Major Issues in Nuclear Physics Aided by Massive Computation

Forefront Questions in Nuclear Science and the Role of High Performance Computing

January 26-28, 2009 · Washington D.C.

Major Issues in Nuclear Physics Aided by Massive Computation

David B. Kaplan ~ Institute for Nuclear Theory

The challenge of nuclear theory

• Many-body problem of interaction nucleons• Quantum mechanical• Strongly interacting

pre- 1970s ~ phenomenological models:

Predictive phenomenology; qualitative theoretical understanding

The challenge of nuclear theory

• Many-body problem of interaction nucleons• Quantum mechanical• Strongly interacting

pre- 1970s ~ phenomenological models:

Predictive phenomenology; qualitative theoretical understanding

• A simply expressed, complete theory of the strong interactions• Nucleons are bound state of quarks & gluons• Quantum mechanical• Strongly interacting• Relativistic

post-1970s ~ Quantum Chromodynamics (QCD):

1980’s, 1990’s: a ferment of ideas

Exchange of ideas with particle theory:• Effective field theory• String theory• Symmetries

Experiments:• Precision symmetry tests• SN 1987A• Neutrino masses• RHIC, JLab• Trapped atoms...

Exchange of ideas withcondensed matter & atomic theory:• Quantum chaos• Density functional theory• Color superconductivity of quark matter

5th ANL/MSU/JINA/INT FRIB Workshop: Bulk Nuclear Properties Nov. 19 - 22, 2008

Workshop on Relativistic Dynamics of Graphene Jan. 8 - 11, 2008

Nuclear Interactions at Ultra-high Energy in Light of Recent Results from Auger Feb. 20 - 22, 2008

From Strings to Things: String Theory Methods in QCD and Hadron Physics March 24 - June 6, 2008

Soft Photons and Light NucleiJune 16-20, 2008

The QCD Critical PointJuly 28 - Aug. 22, 2008

Low Energy Precision Electroweak Physics in the LHC EraSept. 22 - Dec. 5, 2008

Atomic, Chemical, and Nuclear Developments in Coupled Cluster Methods June 23-July 25, 2008

The diversity of nuclear theory: INT programs 2008

2000’s: Computational nuclear physics comes of age

• Lattice QCD• Advances in the shell model• Density functional methods• Coupled cluster techniques...



Experience from TFlops-years: a glimpse of a unified nuclear theory grounded in QCD, aided by extreme computing


Structure: from quarks and gluons to heavy nuclei




Structure: from quarks and gluons to heavy nuclei

Dynamics: evolution of the quark gluon plasma in a heavy ion collision; fusion and fission processes which power stars and create elements; the cataclysmic explosions of stars



Origins

Fusio

nMeta

ls

Supe

rnova

Collapse

The extreme computing opportunities and challenges for nuclear physics all come together in describing the life of a star

Origins

Nucleons, resonances

Quark-gluon plasma

Matter/anti-matter annihilation

Exascale challenges:

QCD phase diagram

Structure of the nucleon & resonances

Clues about origin of matter/anti-matter asymmetry

Origins

Phase diagrams: Water...

...primarily explored in the laboratory

Origins

Phase diagrams: QCD (an educated guess!)...

...to be explored by accelerator, telescope & computer

Origins



Observation

Origins



Observation

Origins

Experiment &EXASCALE

Computation



Observation

EXASCALE Computation

Origins

Experiment &EXASCALE

Computation

Origins

Recreating the Big Bang in heavy ion collisions

Experimental program: RHIC, LHCTheory challenge: a unified description of a heavy ion collisions

Origins



Initial conditions: quark/gluon distribution in ions

Origins




Thermalization; quark-gluon plasma

Origins





Expansion and hadronization

Origins






Relativistic hydrodynamics

Origins







Departure from thermal equilibrium

Origins








Predicting observables

Origins









• Important physics• Ambitious computation

EXASCALE?

Origins









• Important physics• Ambitious computation

Origins

Quark & gluon structure of nucleons and resonancesfrom lattice QCD

Experimental program: JLabTheory challenges:

Origins


• What is the momentum distribution of quarks and gluons within the nucleon?


Origins



Structure functions, strange quark content


Origins




• How do currents couple to the nucleon?


Origins




• How do currents couple to the nucleon? High precision form factors (gA to <1%?)


Origins




• How do currents couple to the nucleon? High precision form factors (gA to <1%?)

• Predict exotic states (glueballs, hybrid mesons)


Big Bang:Why is there more matter than anti-matter today?

A key ingredient: violation of baryon number or lepton number symmetryOrigins


A key ingredient: violation of baryon number or lepton number symmetryOrigins

Neutrino-less double beta decay = lepton violation

• Subject of intense experimental search • Requires calculation of nuclear matrix

element

Experimental program: Majorana, Cuore, EXO, NEMO3...Theory challenges:


A key ingredient: violation of baryon number or lepton number symmetry

The structure of 76Ge, 150Nd and calculation of relevant matrix element is an Exascale problem

EXASCALE

Origins

Neutrino-less double beta decay = lepton violation

• Subject of intense experimental search • Requires calculation of nuclear matrix

element

Experimental program: Majorana, Cuore, EXO, NEMO3...Theory challenges:

Fusio

n

Extreme computing: the era for understanding and predicting nuclear reaction rates

Solar fusion:Exascale era: solar fusion rates can be obtained directly from QCD

Fusion

Technique: “Lattice QCD”• Quarks & gluons interacting on a

spacetime lattice.

• Highly parallelizable.

Fusion


spacetime lattice.


• High precision nucleon form factors (e.g. gA to <1%?)

• High precision 2-body forces• Calculation of 3- and 4-body forces

directly from QCDeg: energy levels of four neutrons in a box: not accessible experimentally

e-

Fusion


spacetime lattice.


EXASCALE

• High precision nucleon form factors (e.g. gA to <1%?)

• High precision 2-body forces• Calculation of 3- and 4-body forces

directly from QCDeg: energy levels of four neutrons in a box: not accessible experimentally

e-

Fusion

Metals

Metals

3- and 4-nucleon interactions from lattice QCD

Ab initio nuclear structure & reaction calculations

• GFMC• No-core shell model...

The output from one class of extreme computations feeds into the next:

EXASCALE

Metals

Metals

Triple alpha process

O16

Alpha capture on p-shell nuclei

Metals


O16

Alpha capture on p-shell nuclei

EXASCALE

Metals


Supe

rnova

Super-nova

Cataclysmic events in the heavens

Type I SN: thermonuclear explosion; key distance marker for astronomers

Type II SN: core collapse; origin of heavy elements, neutron stars. Neutrinos play a leading role.

X-ray bursters, colliding neutron stars...

Super-nova

EXASCALE nuclear astrophysics:

• Realistic 3D simulations of core-collapse SN; expect to uncover robust explosion mechanism

• 3D simulations of Type I SN including turbulence effects

• Pulsar & magnetar simulations

Super-nova

Type II Supernovae are the site for synthesis of heavy elements (“r-process”)

Super-nova


Density functional theory:• Compute shell structure along r-process path• Compute shell structure around 100Sn• Provide microphysical theory of fission

Super-nova



FRIB:• Experimental studies of

neutron-rich isotopes

Super-nova


Supernova simulations:• Predict element

abundances• Predict terrestrial

neutrino flux




Super-nova


Supernova simulations:• Predict element

abundances• Predict terrestrial

neutrino flux


EXASCALE



Super-nova

Dynamics from density functional theory:

• Evolution of fissioning nuclei from a microphysical Hamiltonian

• Prediction for distribution of fission products

Collapse

One of the biggest challenges: extended matter at nuclear densities and higher, from QCDCollapse



Present approaches: nuclear matter from QCD is an exponentially hard problem...NOT Exascale-ready

EXASCALE

However: an important piece of the problem can be addressed

Exotic phases at high density all involve the strange quark

Collapse

Lattice QCD: precision studies of nucleon-hyperon interactions

However: an important piece of the problem can be addressed

Exotic phases at high density all involve the strange quark

Collapse

Lattice QCD: precision studies of nucleon-hyperon interactions

EXASCALE!

Will we be ready?

What does it take?

• Can the physics problem productively consume a PFlops-year today?

• Is significant progress expected from an ExaScale machine?

• Does significant progress require an ExaScale machine?







QCD: lattice studies of cold matter & nuclei with A>5








QCD: hydrodynamics of heavy ion collisions; lattice QCD determination of critical point





QCD: hydrodynamics of heavy ion collisions; lattice QCD determination of critical pointStructure: time-dependent density functional studies of fission, reactions










QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;






QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;Astro: Major advances in supernova simulations






QCD: lattice studies of nucleon properties, nucleon-meson interactions, multi-nucleon states & matrix elements, hot quark-gluon plasma, hadronic excited states, hyperons;Astro: Major advances in supernova simulationsNuclear structure: Major advances in nuclear structure calculations using GFMC, no-core shell model, DFT



What nuclear theory challenges could efficiently use an Exascale computer today?


None.

To realize extreme computing in nuclear physics requires minds as well as machines


None.

To realize extreme computing in nuclear physics requires minds as well as machines


None.

• Theory: effective field theory techniques, algorithm development, new formulations of old problems, improved Hamiltonians...

• Computer science: algorithm development, exploiting multi-core chips, parallel architecture, stability with imperfect hardware...

GETTING READY FOR EXASCALE

• Programs such as SciDAC (DOE) and CDI (NSF) have a big role to play



•Access to time on machines of varying sizes is critical: local TFlops clusters to PFlops national class platforms



•Access to time on machines of varying sizes is critical: local TFlops clusters to PFlops national class platforms

•Topical collaborations (2007 Long Range Plan recommendation) would be invaluable for computational nuclear theory


Recap

WITH - AND ONLY WITH - EXASCALE:

Recap


•A unified nuclear theory, from QCD to heavy nuclei

Recap



•Nucleon and nuclear structure becomes a precision science, complementing major experimental programs (~1% errors)

Recap



•Nucleon and nuclear structure becomes a precision science, complementing major experimental programs (~1% errors)

•A new era for the simulation & prediction of nuclear dynamics and reactions from fundamental interactions (fission, fusion, stellar explosions, heavy ion collisions..)

Documents

Major Issues in Nuclear Physics Aided by Massive Computation