Classical bounce: Constraints and consequences

Falciano, F. T.; Lilley, M.; Peter, Patrick

doi:10.1103/physrevd.77.083513

Cited by 57 publications

(73 citation statements)

References 59 publications

(103 reference statements)

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“…• How do those results compare with models dealing with classical bounces (see, e.g., [23])? If the IR power suppression is probably a generic feature of bounces, the detailed features are modeldependent.…”

Section: Discussionmentioning

confidence: 99%

Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves

et al. 2010

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Loop quantum cosmology provides an efficient framework to study the evolution of the Universe beyond the classical Big Bang paradigm. Because of holonomy corrections, the singularity is replaced by a "bounce." The dynamics of the background is investigated into the details, as a function of the parameters of the model. In particular, the conditions required for inflation to occur are carefully considered and are shown to be generically met. The propagation of gravitational waves is then investigated in this framework. By both numerical and analytical approaches, the primordial tensor power spectrum is computed for a wide range of parameters. Several interesting features could be observationally probed.

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Section: Discussionmentioning

confidence: 99%

Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves

et al. 2010

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“…A generic consequence of violating the null energy condition is the appearance of fields with negative kinetic energy: ghosts; a crucial point in bouncing models is actually to construct a regular model in which such ghosts are absent while still having a bouncing phase. It is possible to generate a bounce in the presence of curvature K = 1 without violating the NEC, but only the strong energy condition, SEC, which demands ρ + P ≥ 0 and ρ + 3P ≥ 0, see [22,49] for concrete models. Such a bounce could leave some amount of spatial curvature in the expanding phase, whose amplitude may require a subsequent inflationary phase to dilute it, hence possibly ruining the alternative-to-inflation program (as emphasized above, we shall not be concerned here with the mixed models in which a bounce permits to avoid a primordial singularity while a subsequent inflation phase solves the other puzzles of the standard hot big-bang model).…”

Section: B What Is Used To Get a Bounce?mentioning

confidence: 99%

“…How spatial curvature can drastically modify a model's prediction is illustrated in [22,49]: here, a simple bouncing model is considered, based on a scalar field and curvature. The former has a potential whose maximum is reached at the bounce, which is canceled by the curvature contribution, such that H → 0 without violating the NEC.…”

Section: Spatial Curvature and Non-gaussianitiesmentioning

confidence: 99%

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A critical review of classical bouncing cosmologies

2015

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Given the proliferation of bouncing models in recent years, we gather and critically assess these proposals in a comprehensive review. The PLANCK data shows an unmistakably red, quasi scaleinvariant, purely adiabatic primordial power spectrum and no primary non-Gaussianities. While these observations are consistent with inflationary predictions, bouncing cosmologies aspire to provide an alternative framework to explain them. Such models face many problems, both of the purely theoretical kind, such as the necessity of violating the NEC and instabilities, and at the cosmological application level, as exemplified by the possible presence of shear. We provide a pedagogical introduction to these problems and also assess the fitness of different proposals with respect to the data. For example, many models predict a slightly blue spectrum and must be fine-tuned to generate a red spectral index; as a side effect, large non-Gaussianities often result.We highlight several promising attempts to violate the NEC without introducing dangerous instabilities at the classical and/or quantum level. If primordial gravitational waves are observed, certain bouncing cosmologies, such as the cyclic scenario, are in trouble, while others remain valid. We conclude that, while most bouncing cosmologies are far from providing an alternative to the inflationary paradigm, a handful of interesting proposals have surfaced, which warrant further research. The constraints and lessons learned as laid out in this review might guide future research.

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“…This model might be interesting in its own right, and further details will be presented elsewhere. For previous work on bouncing solutions and their likelihood see, for example, [59,60]. …”

Section: Bounce Solutionmentioning

confidence: 99%

Anisotropic, nonsingular early universe model leading to a realistic cosmology

2009

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We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a non-singular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'Big Bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the Big Bang. We demonstrate that there exist geodesics extending through the Big Bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the Big Bang, rendering it, at worst, a quasi-regular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasi-regular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropisation and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [1,2,3]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalises the known bouncing solution in closed FRW universes.

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Classical bounce: Constraints and consequences

Cited by 57 publications

References 59 publications

Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves

Inflation in loop quantum cosmology: Dynamics and spectrum of gravitational waves

A critical review of classical bouncing cosmologies

Anisotropic, nonsingular early universe model leading to a realistic cosmology

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