the Big Bounce is generic in LQC, say G.Date and G.Hossain(adsbygoogle = window.adsbygoogle || []).push({});

in a new paper http://arxiv.org/gr-qc/0407074 [Broken]

In LQC, as long as there is a scalar matter field, the bounce is

generic in the sense of being independent of

quantizing ambiguities and details of scalar field dynamics.

they also find that in a closed universe the Big Crunch singularity

goes away as well (in LQC) and is replaced generically by a bounce.

It looks to me like part of LQC coming of age---Bojowald got the

original result which zapped the Big Bang singularity and now more people

are joining in and corroborating and extending his result. these two

authors, as it happens, have found, or helped to find, a useful approximation of Bojo's original cosmological difference equation by a differential equation (see their equation 1) which looks nicer and neater than the difference equation especially in their choice of notation. More exactly, they have an "effective Hamiltonian" to approximate bojo's

original LQC Hamiltonian, and it looks as if they are milking that effective

Hamiltonian cow for all its worth. Both guys are of the smart young bunch of researchers that have gotten into Loop during the past few years

and right now they are in Chennai which looks like might become another center. So it is a "field maturation" paper, I think, as if people are finishing digging a tunnel thru the mountain and Bojo made a hole and saw some

sky thru it and other people help make the hole larger and after a while break out into the open daylight at the other end.

It is a short paper---the work looks good as far as I can tell. Here is an introductory paragraph exerpt

-----quote----

It has been long expected that the existence of singularity in the classical general relativity which has been shown to be quite generic thanks to the singularity theorems, will be removed when classical framework of gravity is extended to a quantum framework of gravity.

Despite of tremendous efforts made, unfortunately we still do not have a fully satisfactory theory of quantum gravity. In the las tcouple of decades two strong contenders have emerged: the string theory approach[1] and the loop quantum gravity (LQG) approach[2].

Theissueof fate of classical cosmological singularities has been addressed head-on within the LQG approach. More precisely, the adaptation of LQG methods to cosmological context, known as loop quantum cosmology (LQC) [3], has made impressive progress on the issue of singularities. It has been shown that the isotropic models (flat and closed)[4], and more generally the diagonal Bianchi class A models [5, 6], are free of singularity.

It is time now to explore further consequences of LQC corrected cosmologies.

---end quote---

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# Big Bounce generic, Date and Hossain

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