What Happened Before the Big Bang?
http://www.physorg.com/news102516861.html
What Happened Before the Big Bang?
Spreading through a bounce: A state that initially has small fluctuations
(left) bounces and develops larger fluctuations (right). Time proceeds along
the horizontal axis, with the volume plotted vertically. Credit: Martin
Bojowald, Penn State
New discoveries about another universe whose collapse appears to have given
birth to the one we live in today will be announced in the early on-line
edition of the journal Nature Physics on 1 July 2007 and will be published
in the August 2007 issue of the journal's print edition.
"My paper introduces a new mathematical model that we can use to derive new
details about the properties of a quantum state as it travels through the
Big Bounce, which replaces the classical idea of a Big Bang as the beginning
of our universe," said Martin Bojowald, assistant professor of physics at
Penn State. Bojowald's research also suggests that, although it is possible
to learn about many properties of the earlier universe, we always will be
uncertain about some of these properties because his calculations reveal a
"cosmic forgetfulness" that results from the extreme quantum forces during
the Big Bounce.
The idea that the universe erupted with a Big Bang explosion has been a big
barrier in scientific attempts to understand the origin of our expanding
universe, although the Big Bang long has been considered by physicists to be
the best model.
As described by Einstein's Theory of General Relativity, the origin of the
Big Bang is a mathematically nonsensical state -- a "singularity" of zero
volume that nevertheless contained infinite density and infinitely large
energy. Now, however, Bojowald and other physicists at Penn State are
exploring territory unknown even to Einstein -- the time before the Big
Bang -- using a mathematical time machine called Loop Quantum Gravity.
This theory, which combines Einstein's Theory of General Relativity with
equations of quantum physics that did not exist in Einstein's day, is the
first mathematical description to systematically establish the existence of
the Big Bounce and to deduce properties of the earlier universe from which
our own may have sprung. For scientists, the Big Bounce opens a crack in the
barrier that was the Big Bang.
"Einstein's Theory of General Relativity does not include the quantum
physics that you must have in order to describe the extremely high energies
that dominated our universe during its very early evolution," Bojowald
explained, "but we now have Loop Quantum Gravity, a theory that does include
the necessary quantum physics." Loop Quantum Gravity was pioneered and is
being developed in the Penn State Institute for Gravitational Physics and
Geometry, and is now a leading approach to the goal of unifying general
relativity with quantum physics. Scientists using this theory to trace our
universe backward in time have found that its beginning point had a minimum
volume that is not zero and a maximum energy that is not infinite. As a
result of these limits, the theory's equations continue to produce valid
mathematical results past the point of the classical Big Bang, giving
scientists a window into the time before the Big Bounce.
Quantum-gravity theory indicates that the fabric of space-time has an
"atomic" geometry that is woven with one-dimensional quantum threads. This
fabric tears violently under the extreme conditions dominated by quantum
physics near the Big Bounce, causing gravity to become strongly repulsive so
that, instead of vanishing into infinity as predicted by Einstein's Theory
of General Relativity, the universe rebounded in the Big Bounce that gave
birth to our expanding universe. The theory reveals a contracting universe
before the Big Bounce, with space-time geometry that otherwise was similar
to that of our universe today.
Bojowald found he had to create a new mathematical model to use with the
theory of Loop Quantum Gravity in order to explore the universe before the
Big Bounce with more precision. "A more precise model was needed within Loop
Quantum Gravity than the existing numerical methods, which require
successive approximations of the solutions and yield results that are not as
general and complete as one would like," Bojowald explained. He developed a
mathematical model that produces precise analytical solutions by solving of
a set of mathematical equations.
In addition to being more precise, Bojowald's new model also is much
shorter. He reformulated the quantum-gravity models using a different
mathematical description, which he says made it possible to solve the
equations explicitly and also turned out to be a strong simplification. "The
earlier numerical model looked much more complicated, but its solutions
looked very clean, which was a clue that such a mathematical simplification
might exist," he said. Bojowald reformulated quantum gravity's differential
equations -- which require many calculations of numerous consecutive small
changes in time -- into an integrable system -- in which a cumulative length
of time can be specified for adding up all the small incremental changes.
The model's equations require parameters that describe the state of our
current universe accurately so that scientists then can use the model to
travel backward in time, mathematically "un-evolving" the universe to reveal
its state at earlier times. The model's equations also contain some "free"
parameters that are not yet known precisely but are nevertheless necessary
to describe certain properties. Bojowald discovered that two of these free
parameters are complementary: one is relevant almost exclusively after the
Big Bounce and the other is relevant almost exclusively before the Big
Bounce. Because one of these free parameters has essentially no influence on
calculations of our current universe, Bojowald colludes that it cannot be
used as a tool for back-calculating its value in the earlier universe before
the Big Bounce.
The two free parameters, which Bojowald found were complementary, represent
the quantum uncertainty in the total volume of the universe before and after
the Big Bang. "These uncertainties are additional parameters that apply when
you put a system into a quantum context such as a theory of quantum
gravity," Bojowald said. "It is similar to the uncertainty relations in
quantum physics, where there is complimentarity between the position of an
object and its velocity -- if you measure one you cannot simultaneously
measure the other." Similarly, Bojowald's study indicates that there is
complementarity between the uncertainty factors for the volume of the
universe before the Big Bounce and the universe after the Big Bounce. "For
all practical purposes, the precise uncertainty factor for the volume of the
previous universe never will be determined by a procedure of calculating
backwards from conditions in our present universe, even with most accurate
measurements we ever will be able to make," Bojowald explained. This
discovery implies further limitations for discovering whether the matter in
the universe before the Big Bang was dominated more strongly by quantum or
classical properties.
"A problem with the earlier numerical model is you don't see so clearly what
the free parameters really are and what their influence is," Bojowald said.
"This mathematical model gives you an improved expression that contains all
the free parameters and you can immediately see the influence of each one,"
he explained. "After the equations were solved, it was rather immediate to
reach conclusions from the results."
Bojowald reached an additional conclusion after finding that at least one of
the parameters of the previous universe did not survive its trip through the
Big Bounce -- that successive universes likely will not be perfect replicas
of each other. He said, "the eternal recurrence of absolutely identical
universes would seem to be prevented by the apparent existence of an
intrinsic cosmic forgetfulness."
Source: Penn State
____
Ken
"Buddhism elucidates why we are sentient."
"Buddhism follows thought throughout the Universe."
"Karma means that you don't get away with anything."
date: Sun, 1 Jul 2007 19:52:03 -0500
author: Ken Kubos
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