The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once.

The widely
accepted age of the universe, as estimated by general relativity, is 13.8
billion years.

In the beginning, everything in existence is thought to have occupied a single infinitely dense point, or singularity. Only after this point began to expand in a "Big Bang" did the universe officially begin.

In the beginning, everything in existence is thought to have occupied a single infinitely dense point, or singularity. Only after this point began to expand in a "Big Bang" did the universe officially begin.

Although the
Big Bang singularity arises directly and unavoidably from the mathematics of
general relativity, some scientists see it as problematic because the math can
explain only what happened immediately after—not at or before—the singularity.

"The Big Bang singularity is the most serious problem of general relativity because the laws of physics appear to break down there," Ahmed Farag Ali at Benha University and the Zewail City of Science and Technology, both in Egypt, told Phys.org.

Ali and
coauthor Saurya Das at the University of Lethbridge in Alberta, Canada, have
shown in a paper published in Physics Letters B that the Big Bang singularity
can be resolved by their new model in which the universe has no beginning and
no end.

**Old ideas revisited**
The
physicists emphasize that their quantum correction terms are not applied ad hoc
in an attempt to specifically eliminate the Big Bang singularity. Their work is
based on ideas by the theoretical physicist David Bohm, who is also known for
his contributions to the philosophy of physics.

Starting in the 1950s, Bohm explored replacing classical geodesics (the shortest path between two points on a curved surface) with quantum trajectories.

Starting in the 1950s, Bohm explored replacing classical geodesics (the shortest path between two points on a curved surface) with quantum trajectories.

In their
paper, Ali and Das applied these Bohmian trajectories to an equation developed
in the 1950s by physicist Amal Kumar Raychaudhuri at Presidency University in
Kolkata, India. Raychaudhuri was also Das's teacher when he was an
undergraduate student of that institution in the '90s.

Using the
quantum-corrected Raychaudhuri equation, Ali and Das derived quantum-corrected
Friedmann equations, which describe the expansion and evolution of universe
(including the Big Bang) within the context of general relativity. Although
it's not a true theory of quantum gravity, the model does contain elements from
both quantum theory and general relativity. Ali and Das also expect their
results to hold even if and when a full 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 possible
fate of the universe is that it starts to shrink until it collapses in on
itself in a big crunch and becomes an infinitely dense point once again.

Ali and Das
explain in their paper that their model avoids singularities because of a key
difference between classical geodesics and Bohmian trajectories. Classical
geodesics eventually cross each other, and the points at which they converge
are singularities. In contrast, Bohmian trajectories never cross each other, so
singularities do not appear in the equations.

In
cosmological terms, the scientists explain that the quantum corrections can be
thought of as a cosmological constant term (without the need for dark energy)
and a radiation term. These terms keep the universe at a finite size, and
therefore give it an infinite age. The terms also make predictions that agree
closely with current observations of the cosmological constant and density of
the universe.

**New gravity particle**
In physical
terms, the model describes the universe as being filled with a quantum fluid.
The scientists propose that this fluid might be composed of
gravitons.

hypothetical massless particles that mediate the force of gravity. If they exist, gravitons are thought to play a key role in a theory of quantum gravity.

hypothetical massless particles that mediate the force of gravity. If they exist, gravitons are thought to play a key role in a theory of quantum gravity.

In a related
paper, Das and another collaborator, Rajat Bhaduri of McMaster University,
Canada, have lent further credence to this model. They show that gravitons can
form a Bose-Einstein condensate (named after Einstein and another Indian
physicist, Satyendranath Bose) at temperatures that were present in the
universe at all epochs.

Motivated by
the model's potential to resolve the Big Bang singularity and account for dark matter and dark energy, the physicists plan to analyze their model more
rigorously in the future. Their future work includes redoing their study while
taking into account small inhomogeneous and anisotropic perturbations, but they
do not expect small perturbations to significantly affect the results.

"It is satisfying to note that such straightforward corrections can potentially resolve so many issues at once,"Das said.

I think, the Density waves are causing the Time... Also, there should be new propagated waves of this kind by expansion, with every Planck Time period.

ReplyDeleteWe determine the duration of time according to how many of them have passed.