Does the big rip happen in LQC?

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Discussion Overview

The discussion revolves around the possibility of a "big rip" occurring within the framework of Loop Quantum Cosmology (LQC). Participants explore the implications of LQC on singularities, particularly in relation to dark energy models and the behavior of the universe at extreme conditions, such as during the big bang and potential future singularities.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants argue that LQC does not predict a big rip, suggesting that LQC's gravity-induced corrections at high densities could prevent such singularities.
  • Others assert that a big rip can occur under certain conditions, particularly with phantom-like equations of state, which could lead to future singularities.
  • There are speculations about LQC potentially resolving various singularities, including the big bang and big rip, through similar mechanisms.
  • One participant raises the concern that multiple bounces in LQC models may lead to increasing inhomogeneities, questioning the stability of such a scenario.
  • Another participant discusses the role of high-temperature radiation before a big rip, suggesting it could counteract the conditions necessary for a big rip to occur.
  • There is a debate about the number of bounces in LQC models, with some asserting that a common model has only one bounce, while others propose a cyclic model with multiple bounces.
  • Clarifications are sought regarding the interpretation of a paper by Param Singh, with participants discussing whether it supports the occurrence of a bounce during a big rip.

Areas of Agreement / Disagreement

Participants express differing views on whether a big rip can occur in LQC, with some asserting it is not a generic feature while others suggest it could happen under specific conditions. The discussion remains unresolved regarding the implications of LQC on singularities and the nature of bounces.

Contextual Notes

Limitations include the dependence on specific models and assumptions about dark energy and equations of state. The discussion highlights the complexity of singularity resolution in LQC and the need for further exploration of these concepts.

  • #31
Hmm, right on spot. Although this paper was not related to my question, it was what made me free associate with my question.

BTW, why Marcus is ignoring me? :(
 
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  • #32
Look at what I found:

http://arxiv.org/abs/0907.5591v3

Non-singular Ekpyrotic/Cyclic model in Loop Quantum Cosmology
Authors: Thomas Cailleteau, Parampreet Singh, Kevin Vandersloot
(Submitted on 31 Jul 2009 (v1), last revised 23 Oct 2009 (this version, v3))

Abstract: We study the role of non-perturbative quantum gravity effects in the Ekpyrotic/Cyclic model using the effective framework of loop quantum cosmology in the presence of anisotropies. We show that quantum geometric modifications to the dynamical equations near the Planck scale as understood in the quantization of Bianchi-I spacetime in loop quantum cosmology lead to the resolution of classical singularity and result in a non-singular transition of the universe from the contracting to the expanding branch. In the Planck regime, the universe undergoes multiple small bounces and the anisotropic shear remains bounded throughout the evolution. A novel feature, which is absent for isotropic models, is a natural turn around of the moduli field from the negative region of the potential leading to a cyclic phenomena as envisioned in the original paradigm. Our work suggests that incorporation of quantum gravitational effects in the Ekpyrotic/Cyclic model may lead to a viable scenario without any violation of the null energy condition.
 

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