Results 61 to 70 of about 6,154 (134)

Physical basis for the symmetries in the Friedmann–Robertson–Walker metric [PDF]

, 2016
Modern cosmological theory is based on the Friedmann–Robertson–Walker (FRW) metric. Often written in terms of co-moving coordinates, this well-known solution to Einstein’s equations owes its elegant and highly practical formulation to the cosmological ...
F. Melia
semanticscholar   +1 more source

Reply to “Comment on ‘Quantization of Friedmann-Robertson-Walker spacetimes in the presence of a negative cosmological constant and radiation”’ [PDF]

Physical Review D, 2007
The previous Comment contains a valid criticism of the numerical precision of the results reported in a recent paper of ours, as well as fresh ideas on how to characterize a quantum cosmological singularity. However, we argue that, contrary to what is suggested in the Comment, the quantum cosmological models we studied show hardly any sign of singular ...
N. A. Lemos, G. A. Monerat, E. V. Corrêa Silva, G. Oliveira-Neto, L. G. Ferreira Filho   +4 more
openaire   +1 more source

Quantum Brownian motion in an analog Friedmann-Robertson-Walker geometry [PDF]

, 2017
In this paper we study the effects of quantum scalar field vacuum fluctuations on scalar test particles in an analog model for the Friedmann-Robertson-Walker spatially flat geometry. In this scenario, the cases with one and two perfectly reflecting plane
C. Bessa, V. B. Bezerra, E. B. de Mello, H. Mota   +3 more
semanticscholar   +1 more source

Anisotropic solutions in symmetric teleparallel $$f\left( Q\right) $$ f Q -theory: Kantowski–Sachs and Bianchi III LRS cosmologies

European Physical Journal C: Particles and Fields, 2023
We investigate the existence of anisotropic self-similar exact solutions in symmetric teleparallel $$f\left( Q\right) $$ f Q -theory. For the background geometry we consider the Kantowski–Sachs and the Locally Rotationally Symmetric Bianchi type III ...
N. Dimakis, M. Roumeliotis, A. Paliathanasis, T. Christodoulakis   +3 more
doaj   +1 more source

A fully covariant information-theoretic ultraviolet cutoff for scalar fields in expanding Friedmann Robertson Walker spacetimes [PDF]

Journal of Mathematical Physics, 2013
While a natural ultraviolet cutoff, presumably at the Planck length, is widely assumed to exist in nature, it is nontrivial to implement a minimum length scale covariantly. This is because the presence of a fixed minimum length needs to be reconciled with the ability of Lorentz transformations to contract lengths.
Kempf, A., Chatwin-Davies, A., Martin, R. T. W.   +2 more
openaire   +4 more sources

Friedmann–Robertson–Walker models do not require zero active mass [PDF]

, 2016
The $R_h = ct$ cosmological model has received considerable attention in recent years owing to claims that it is favoured over the standard $\Lambda$ cold dark matter ($\Lambda$CDM) model by most observational data.
Do Young Kim, A. Lasenby, M. Hobson
semanticscholar   +1 more source

Existence of Solutions of Semilinear Wave Equations With Time‐Dependent Propagation Speed and Time Derivative Nonlinearity

Mathematical Methods in the Applied Sciences, Volume 49, Issue 9, Page 8681-8690, June 2026.
ABSTRACT Consider wave equations with time derivative nonlinearity and time‐dependent propagation speed which are generalized versions of the wave equations in the Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime, the de Sitter spacetime and the anti‐de Sitter space time.
Kimitoshi Tsutaya, Yuta Wakasugi
wiley   +1 more source

The imprint of primordial gravitational waves on the CMB intensity profile

Physics Letters B, 2021
We use the induced geometry on the two dimensional transverse cross section of a photon beam propagating on a perturbed Friedmann-Robertson-Walker (FRW) spacetime to find the Cosmic Microwave Background (CMB) photon distribution over a telescope's ...
Ali Kaya
doaj   +1 more source

Background Instability of Quintessence Model in Light of Entropy and Distance Conjecture

Fortschritte der Physik, Volume 74, Issue 6, June 2026.
ABSTRACT We apply the covariant entropy bound argument supporting the de Sitter swampland conjecture to the quintessence model, to find out the condition for the background to be unstable. More concretely, the background is unstable when the matter entropy given by the species number of the effective field theory increases more rapidly than the ...
Min‐Seok Seo
wiley   +1 more source

Could a thin-shell configuration lie hidden within the universe?

European Physical Journal C: Particles and Fields
This article explores the cosmological scenario in which our Universe contains a hidden thin-shell configuration. We investigate a degenerate modification of the Friedmann-Robertson-Walker metric obtained through a coordinate transformation applied to ...
Mauricio Cataldo, Antonella Cid, Pedro Labraña   +2 more
doaj   +1 more source