Revisiting cosmological diffusion models in Unimodular Gravity and the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e4266" altimg="si54.svg"><mml:msub><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:math> tension

Cedeño, Francisco X. Linares; Nucamendi, Ulises

doi:10.1016/j.dark.2021.100807

Cited by 29 publications

(22 citation statements)

References 167 publications

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“…epoch, the CSL rate parameter is essentially the same as the non-relativistic version of the CSL model. This is a desirable feature to be included in our model because all results and observational bounds, regarding the CSL model, obtained from contemplating this cosmic stage, remain intact [89,90,111].…”

Section: The Collapse Rate Parametermentioning

confidence: 99%

“…The debate on the particular details involved in implementing the CSL model in the cosmological context is still open, and contains an extensive landscape of possibilities constituting an active research area at the moment [79][80][81][82][83][84]. As was already pointed out in [85], objective collapse models have the appealing feature of connecting plausible resolutions of other open problems in a single unified picture; not only the measurement problem in Quantum Mechanics and the emergence of the primordial inhomogeneities during inflation, but also the problem of time in canonical quantum theories of gravitation, the black hole information paradox [86][87][88] and other applications to cosmology, for instance to account for the dark energy and the late-time accelerated expansion of the universe [77,89,90].…”

Section: Introductionmentioning

confidence: 99%

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Enlightening the CSL model landscape in inflation

León

Bengochea

2021

Eur. Phys. J. C

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We propose a novel realization for the natural extrapolation of the continuous spontaneous localization (CSL) model, in order to account for the origin of primordial inhomogeneities during inflation. This particular model is based on three main elements: (i) the semiclassical gravity framework, (ii) a collapse-generating operator associated to a relativistic invariant scalar of the energy-momentum tensor, and (iii) an extension of the CSL parameter(s) as a function of the spacetime curvature. Furthermore, employing standard cosmological perturbation theory at linear order, and for a reasonable range within the parameter space of the model, we obtain a nearly scale invariant power spectrum consistent with recent observational CMB data. This opens a vast landscape of different options for the application of the CSL model to the cosmological context, and possibly sheds light on searches for a full covariant version of the CSL theory.

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Section: The Collapse Rate Parametermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enlightening the CSL model landscape in inflation

León

Bengochea

2021

Eur. Phys. J. C

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“…Unimodular Gravity (UG) is an alternative approach to GR that can be derived from the Einstein-Hilbert action by restricting to variations preserving the volume element [46][47][48][49][50][51]; hence, UG has less symmetries than GR. While the implementation of UG into the cosmological context, and its connection with the CC, has been noted for decades [15,[50][51][52][53], recently it has been rediscovered, gaining significant attention [54][55][56][57][58][59][60][61][62][63][64].…”

Section: Introductionmentioning

confidence: 99%

Inflation and the cosmological (not-so) constant in unimodular gravity

Leon

2022

Preprint

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We propose a mechanism for generating an inflationary phase in the early universe without resorting to any type of scalar field(s). Instead, this accelerated expansion is driven by a dynamical "cosmological constant" in the framework of unimodular gravity. The time dependent cosmological constant can be related to an energy diffusion term that arises naturally in unimodular gravity due to its restrictive diffeomorphism invariance. We derive the generic conditions required for any type of diffusion to generate a realistic inflationary epoch. Furthermore, for a given parameterization of inflation (in terms of the Hubble flow functions), we show how to construct the corresponding diffusion term in such a way that a smooth transition occurs between inflation and the subsequent radiation dominated era, hence reheating proceeds naturally. The primordial spectrum is obtained during the inflationary phase by considering inhomogeneous perturbations associated to standard hydrodynamical matter (modeled as a single ultra-relativistic fluid). We demonstrate that the resulting spectrum is equivalent to that obtained in traditional inflationary models, and is also independent of the particular form of the diffusion term. In addition, we analyze the feasibility of identifying the variable cosmological constant, responsible for the inflationary expansion, with the current observed value.

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“…The debate on the particular details involved in implementing the CSL theory in the cosmological context is still open, and contains an extensive landscape of possibilities constituting a active research area at the moment [79][80][81][82][83][84]. As was already pointed out in [85], objective collapse models have the appealing feature of connecting plausible resolutions of other open problems in a single unified picture; not only the measurement problem in Quantum Mechanics and the emergence of the primordial inhomogeneities during inflation, but also the problem of time in canonical quantum theories of gravitation, the black hole information paradox [86][87][88] and other applications to cosmology, for instance to account for the dark energy and the late-time accelerated expansion of the universe [77,89,90].…”

Section: Introductionmentioning

confidence: 99%

Enlightening the CSL model landscape in inflation

León,

Bengochea

2021

Preprint

View full text Add to dashboard Cite

We propose a novel model for the natural extrapolation of the continuous spontaneous localization (CSL) theory, in order to account for the origin of primordial inhomogeneities during inflation. This particular model is based on three main elements: (i) the semiclassical gravity framework, (ii) a collapse-generating operator associated to a relativistic invariant scalar of the energy-momentum tensor, and (iii) an extension of the CSL parameter(s) as a function of the spacetime curvature. Furthermore, employing standard cosmological perturbation theory at linear order, and for a reasonable range within the parameter space of the model, we obtain a nearly scale invariant power spectrum consistent with recent observational CMB data. This opens a vast landscape of different options for the application of the CSL theory to the cosmological context, and possibly sheds light on searches for a full covariant version of the CSL theory.

show abstract

Revisiting cosmological diffusion models in Unimodular Gravity and the H0 tension

Cited by 29 publications

References 167 publications

Enlightening the CSL model landscape in inflation

Enlightening the CSL model landscape in inflation

Inflation and the cosmological (not-so) constant in unimodular gravity

Enlightening the CSL model landscape in inflation

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