Achour, Jibril Ben Brahma, Suddhasattwa Uzan, Jean-Philippe

This article proposes a generalization of the Oppenheimer-Snyder model which describes a bouncing compact object. The corrections responsible for the bounce are parameterized in a general way so as to remain agnostic about the specific mechanism of singularity resolution at play. It thus develops an effective theory based on a thin shell approach, ...

Boumaza, Hamza Langlois, David Noui, Karim

We study the late cosmological evolution, from the nonrelativistic matter dominated era to the dark energy era, in modified gravity models described by Degenerate Higher-Order Scalar-Tensor (DHOST) theories. They represent the most general scalar-tensor theories propagating a single scalar degree of freedom and include Horndeski and Beyond Horndesk...

Artigas, Danilo Crowe, Sean Mielczarek, Jakub

In the recent article Phys. Rev. D 100, no. 4, 043533 (2019) a compact phase space generalization of the flat de Sitter cosmology has been proposed. The main advantages of the compactification is that physical quantities are bounded, and the quantum theory is characterized by finite dimensional Hilbert space. Furthermore, by considering the $\mathb...

Ben Achour, Jibril Uzan, Jean-Philippe

This article presents an effective quantum extension of the seminal Oppenheimer-Snyder (OS) collapse in which the singularity resolution is modeled using the effective dynamics of the spatially closed loop quantum cosmology. Using the Israel-Darmois junction conditions, it shows that one can consistently glue this bouncing LQC geometry to the class...

Guimarey, Danilo Artigas Mielczarek, Jakub Rovelli, Carlo

The kinematical phase space of classical gravitational field is flat (affine) and unbounded. Because of this, field variables may tend to infinity leading to appearance of singularities, which plague Einstein's theory of gravity. The purpose of this article is to study the idea of generalizing the theory of gravity by compactification of the phase ...

Brax, Philippe Valageas, Patrick

We propose a simple model that provides a dynamical cancellation mechanism of the vacuum energy density appearing either in the form of a bare cosmological constant, quantum fluctuations of matter fields or the result of phase transitions. This `conformal compensator model' is based on a conformal coupling $A(\varphi)$ between the Einstein and the ...

Gorji, Mohammad Ali Mukohyama, Shinji Firouzjahi, Hassan

It is well known that the standard scalar field mimetic cosmology provides a dark matter-like energy density component. Considering $SU(2)$ gauge symmetry, we study the gauge field extension of the mimetic scenario in spatially flat and curved FLRW spacetimes. Because of the mimetic constraint, the standard Yang-Mills term plays the role of the cos...

Alesci, Emanuele Botta, Gioele Stagno, Gabriele V.

We introduce a new regularization scheme for Quantum Cosmology in Loop Quantum Gravity (LQG) using the tools of Quantum Reduced Loop Gravity (QRLG). It is obtained considering density matrices for superposition of graphs based on statistical countings of microstates compatible with macroscopic configurations. We call this procedure statistical regu...

Gannouji, Radouane Kazantzidis, Lavrentios Perivolaropoulos, Leandros Polarski, David

Recent analyses \cite{Nesseris:2017vor,Kazantzidis:2018rnb} have indicated that an effective Newton's constant $G_{\rm eff}(z)$ decreasing with redshift may relieve the observed tension between the Planck15 best fit $\Lambda$CDM cosmological background ({\it i.e.} Planck15/$\Lambda$CDM) and the corresponding $\Lambda$CDM background favored by growt...

Altamirano, Natacha Pascalie, Romain Mann, Robert B.
Published in
General Relativity and Gravitation

Motivated by the recent increased interest in energy non-conserving models in cosmology, we extend the analysis of the cosmological consequences of the Classical Channel Model of Gravity (CCG). This model is based on the classicalâ€“quantum interaction between a test particle and a metric (classical) and results in a theory with a modified Wheelerâ€“de...