Penn State Researchers Look Beyond the Birth of the Universe (Forwarded)

Office of Public Information
Eberly College of Science
Penn State
University Park, Pennsylvania

SCIENCE CONTACTS:
Abhay Ashtekar (by phone after 1 June), (+1)814-863-9601
Tomasz Pawlowski (by phone before 1 June), (+1)865-2924
Parmpreet Singh (by phone before 1 June), (+1)865-2924

PIO CONTACT:
Barbara Kennedy, (+1)814-863-4682

12 May 2006

Penn State Researchers Look Beyond the Birth of the Universe

According to Einstein's general theory of relativity, the Big Bang
represents The Beginning, the grand event at which not only matter but
space-time itself was born. While classical theories offer no clues
about existence before that moment, a research team at Penn State has
used quantum gravitational calculations to find threads that lead to an
earlier time. "General relativity can be used to describe the universe
back to a point at which matter becomes so dense that its equations
don't hold up," says Abhay Ashtekar, Holder of the Eberly Family Chair
in Physics and Director of the Institute for Gravitational Physics and
Geometry at Penn State. "Beyond that point, we needed to apply quantum
tools that were not available to Einstein." By combining quantum physics
with general relativity, Ashtekar and two of his post-doctoral
researchers, Tomasz Pawlowski and Parmpreet Singh, were able to develop
a model that traces through the Big Bang to a shrinking universe that
exhibits physics similar to ours.

In research reported in the current issue of Physical Review Letters,
the team shows that, prior to the Big Bang, there was a contracting
universe with space-time geometry that otherwise is similar to that of
our current expanding universe. As gravitational forces pulled this
previous universe inward, it reached a point at which the quantum
properties of space-time cause gravity to become repulsive, rather than
attractive. "Using quantum modifications of Einstein's cosmological
equations, we have shown that in place of a classical Big Bang there is
in fact a quantum Bounce," says Ashtekar. "We were so surprised by the
finding that there is another classical, pre-Big Bang universe that we
repeated the simulations with different parameter values over several
months, but we found that the Big Bounce scenario is robust."

While the general idea of another universe existing prior to the Big
Bang has been proposed before, this is the first mathematical
description that systematically establishes its existence and deduces
properties of space-time geometry in that universe.

The research team used loop quantum gravity, a leading approach to the
problem of the unification of general relativity with quantum physics,
which also was pioneered at the Penn State Institute of Gravitational
Physics and Geometry. In this theory, space-time geometry itself has a
discrete 'atomic' structure and the familiar continuum is only an
approximation. The fabric of space is literally woven by one-dimensional
quantum threads. Near the Big-Bang, this fabric is violently torn and
the quantum nature of geometry becomes important. It makes gravity
strongly repulsive, giving rise to the Big Bounce.

"Our initial work assumes a homogenous model of our universe," says
Ashtekar. "However, it has given us confidence in the underlying ideas
of loop quantum gravity. We will continue to refine the model to better
portray the universe as we know it and to better understand the features
of quantum gravity."

The research was sponsored by the National Science Foundation, the
Alexander von Humboldt Foundation, and the Penn State Eberly College of
Science.

IMAGE CAPTION:
[http://www.science.psu.edu/alert/ima...ekarFigure.jpg (27KB)]
The figure represents our expanding universe as the right branch of the
arc. Our time now is located at the 1.8 grid mark on the right side of
the drawing. According to Ashtekar's team's calculations, when looking
backward throughout the history of the universe, 'time' does not go to
the point of the Big Bang but bounces to the left branch of the drawing,
which describes a contracting universe. Singh explains, "The state of
the universe depicted by its wavefunction is shown in space (mu) and
time(phi). The big bang singularity lies where space vanishes (goes to
zero). Our expanding phase of the universe is shown by the right branch
which, when reversed backward in time, bounces near the Big Bang to a
contracting phase (left branch) and never reaches the Big Bang."