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...

Damour, Thibault Vilenkin, Alexander

An oscillating, compact FLRW universe with a massive conformally coupled scalar field is studied in the framework of quantum cosmology. The scalar field is treated as a perturbation and we look for solutions of the Wheeler-DeWitt equation describing stable stationary states of the model. We assume that the previous sources of quantum instability th...

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 ...

Fanizza, Giuseppe Gasperini, Maurizio Marozzi, Giovanni Veneziano, Gabriele

We show that the angular directions locally measured by a static geodesic observer in a generic cosmological background and expressed in the system of Fermi Normal Coordinates always coincide with those expressed in the Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits the residual gauge freedom of the GLC coordinates. Th...

Pattison, Chris Vennin, Vincent Assadullahi, Hooshyar Wands, David

We study the stochastic formalism of inflation beyond the usual slow-roll approximation. We verify that the assumptions on which the stochastic formalism relies still hold even far from the slow-roll attractor. This includes demonstrating the validity of the separate universe approach to evolving long-wavelength scalar field perturbations beyond sl...

Peter, Patrick

Quantum cosmology based on the Wheeler De Witt equation represents a simple way to implement plausible quantum effects in a gravitational setup. In its minisuperspace version wherein one restricts attention to FLRW metrics with a single scale factor and only a few degrees of freedom describing matter, one can obtain exact solutions and thus acquire...

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 [S. Nesseris et al., Phys. Rev. D 96, 023543 (2017)PRVDAQ2470-001010.1103/PhysRevD.96.023543; L. Kazantzidis and L. Pervolaropoulos, Phys. Rev. D 97, 103503 (2018)PRVDAQ2470-001010.1103/PhysRevD.97.103503] have indicated that an effective Newton’s constant Geff(z) decreasing with redshift may relieve the observed tension between the...

Bahamonde, Sebastian Böhmer, Christian G. Carloni, Sante Copeland, Edmund J. Fang, Wei Tamanini, Nicola

The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our Universe put into sharp focus the need of a consistent theoretical model to explain the origin of this acceleration. As a result over the past two decades there has been a huge theoretical and observational effort into improving our understanding of the Universe. The c...

Cusin, Giulia Pitrou, Cyril Uzan, Jean-Philippe

Unresolved sources of gravitational waves are at the origin of a stochastic gravitational wave background. While the computation of its mean density as a function of frequency in a homogeneous and isotropic universe is standard lore, the computation of its anisotropies requires understanding the coarse graining from local systems, to galactic scale...