Astrophysics, abstract
astro-ph/0602515
From: Eckhard Rebhan [view email]
Date: Thu, 23 Feb 2006 14:28:35 GMT (63kb)
"Soft bang" instead of "big bang": model of an inflationary universe without singularities and with eternal physical past time
Authors: E. Rebhan (Heinrich-Heine-Universitaet Duesseldorf)
Comments: 21 pages, 5 figures
Journal-ref: Astron. Astrophys. 353, 1-9 (2000)
The solution for an inflationary universe without singularities is derived from the Einstein-Lemaitre equations. The present state of the universe evolved from a steady state solution for a tiny, but classical micro-universe with large cosmological constant or large equivalent vacuum energy density and with an equal energy density of radiation and/or some kind of relativistic primordial matter in the infinite past. An instability of this state outside the quantum regime caused a "soft bang" by triggering an expansion that smoothly started with zero expansion rate, continuously increased, culminated in an exponentially inflating phase and ended through a phase transition, the further evolution being a Friedmann-Lemaitre evolution as in big bang models. As a necessary implication of the model the universe must be closed. All other parameters of the model are very similar to those of big bang models and comply with observational constraints.
http://arxiv.org/abs/astro-ph/0602515General Relativity and Quantum Cosmology, abstract
gr-qc/0602086
From: Parampreet Singh [view email]
Date: Wed, 22 Feb 2006 20:22:34 GMT (552kb)
Quantum Nature of the Big Bang
Authors: Abhay Ashtekar, Tomasz Pawlowski, Parampreet Singh
Comments: Revtex4, 4 Pages, 2 Figures
Report-no: IGPG 06/2-1
Some long standing issues concerning the quantum nature of the big bang are resolved in the context of homogeneous isotropic models with a scalar field. Specifically, the known results on the resolution of the big bang singularity in loop quantum gravity are significantly extended as follows: i) the scalar field is shown to serve as an internal clock, thereby providing a detailed realization of the `emergent time' idea; ii) the physical Hilbert space, Dirac observables and semi-classical states are constructed rigorously; iii) the Hamiltonian constraint is solved numerically to show that the big bang is replaced by a big bounce. Thanks to the non-perturbative, background independent methods, unlike in other approaches the quantum evolution is deterministic across the deep Planck regime.
http://arxiv.org/abs/gr-qc/0602086