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The Beginning of Everything: A New Paradigm Shift for the Infant Universe

A new paradigm for understanding the earliest eras in the history of the universe has been developed by scientists at Penn State University. Using techniques from an area of modern physics called loop quantum cosmology, developed at Penn State, the scientists now have extended analyses that include quantum physics farther back in time than ever before -- all the way to the beginning. The new paradigm of loop quantum origins shows, for the first time, that the large-scale structures we now see in the universe evolved from fundamental fluctuations in the essential quantum nature of "space-time," which existed even at the very beginning of the universe over 14 billion years ago. The achievement also provides new opportunities for testing competing theories of modern cosmology against breakthrough observations expected from next-generation telescopes. The research will be published on 11 December 2012 as an "Editor's Suggestion" paper in the scientific journal Physical Review Letters.
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Blobrana


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Loop quantum gravity theory
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Galaxies could give glimpse of the instant time began

The structure of the universe at its very first instant - when time itself was still emerging - may be visible in the pattern of galaxies today. That's the latest prediction of a theory that fuses quantum mechanics and Einstein's general theory of relativity.
Relativity describes gravity as a curve in the geometry of space and time. This mostly works, but quails at the quantum scale of the very start of the big bang, when everything was infinitely dense.
Enter loop quantum gravity theory, which says space-time is underpinned by a network of loops in which no distance can be smaller than 10-35 metres, a unit known as the Planck length.
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Blobrana


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Title: In search of lost spacetime: philosophical issues arising in quantum gravity
Authors: Christian Wuthrich

This essay presents an accessible introduction to the basic motivations to seek a quantum theory of gravity. It focuses on one approach - loop quantum gravity - as an example of the rich philosophical issues that arise when we try to combine spacetime and quantum physics.

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Blobrana


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Abhay Ashtekar remembers his reaction the first time he saw the universe bounce.
He was watching a simulation of the universe rewind towards the big bang. Mostly the universe behaved as expected, becoming smaller and denser as the galaxies converged. But then, instead of reaching the big bang "singularity", the universe bounced and started expanding again. What on earth was happening?
Ashtekar wanted to be sure of what he was seeing, so he asked his colleagues to sit on the result for six months before publishing it in 2006. And no wonder. The theory that the recycled universe was based on, called loop quantum cosmology (LQC), had managed to illuminate the very birth of the universe - something even Einstein's general theory of relativity fails to do.

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Loop Quantum Gravity
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Title: Loop Quantum Gravity: An Inside View
Author: Thomas Thiemann

This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The present text can be viewed in part as a response to an article by Nicolai, Peeters and Zamaklar (hep-th/0501114). We also explain why certain no go conclusions drawn from a mathematically correct calculation in a recent paper by Helling et al (hep-th/0409182) are physically incorrect.

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Blobrana


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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. Beyond that point, we needed to apply quantum tools that were not available to Einstein" - Abhay Ashtekar, Holder of the Eberly Family Chair in Physics and Director of the Institute for Gravitational Physics and Geometry at Penn State.

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.

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Elements of Loop Quantum Cosmology:

The expansion of our universe, when followed backward in time, implies that it emerged from a phase of huge density, the big bang. These stages are so extreme that classical general relativity combined with matter theories is not able to describe them properly, and one has to refer to quantum gravity.
A complete quantization of gravity has not yet been developed, but there are many results about key properties to be expected. When applied to cosmology, a consistent picture of the early universe arises which is free of the classical pathologies and has implications for the generation of structure which are potentially observable in the near future.

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