aphoton at one site of the chain creates aFrenkel exciton. For the exciton duration,τ0,exc≈10-8s>>τ0, the intrachain exchange
coupling with a spin at the exciton site(green arrow) becomes Jexc ≈50K<J.
The above mechanism is perfectlyreversible, proving that Glauber'sstochastic dynamics of the Ising model canbe easily controlled using light with powernearly 1000 times smaller than in previousoptical switching methods.
Rotatable magnetic anisotropy inFeGa films with stripe domainsIn magnetoelastic films of FeGa, thespontaneous formation of an up/down stripedomain structure is induced (for filmthickness greater than a critical valuetc≈40nm) by the competition between the
easy-plane magnetic dipolar interaction anda moderate perpendicular magneticanisotropy. Using Brillouin light scattering tostudy the spin-wave excitations in a 65nmFe0.8Ga0.2 film (PRB 89, 024411), we have
shown that the stripe pattern is associatedwith a nonzero “rotatable” magneticanisotropy (effective field Hrot ≈ 1kOe), sonamed because the stripes orientation inthe film plane is determined only by thesample history (direction of the lastsaturating field).
Florence unit
Paolo Politi
contacts
ISC-CNR, via Madonna del Piano 10, Sesto F.no (FI)Office: B128 (Tel. 055 522 6686)[email protected]://sites.google.com/site/ppoliti/
keywords
● Nonequilibrium statistical physics● Nonlinear dynamics● Pattern formation
Dynamics and energetics in far from equilibrium systems
A physical system which is relaxing towards equilibrium and a system driven far fromequilibrium may display some common features: the instability of an homogeneous state,the rising of a new structured state and the adjustement of its typical length scale. These phenomena can be observed in biophysics, condensed matter, atomic physics,granular materials, and so on. Relevant questions are: What are the dynamics of thesystem? Do they depend on energetic factors? Is the system able to attain the groundstate and on what time scale?
For example, in some cases dynamics can be frozen. This is the case for the biologicalmembrane depicted in the figure below and confined between walls, where the membraneadheres to both walls. The resulting structure of adhesion patches is ordered or disordereddepending on wall permability and it is frozen because the energy of the membranedepends on its curvature (via bending rigidity) rather than by its total length (throughsurface tension). If surface tension or fluctuations are substantial, they may trigger acoarsening process where the size of adhesion patches increase in time.
The figure illustrates the main ingredients: the adhesion potential (left) and the effect ofbending rigidity, which induces oscillations in the patches attached to the walls.
In collaboration with Thomas Le Goff and Olivier Pierre-Louis (Lyon).
Florence unit
Marco Pretti
contacts
[email protected] (Dipartimento di Scienza Applicata e Tecnologia)Politecnico di Torino
keywords
● Complex fluids● Statistical inference and combinatorial optimization● Random graphs
Thermodynamic anomalies ofwater
Water is an ubiquitous substance,which nonetheless exhibits animpressive amount of anomalousproperties, among which the wellknown density maximum at 4°C atatmospheric pressure. Simplestatistical-mechanical models canqualitatively describe suchanomalies, and may helpinvestigate the conjecturedconnections with supercooled andglassy states of water.
Random graph theory
The cavity method is an advancedmean-field technique, generallyused to study disordered systems.This method can also be employedto investigate some issues inrandom graph theory, for instancethe emergence of extensiveregular subgraphs.
Belief Propagation
A lot of statistical-inferenceproblems of high technologicalimportance (for instance: error-correction for digital transmissionover a noisy channel) can beformalized in terms of calculationof a Boltzmann distribution forIsing- or Potts-like models definedon heterogeneous graphs. BeliefPropagation is a very efficientalgorithm to perform suchcalculations, based on a statistical-mechanical method of the meanfield type (Bethe-Peierlsapproximation).
Graphical model of a genericstatistical-inference problem
Sapienza unit
Gian Piero Puccioni
contacts
[email protected]:Room B-135 - ISC, Via Madonna del Piano,10 Office: 50019, Sesto Fiorentino (FI)Ph:+39 055 5226682
keywords
● Nonlinear Optics● Numerical Simulations● Lasers
Stochastic Simulator formodeling the transition to lasingWith G.L.Lippi
A Stochastic Simulator (SS) is proposed,based on a semiclassical description of theradiation-matter interaction, to obtain anefficient description of the lasing transition fordevices ranging from the nanolaser to thetraditional "macroscopic" laser. Steady-statepredictions obtained with the SS agree bothwith more traditional laser modeling and withthe description of phase transitions in small-sized systems, and provide additionalinformation on fluctuations. Dynamicalinformation can easily be obtained, with goodcomputing time efficiency, which convincingly
highlights the role of fluctuations at threshold.
Slow dynamics in semi-conductor multi-longitudinal-mode laser transients governedby a master modeWith G.L.Lippi
We examine the response to the suddenswitch of the pump parameter in a multimodesemiconductor laser with intensity coupling ona model whose validity has been successfullycompared to experimental results. We find theexistence of a very slow modal evolutiongoverned by a master mode, which reaches itssteady state on a time scale that is a couple oforders of magnitude longer than that of thetotal intensity.
Fast dynamics and spectralproperties of a multilongitudinal-mode semiconductor laser:evolution of an ensemble ofdriven, globally couplednonlinear modes.With G.L.Lippi
We analyze the fast transient dynamics ofa multi-longitudinal mode semiconductorlaser on the basis of a model with intensitycoupling. The dynamics, coupled to theconstraints of the system and the below-threshold initial conditions, imposes afaster growth of the side modes in theinitial stages of the transient, therebyleading the laser through a sequence ofstates where the modal intensitydistribution dramatically differs from theasymptotic one. A detailed analysis of thebelow-threshold, deterministic dynamicalevolution allows us to explain the modaldynamics in the strongly coupled regimewhere the total intensity peak andrelaxation oscillations take place, thusproviding an explanation for the modaldynamics observed in the slow, hiddenevolution towards the asymptotic state
Florence unit
Andrea Puglisi
contacts
[email protected]: Fermi Building, 406http://denali.phys.uniroma1.it/~puglisi/welcome.html
keywords
● Granular materials● Out-of-equilibrium statistical physics● Brownian motors
Granular materialsGranular media are systems madeof many “grains” (particles from0.1mm or larger) which loseenergy when interacting. They area fascinating testground for manyrecent theories in out-of-equilibrium statistical physics (seebelow). Here we study thosesystems by numerical simulations,kinetic theories and experiments.You can have a look to our lab atthe ground floor of Fermi Building,Room 012.
Out-of-equilibrium statisticalphysicsEquilibrium statistical physics failsin many systems where currentsand dissipation appear (turbulence,forced fluidodynamics, aggregateof self-propelled particles, opensystems, etc.). Many alternativeapproaches exist, such ashydrodynamics and kinetic theory,e.g. the Boltzmann equation.
Sometimes these systems are also“small” and for this reasonfluctuations can be very large: thetheories of probability, stochasticprocesses, and large deviations,become – therefore - essentialtools.
Brownian motorsThey are small objects that“rectifies” fluctuations, obtainingwork from heat. We study modelsand experimental examples,showing in which (non-equilibrium)conditions such a rectification maybe optimized.
Sapienza unit
Rocco Ruggeri
contacts
e_mail: [email protected]: Area della Ricercaca Sesto F.no Room 71 B
keywords
● Mathematics● Tunneling● Complexity in society,and economics
Macroscopic quantum tunneling
The principle that no signal can travelfaster than the light speed in vacuum isaccepted as one of the basic lawsof nature. Yet, there is no formal proof,based only on Maxwell’s equations, that noelectromagnetic wave packet can travelfaster than the speed of light.
Therefore, there may be a shadow of doubtas to whether this principle istrue in any case . However, the question asto whether a wave packet can beconsidered a signal is a much debatedand complicated one. Superluminal effectsfor evanescent waves have beendemonstrated in tunneling experiments inboth the optical domain and the microwaverange.
Complex systems andeconomic crises.
Economic theory dominant today, knownas the neoclassical synthesis, assumesthat markets are in equilibrium as demandalways equals supply.
The financial crisis which started in early2007 and still not resolved yet, has shownthat the economic and financial system, farfrom being in a state of equilibrium, is,manifestly, in a constant state of instability.
The science of complexity is proving toplay an important role in the modeling ofeconomic events and social phenomena assystems that evolve in the non-equilibrium.
Our goal is to achieve better understandingof the issues outlined above.
Florence unit
Barbara Ruzicka
contacts
Office: Fermi Building, 110
htp://glass.phys.uniroma1.it/ruzicka/
keywords
● Experiments of soft matter systems.● Phase diagram. Gel and glass transitions.● Structure and dynamics of colloids, polymers and bio-soft systems.
Structure and dynamics, phase diagram andgel/glass transitions.Structure and dynamics are investigated throughconventional, synchrotron and neutron techniques.Measurements are performed, in collaboration withDr. R. Angelini (ISC Sapienza), in the Soft MatterLaboratory: Light Scattering, in the Fermi Buildingroom 010, where Dynamic Light Scattering (DLS),Multiangle DLS and Multispeckle DLS techniquesare available (see Figures) and in Large ScaleFacilities such as ESRF and ISIS. Results are compared with theory and simulationin collaboration with Dr. E. Zaccarelli (ISCSapienza).In particular we investigate system different from
common “hard” spheres colloidal ones such as:
Anisotropic colloidal particles.
Charged colloidal suspension of disks of nanometric size with inhomogeneous charge distribution interacting through a directional “patchy like” potential.The phase diagram has been deeply studied offering also the possibility toobserve unconventional arrested states.Nature Materials 5, 4049 (2014); Nature Communications 10, 56 (2011).
Polymeric multiresponsive microgels
Microgels, made by interpenetrated polymer networks, thermo-and pH responsive. Highly used for technological applicationsand example of “soft” colloids partially interpenetrating that areexpected to originate even more complex and fascinating phasediagrams respect to conventional colloids.JNCS 407, 361 (2015); JCP in press (2016).
Multiangle DLS
Multispeckle DLS
Sapienza unit
Antonio Maria Scarfone
contacts
[email protected]: DISAT – Politecnico di Torinohttps://sites.google.com/site/antoniomariascarfonehp/
keywords
● Non-Extensive entropy, power-law distributions● Information geometry● Nonlinear Fokker-Planck equations
Non-Extensive entropy
A wide variety of generalizedentropies, from which probabilitydistributions with power-law tailscan be derived, are investigated onthe epistemological point of view.Potential applications on physicaland physical-like systems areconsidered.
Information geometry
Information geometry is a powerfulframework for studying the familyof probability distributions byapplying the geometric toolsdeveloped in affine differentialgeometry. We apply this formalismto investigate the mathematicalstructure underlying non-extensivestatistical mechanics.
Non-linear Fokker-Planckequations
Irreversible processes described
by Fokker-Planck equations can be
characterized by non-increasing
Lyapunov functional. In non-linear
FPEs Lyapunov functionals are
related with generalized relative
entropies.
publications
● Information geometry on the k-thermostatisticsEntropy 17, 1204
● Basic-deformed thermostatistics J. Phys. A: Math. Theo. 40, 8635
● Entropic forms and related algebras Entropy 15, 624
Sapienza unit
Donatella Schiumarini
contacts
[email protected], Ed. 5, PT. St. 7http://www.mlib.isc.cnr.it/your-details/userprofile/schiumarini.html
keywords
● Linear optical properties of isotropic-anisotropic etherostructures● Exciton-polariton propagation in isotropic-anisotropic multilayers
Linear optical propertiesof isotropic-anisotropicetherostructures
The study intends to individuate thedynamical behavior of the lightpropagation in periodic ethero-structures whose elementary cell isbuilt alternating isotropic slabs withanisotropic ones with in plane opticalaxes mis-oriented among them. Theresulting elementary cell shows spatialasymmetry that strongly affects thepropagating modes of the system andtheir polarization state.
Linear optical propertiesof isotropic-anisotropicetherostructures
In this case the research focuses onsystems showing a periodic mis-orientation of the in plane C_axis andan excitonic resonance in their isotropicpart. As indicated by the opticalresponse reported in the figures for asystem of 128 unitary cells, del
C=pi/2,
exciton energy En=1.418(eV) and forBragg condition along x (TE direction)
the light-exciton interaction behaves astotally absorbing under TM radiationand as totally reflecting under TE, beingalways linear its polarization.
Montelibretti unit
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1.00E+000
1.20E+000
TE pol., N=128
Rfl
Trs
Abs
En (eV)
Inte
nsity
Stefano Selci
Indirizzo mail: [email protected]
●Analisi morfologiche di cellule e tessuti mediante tecniche di microscopia ottica,
confocale ed elettronica ●Analisi spettroscopica uv-vis-nir ● Microscopia a scansione di sonda
Stefano Selci shows strong
competences in experimental solid
state physics, in partcular optcal
spectroscopy and other surface
techniques like scanning probe
microscopies. Later involvements in
some newer optcal techniques or
technological eforts, like instruments
for space missions, in which
nanotechnology competences
acquired within the STM have been
applied, display his great curiosity and
ability to exploit competences in
diferent disciplines. The combinaton
of well proven skills in optcal
spectroscopy and scanning probe
concepts has enabled Stefano Selci to
build a new type of confocal
microscope. The acquisiton of images
with high spatal resoluton X,Y and Z,
typical of any confocal microscope, has
been combined with the hyperspectral
acquisiton of an extended and
contnuous spectrum from the visible
to medium infrared regions.
Stefano Selci is author or co-author of
about 100 papers published in
natonal and internatonal journals
and books, several patents, and has
supervised several theses for degrees
and PhDs in Physics.
He has also organized NATO schools
and has been Editor of Conference
books. He is a regular referee for
internatonal journals (e.g. Journal of
Applied Physics). He has been Adviser
for the Nobel Prize assignment in
Physics (2002).
Tor Vergata unit
contacts
keywords
Polyelectrolyte-induced aggregation of colloidal particles By a combined approach involving dynamic light scattering, electrophoresys and microscopy techniques, we investigatethe self-assembly phenomena occurring in co-suspension ofoppositely charged polyelectrolytes and colloidal particles, as lipid vesicles(liposomes), yielding the formation of a stable cluster phase, where aggregatesshow a novel nano-scaffolded multi-compartmental structure. Fundamental researchon particle-polyion interaction and cluster aggregation mechanisms areaccompanied with applicative studies aimed to develop the high potential of thissystem in bio-nanotechnology, as innovative drug-delivery system, in a strongly
interdisciplinary ambits.
Simona Sennato
contacts
Office: Fermi Building, 412
http://server2.phys.uniroma1.it/gr/PhOBiA/index.html
keywords
● Self-assembly and aggregation in colloidal systems ● Supramolecular structures ● Biological cell membranes and model membrane systems
Biological and model membranesBy means of Langmuir trough, AFMand optical microscopy, we study thes t ruc tu ra l p rop e r t i es o f ce l lmembranes and model membranessystems, as l ipidic mono andbilayers and giant vesicles, with theaim to characterize their organizationwith respect to environmentalparameters and interactions withbiological macromolecules, as drug,proteins or DNA.
Supramolecular structures Novel classes of biological or syntheticamphiphiles and peptides gives rise tosupramolecular structures formed byhierarchical self-assembly. By controlledtuning of the physico-chemical parametersof the system, shape and dynamictransition may be observed.Macroscopically extended and robustnetworks due to gelation fenomena mayform, whose interesting properties openthe way to application as new materials intissue engineering.
Sapienza unit
Vito D.P. Servedio
contacts
[email protected]: Fermi Building, 505http://pil.phys.uniroma1.it/~servedio
keywords
● Opinion Dynamics, Quantitative Linguistics● Citizen Science and Human Computation● Learning Dynamics
The dynamics of correlated novelties
Novelties are commonplace in daily life. They arealso fundamental to the evolution of biologicalsystems, human society, and technology. Byopening new possibilities, one novelty can pave theway for others in a process that Kauffman hascalled “expanding the adjacent possible”.
The Web has progressively acquired the status of aninfrastructure for social computation allowing researchers tocoordinate the cognitive abilities of human agents bysteering the collective user activity towards predefinedgoals. This general trend is triggering the adoption of web-games as a very interesting laboratory to run experimentswhenever the contribution of human beings is cruciallyrequired for research purposes.
Each sphere of knowledge could be depicted as a networkof correlated items. By properly exploiting theseconnections, innovative and more efficient learningstrategies could be defined, possibly leading to a fasterlearning process and an enduring retention of information.
Statistical modeling of learning paths
Web-based social computation
http://www.xtribe.eu
F. Tria et al., Sci.Rep. 4, 5890 (2014)
Sapienza unit
Alessandro Torcinicontacts
[email protected]: ISC/CNR, via Madonna del Piano, 10, B120http://wwwold.fi.isc.cnr.it/users/alessandro.torcini/
keywords
● Nonlinear Dynamics● Computational Neuroscience● Synchronization
Computational NeuroscienceLab
http://neuro.fi.isc.cnr.it/
The lab is active in Florence since 2006 and itis presently composed of 2 permanentresearchers, 3 post-docs and 2 PhD students. The studied subjects range from the dynamicsof single neurons, to the emergence ofcollective activity in neural networks to dataanalysis of neural time series, mainly spiketime series. The group has published morethan 50 scientific articles in the last 8 yearsand it has been supported by researchfundings for more than 1 million euros in thelast 4 years obtained from the EuropeanUnion, the Italian Ministry of Foreign Affairs(MAE), the German Max-Planck-Gesellschaft,and the Italian Ministry of University andResearch. The group maintains activeinternational collaborations with the followinginstitutions: University of Aarhus (Denmark),Ecole Normale Superieure, Paris (France),University of Bonn (Germany), Tel AvivUniversity (Israel), University Pompeu Fabra,Barcelona (Spain), University of Aberdeen,University of Bristol, Imperial College London(UK), University of Michigan, University ofCalifornia San Diego (USA). The Lab is theitalian hub of the Joint Italian-Israeli Laboratoryin Neuroscience (2010-2019) supported byMAE.
Luccioli, Olmi, Politi, Torcini PRL (2012)Mikkelsen, Imparato Torcini PRL (2013)
Synchronization
Synchronization is an ubiquitous phenomenonobservable in many fields of science rangingfrom fireflies populations to neural systems,from electrical power-grids to fish banks. Ouraim is to analyze such a phenomenon from thepoint of view of out-of-equilibrium statisticalmechanics and by employing tools originatingfrom nonlinear dynamics. Recently weaddressed the problem of the synchronizationof two populations of phase oscillators withinertia, discovering new peculiar dynamicalstates: Chaotic Chimeras. These statesdisplay a broken simmetry where onepopulation is fully synchronized, while theother population is chaotic. Furthermore thesestates have been observed experimentally incoupled mechanical pendula.
M. Baer, E. Schoell, A. Torcini, Angew. Chem.Int. Ed (2012)Olmi, Martens, Thutupalli, Torcini PRE (2015)
Florence unit
Bruno Tiribilli
contacts
[email protected]: Area di Ricerca CNR – Building B room 134http://www.fi.isc.cnr.it/people/userprofile/bruno_tiribilli.html
keywords
● Atomic Force Microscopy● Biophysics ● Applied physics
Atomic force microscopy Since its invention in 1986, AFM, has beenwidely used for investigating materialcharacteristics at nanoscale level, and itsimprovement has rapidly led to reliableinstrumentation. Although, after more thetwenty years new imaging methods are stillunder investigation to improve imagequality and speed, new probes soundmore physical property of the sample andthe fields of application are still growing.For example a new kind of probefabricated by carving a cantilever at theend of a fiber is capable to detect forcesand optical tunneling signals at the sametime.
Self-driven cantilever oscillationA non-linear control of cantilever oscillationamplitude dynamically adjust the gain ofthe self-sustained vibrat ion of thecantilever. This new dynamic modeimproves scan speed and image accuracyit results particularly effective when sharpedges are present on the surface and onsoft materials, like biological samples.
Diffusion of two molecular speciesin a crowded environment.
Diffusion of two fluids is studied in theframe of differential equations derived froma well defined microscopic model wherecrowding and steric interference are takeninto account. The experiment of two inkdrops simultaneously evolving in acontainer filled with water shows thatmolecular crowding results in the formationof a dynamical barrier that prevents themixing of the drops. This phenomenon issuccessfully captured by the model.
Florence unit
Lorenzo Ulivi
contacts
[email protected]: ISC-CNR, Via Madonna del piano 10, SestoFiorentino, room B164, tel: 055 522 6664http://www.fi.isc.cnr.it/people/userprofile/uliviiscfi.html
keywords
● Hydrogen storage, clathrate-hydrates ● Materials at high pressure, Diamond Anvil Cell● Neutron scattering, Raman and Infrared spectroscopy
Hydrogen Clathrate Hydrates
Clathrate-hydrates are solid compoundsmade of water and other “guest”molecules, which are trapped in polyhedralcavities (cages). They are ubiquitous innature . We syn thes ize hydrogenclathrate-hydrates (having differentstructures) in the laboratory, using apressure higher than 1 kbar. Thesecompounds are important for hydrogenstorage but we are interested also in thequantum dynamics of the hydrogen (H
2, D
2
or HD) in the cage, which we study withNeutron or Raman spectroscopy. Thespectrum of the excitations comprisemolecular rotations, center-of-massquantum excitation (rattling) and a l lpossible combinations of these. Positionand intensity may be calculated withquantum codes, and compared withneutron experiments. An example for HD isin figure.
Hydrophobic Solvation
Hydrophobic gases have very lowsolubility in liquid water. In solid clathrate,hydrogen/water ratio is about 25 %.Preliminary to the study of hydrogenclathrate formation from the H
2-H
2O liquid
solution, we have studied, by means ofRaman scattering, the solubility and thespectroscopic features of the H
2 molecule
in water up to 3000 bar. It increases withpressure, but it never reaches valuessimilar to those obtained in clathrates.
Florence unit
Paola Verrucchi
contacts
[email protected] 337, Physics Department - University of FlorenceVia G.Sansone 1, Sesto Fiorentino (FI)
http://www.fi.isc.cnr.it/people/userprofile/verrucchi.html
keywords
● Open Quantum Systems● Quantum Information and Computation● Low-dimensional magnetic systems
Dynamics of open quantumsystemsThe first step in the study of physical phenomenais that of identifying the system upon which tofocus the attention, usually referred to as the”principal system”. What is left out might yetcontain parts that significantly affect the processunder analysis, and combine to define the”environment”. Quantum systems with anenvironment generally go under the name of OpenQuantum Systems (OQS). The core problem in studying OQS is that ofconsidering how principal system and environmentcommunicate and interplay during the quantumevolution induced by their mutual interaction. Infact, due to correlations that dynamically set upbetween the two subsystems, their respectivedynamics not only stops being unitary, but it alsogets a memory that wipes out markovianity even inthe absence of random processes or phenomenaotherwise needing a statistical approach. In fact, itis just the entanglement, i.e. the most genuinelyquantum type of correlation, that mediates theinformation exchange between principal systemand environment, insofar causing non-markovianityto emerge as a striking feature of the principalsystem’s evolution, and one of the pivotal issues inthe theory of OQS dynamics.In this general framework we specificallyconcentrate our attention upon these cases:1) When the environment is a many-body quantumsystem:-> Quantum communication.2) When the environment is an apparatus:->Quantum measurements and control.3) When the environment is a complex system:->Finite-temperature quantum effects inthermodynamic, chemical, and possibly biological
processes.
Spin chains in quantumcommunicationQuantum devices are eclectic objects whosearchitecture varies greatly depending on theirspecific purpose and, perhaps primarily, on theway they are physically realized. However, thereare some basic requirements that are most oftenassumed, amongst which the possibility ofinitializing the input quantum register, whichimplies that of individually addressing, andpossibly manipulating each single qubit.When solid-state implementations are considered,with qubits embodied in the spin degrees offreedom of molecules embedded in crystallinematrices or deposited on layered substrates,individual qubit addressing can be obtained byconveying a signal through a functional wire, asqualitatively shown in figure. In particular, we studyschemes where the wire is modeled by a spin-chain (i.e. by a one-dimensional magnetic system)and proper signals are embodied in magneticsolitons (i.e. in nonlinear excitations of spinchains), known for being localized, both in spaceand time, and robust against perturbations, whichguarantee that each signal will travel down to thequbit without distortion.
figure
Florence unit
Ruggero Vaiacontacts
[email protected]: building B, room 129http://fox.fi.isc.cnr.it/users/ruggero.vaia/vaia.htm
keywords
● Theory of low-dimensional magnetic systems● Optimal transport in one-dimensional quantum and classical channels● Quantum effects in low-dimensional systems
Transport in 1D channels
At variance with their continuous case,one-dimensional arrays are intrinsicallydispersive: an injected wavepacket is notfaithfully transmitted, but looses itscoherence. However, if the array's bonds(i.e., sping constants, hoppingamplitudes,...) are properly tuned,dispersion can be limited or eveneliminated. This is relevant, e.g., in thecase of the transfer of quantum statesbetween distant qubits, which is one of thebasic tasks that a quantum computerbased on qubits located on fixed positionshas to accomplish. Obtaining perfecttransmission is theoretically possible at thecost of tuning all the systems bonds, aproblematic task for a real experiment. Ananalysis of the transport mechanism leadsto the concept of quasi-perfecttransmission, that can be reached to highdegree by only acting on few extremalbonds. The space-time evolution of apropagating excitation injected in the firstsite of a N=250-site open array is shown inthe figure: the optimization of just twobonds at the chain ends, j
1=2N-1/3 and
j2=1.6N-1/6, leads to an efficiency that is still
larger than 98.7% in the large N limit.The same optimization problem is morecomplicated for a classical system.
A quantum Newton's cradle
The proposal consists in a system of atomswith two internal states trapped in a one-dimensional tube with a longitudinal opticallattice; the atoms are maintained in astrong Tonks–Girardeau regime atmaximal filling. A localized endpointdisturbance of the wave-functionpropagates along the chain in analogy withthe propagation of momentum in theclassical Newton cradle. The quantumtraveling signal is generally deteriorated bydispersion, e.g., for a chain with uniformbonds and is known to be zero for suitablyengineered bonds, but the latter is hardlyrealizable in practice. Starting from theseopposite situations it has been shown howthe coherent behavior can be enhancedwith minimal experimental effort.
figure
Florence unit
Massimiliano Viale
contacts
[email protected]: Fermi Building, Room 414, Floor4th
http://www.sapienza.isc.cnr.it/your-details/userprofile/126.html
keywords
● Collective Behavior in Biological Systems● (Non-Equilibrium) Statistical Mechanics● Inference, Modeling & Simulations
From bird flocks to fish schools, from insect swarms tocell colonies, collective behaviour is a very widespreadphenomenon in many biological systems.It is hard to define, but easy to recognize. What are the mechanisms regulating collective behaviourin biological systems?
The aim of my work is to understand the collective behaviourexhibited by flocks of starlings (Sturnus vulgaris) and swarmsof non-biting midges (Chironomidae) through the analysis ofsynchronized high speed image sequences from threecameras.Using stereo matching and other computer vision techniques,we are able to reconstruct, in three dimensions, thetrajectories of individual animals within the aggregation.Further analysis of the trajectories should lead to a betterunderstanding of the fundamental interaction rules betweenindividuals.
- Information transfer and behavioural inertia in starling flocks Nature Physics 10 (9), 691-696
- Interaction ruling animal collective behavior depends on topological rather than metric distance: Evidence from a field study Proceedings of the National Academy of Sciences 105 (4), 1232-1237
- Collective Behaviour without Collective Order in Wild Swarms of Midges PloS Computational Biology 10 (7), e1003697
Experiments find coherent information transfer throughbiological groups on length and time scales distinctlybelow those on which asymptotically correcthydrodynamic theories apply.
We need a new continuum theory of collective motion couplingthe velocity and density fields to the inertial spin field recentlyintroduced to describe information propagation in naturalflocks of birds.
- Silent Flocks arXiv:1410.2868
Which is the "recipe" that exactly reproduces the real biological systems? Which are the hypotheses cut by the "Occam's Razor" for which "entities must not be multiplied beyond necessity"?
Biological data have hidden information to be gathered: wehave to solve the "Inverse Problem".We can try to take advantage of the critical aspects ofbiological systems because in physics this is synonymous ofphase transition and scale invariance.A deeper statistical mechanics insight allows us to "rescale"biological data from different eventsand obtain more robust and meaningful answers.It is required a complex and interdisciplinary line of researchthat includes:
- Deep theoretical expertise on statistical physics of complexsystems ;- Bayesian inference on biological data;- Optimization – Simulations - Modeling ;
- Scale-free correlations in starling flocks Proceedings of the National Academy of Sciences 107 (26), 11865-11870
- Statistical mechanics for natural flocks of birds Proceedings of the National Academy of Sciences 109 (13), 4786-4791
Sapienza unit
Emanuela Zaccarelli
contacts
[email protected]: Fermi Building, 106http://glass.phys.uniroma1.it/Emanuela/
keywords
● Simulation and theory of soft matter systems● Gel and glass transitions● Complex effective interactions: novel phases and anomalous dynamics
Complex effective interactions
Colloidal particles can be treated as super-atoms moving in a continuum (solvent) in theframework of statistical mechanics. Theyinteract with effective potentials that can betuned arbitrarily by changing the properties ofthe particle (e.g. shape, architecture,heterogenous surface) or by varying externallythe conditions of the solutions in which theyare suspended. In this way, they experienceinteractions and show phenonema that are notfound in atomic or molecular systems.
The simplest way to control the interactionsbetween colloids is to add smaller particles(cosolute) in the solution, which originate so-called depletion interactions. By tuning theproperties of the co-solutes, novel effects canbe found. For example a co-solute close to itspercolation transition induces so-calledCasimir-like forces on the colloids.
N.Gnan, E. Zaccarelli, F.Sciortino NatureCommunications 5, 3267 (2014)
Gels and Glasses
By tuning effective interactions, we find notonly new thermodynamic phases (e.g. crystalswith unconventional lattice spacings) but alsodifferent types of disordered arrested states: Gels where particles are organized intonetworks and Glasses where particles areblocked by their neighbours.
Recently, we discovered equilibrium gelsformed by patchy particles, which wereexperimentally observed in colloidal clays. Thiswork, done in collaboration with ISCexperimental researchers B. Ruzicka and R.Angelini, has also revealed the possibility ofother unconventional glasses with partiallyfrozen orientational degrees of freedom(R. Angelini, E. Zaccarelli, F. de MeloMarques, M. Sztucki, A. Fluerasu, G. Ruoccoand B. Ruzicka, Nat. Comm. 5, 3267 2014).
Nowadays we are working on microgelparticles, made by crosslinked polymernetworks, which are thermo-responsive toelucidate the nature of their arrested states atultra-high densities.
Sapienza unit
Andrea Zaccaria
contacts
Email: [email protected]: Fermi Building, room 206
keywords
● Complex Networks● Agent Based Models● Financial time series
Concepts and tools borrowed bystatistical mechanics and complexitycan be used to invest igate theproperties of financial time series. Recently we have shown that non trivial memory effects are present in the pricedynamics of stocks [1] and that extremeevents lead to a power law relationbetween skewness and kurtosis, that isva l id a lso fo r the s ta t i s t i cs o fearthquakes [2].
[1] Garzarelli et al. Scientific reports 4 (2014).[2] Cristelli et al. Physical Review E 85.6 (2012):066108.
Is there a common path on countries’development, or each country mustfollow his own way? In order to produce cars, one has to learn before how toproduce wheels? The theory ofcomplex networks can be applied toanswer these questions and describethe industrialization of countries.Starting from the empirical data aboutthe worldwide exports we have built anetwork of products that are connectedby a directed link if there is a causalityrelationship between them. We cansuggest paths in the product spacewhich are easier to achieve, drivingcount r ies ’ po l i c ies dur ing the i rindustrialization.
Agent based models represent an alternative to the standard economic theory,which assumes perfect rationality and information. The consequences of therelaxation of these assumptions can be studied by numerical simulations in whichtraders buy or sell stocks in a virtual financial market, following personal or collectivestrategies. These models can reproduce the main statistical features of pricedynamics.
Zaccaria et al." H o w t h et a x o n o m y o fproducts drivesth e e c o n o m i cdevelopment ofcountries." PloSone 9.12 (2014):e113770.
Sapienza unit
![BRIAN A. ANGELINI, ESQ. [SBN 234072]](https://img.pdfslide.us/doc/110x75/61dbf9e5ad7db112d73d6153/brian-a-angelini-esq-sbn-234072.jpg)
