The causal interpretation of dust and radiation fluid non-singular quantum cosmologies

Barros, J. Acácio de; Pinto-Neto, Nelson; Sagioro-Leal, M. A.

doi:10.1016/s0375-9601(98)00169-8

Cited by 170 publications

(149 citation statements)

References 9 publications

Supporting

Mentioning

143

Contrasting

Unclassified

Order By: Relevance

“…A proposal to circumvent this problem consists of assuming a trajectory formulation of quantum mechanics [114,115] in which the scale factor follows specific trajectory values [116]. Applying this formalism and assuming regular boundary conditions, one finds that all possible trajectories are nonsingular and include a bounce [117] (see also [118] for a different but related approach). Of course, all known formulations of quantum mechanics being strictly equivalent, the fact that the universe underwent a regular bouncing phase or not should not depend on which formulation one picks, so it is reasonable to expect that the results obtained in Refs.…”

Section: Canonical Quantum Cosmologymentioning

confidence: 99%

“…Such an approach is usually unfeasible unless an additional mini-superspace approximation is performed, in which the infinite number of degrees of freedom is reduced to a few, for instance by considering only homogeneous and isotropic metrics. In [117], it was shown that in the presence of a simple perfect fluid, the singularity can always be avoided, independent of the fluid's equation of state and the spatial curvature. Moreover, perturbations in such models can be treated self-consistently.…”

Section: Modified Gravitymentioning

confidence: 99%

See 1 more Smart Citation

A critical review of classical bouncing cosmologies

2015

View full text Add to dashboard Cite

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.

show abstract

Section: Canonical Quantum Cosmologymentioning

confidence: 99%

Section: Modified Gravitymentioning

confidence: 99%

A critical review of classical bouncing cosmologies

2015

View full text Add to dashboard Cite

show abstract

“…Bouncing cosmological models, [1][2][3][4][5][6] which solve the singularity problem, can also be considered as possible alternatives to inflation, as long as they are able to solve the horizon and flatness problems, and justify the observed power spectrum of primordial cosmological perturbations.…”

Section: Introductionmentioning

confidence: 99%

Bouncing Models With a Cosmological Constant

Pinto-Neto

Siffert

Maier

et al. 2011

Int. J. Mod. Phys. Conf. Ser.

View full text Add to dashboard Cite

Most bouncing models contain a contracting phase from a very large and rarefied state, where dark energy might have had an important role. If this is that case, the presence of dark energy can modify the initial conditions and evolution of cosmological perturbations, changing the known results already obtained in the literature concerning their amplitude and spectrum. In this work, we assume the simplest and most appealing candidate for dark energy, the cosmological constant, and study its influence on the evolution of cosmological perturbations during the contracting phase of a bouncing model, containing also a perfect fluid with constant equation of state parameter w. We show that, due to the vacuum state choice we have to make when a cosmological constant is present, the spectrum of the perturbations are substantially altered. We conclude that, in this case, the presence of a stiff matter fluid in the contracting phase is needed in order to have a scale invariant spectrum of perturbations in the expanding phase.

show abstract

“…A bouncing phase may originate from quantum gravity [7] or quantum cosmology [8], and have been seen to occur in some string-motivated models [9]. In one such model, based on the brane hypothesis in a five dimensional context, namely the ekpyrotic scenario [10], [11], the bounce in fact does not address the singularity problem since it is assumed to be singular.…”

Section: Introductionmentioning

confidence: 99%

Propagation of adiabatic and entropy perturbations in a bouncing universe

Peter

Pinto-Neto

Gonzalez

2003

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

By studying some bouncing universe models dominated by a specific class of hydrodynamical fluids, we show that the primordial cosmological perturbations may propagate smoothly through a general relativistic bounce. We also find that the purely adiabatic modes, although almost always fruitfully investigated in all other contexts in cosmology, are meaningless in the bounce or null energy condition (NEC) violation cases since the entropy modes can never be neglected in these situations: the adiabatic modes exhibit a fake divergence that is compensated in the total Bardeen gravitational potential by inclusion of the entropy perturbations.

show abstract

The causal interpretation of dust and radiation fluid non-singular quantum cosmologies

Cited by 170 publications

References 9 publications

A critical review of classical bouncing cosmologies

A critical review of classical bouncing cosmologies

Bouncing Models With a Cosmological Constant

Propagation of adiabatic and entropy perturbations in a bouncing universe

Contact Info

Product

Resources

About