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No Big Bang? Quantum equation predictsuniverse has no beginning9
February 2015, by Lisa Zyga
This is an artist's concept of the metric expansion ofspace,
where space (including hypothetical non-observable portions of the
universe) is represented ateach time by the circular sections. Note
on the left thedramatic expansion (not to scale) occurring in
theinflationary epoch, and at the center the expansionacceleration.
The scheme is decorated with WMAPimages on the left and with the
representation of stars atthe appropriate level of development.
Credit: NASA
(Phys.org) The universe may have existedforever, according to a
new model that appliesquantum correction terms to
complementEinstein's theory of general relativity. The modelmay
also account for dark matter and dark energy,resolving multiple
problems at once.
The widely accepted age of the universe, asestimated by general
relativity, is 13.8 billion years.In the beginning, everything in
existence is thoughtto have occupied a single infinitely dense
point, orsingularity. Only after this point began to expand ina
"Big Bang" did the universe officially begin.
Although the Big Bang singularity arises directlyand unavoidably
from the mathematics of generalrelativity, some scientists see it
as problematicbecause the math can explain only what
happenedimmediately afternot at or beforethe singularity.
"The Big Bang singularity is the most seriousproblem of general
relativity because the laws ofphysics appear to break down there,"
Ahmed FaragAli at Benha University and the Zewail City ofScience
and Technology, both in Egypt, told Phys.org.
Ali and coauthor Saurya Das at the University ofLethbridge in
Alberta, Canada, have shown in apaper published in Physics Letters
B that the BigBang singularity can be resolved by their newmodel in
which the universe has no beginning andno end.
Old ideas revisited
The physicists emphasize that their quantumcorrection terms are
not applied ad hoc in anattempt to specifically eliminate the Big
Bangsingularity. Their work is based on ideas by thetheoretical
physicist David Bohm, who is alsoknown for his contributions to the
philosophy ofphysics. Starting in the 1950s, Bohm exploredreplacing
classical geodesics (the shortest pathbetween two points on a
curved surface) withquantum trajectories.
In their paper, Ali and Das applied these Bohmiantrajectories to
an equation developed in the 1950sby physicist Amal Kumar
Raychaudhuri atPresidency University in Kolkata, India.Raychaudhuri
was also Das's teacher when he wasan undergraduate student of that
institution in the'90s.
Using the quantum-corrected Raychaudhuriequation, Ali and Das
derived quantum-correctedFriedmann equations, which describe
theexpansion and evolution of universe (including theBig Bang)
within the context of general relativity.Although it's not a true
theory of quantum gravity,
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the model does contain elements from bothquantum theory and
general relativity. Ali and Dasalso expect their results to hold
even if and when afull theory of quantum gravity is formulated.
No singularities nor dark stuff
In addition to not predicting a Big Bang singularity,the new
model does not predict a "big crunch"singularity, either. In
general relativity, one possiblefate of the universe is that it
starts to shrink until itcollapses in on itself in a big crunch and
becomesan infinitely dense point once again.
Ali and Das explain in their paper that their modelavoids
singularities because of a key differencebetween classical
geodesics and Bohmiantrajectories. Classical geodesics eventually
crosseach other, and the points at which they convergeare
singularities. In contrast, Bohmian trajectoriesnever cross each
other, so singularities do notappear in the equations.
In cosmological terms, the scientists explain thatthe quantum
corrections can be thought of as acosmological constant term
(without the need fordark energy) and a radiation term. These
termskeep the universe at a finite size, and therefore giveit an
infinite age. The terms also make predictionsthat agree closely
with current observations of thecosmological constant and density
of the universe.
New gravity particle
In physical terms, the model describes the universeas being
filled with a quantum fluid. The scientistspropose that this fluid
might be composed ofgravitonshypothetical massless particles
thatmediate the force of gravity. If they exist, gravitonsare
thought to play a key role in a theory ofquantum gravity.
In a related paper, Das and another collaborator,Rajat Bhaduri
of McMaster University, Canada,have lent further credence to this
model. Theyshow that gravitons can form a Bose-Einsteincondensate
(named after Einstein and anotherIndian physicist, Satyendranath
Bose) at
temperatures that were present in the universe at allepochs.
Motivated by the model's potential to resolve theBig Bang
singularity and account for dark matterand dark energy, the
physicists plan to analyzetheir model more rigorously in the
future. Theirfuture work includes redoing their study while
takinginto account small inhomogeneous and
anisotropicperturbations, but they do not expect smallperturbations
to significantly affect the results.
"It is satisfying to note that such straightforwardcorrections
can potentially resolve so many issuesat once," Das said.
More information: Ahmed Farag Ali and SauryaDas. "Cosmology from
quantum potential." PhysicsLetters B. Volume 741, 4 February 2015,
Pages276279. DOI: 10.1016/j.physletb.2014.12.057.Also at:
arXiv:1404.3093[gr-qc].
Saurya Das and Rajat K. Bhaduri, "Dark matter anddark energy
from Bose-Einstein condensate",preprint:
arXiv:1411.0753[gr-qc].
2015 Phys.org
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APA citation: No Big Bang? Quantum equation predicts universe
has no beginning (2015, February 9)retrieved 12 February 2015 from
http://phys.org/news/2015-02-big-quantum-equation-universe.html
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