Results 51 to 60 of about 11,605 (193)
, 2011 We deduce general expressions for the line element of universe models with negative and vanishing spatial curvature described by conformally flat spacetime coordinates.
E. Eriksen +8 more
core +1 more source
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 +3 more
doaj +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 +4 more
openaire +1 more source
Electronic Journal of Qualitative Theory of Differential EquationsIn this paper, we consider the radially symmetric spacelike solutions of a nonlinear Dirichlet problem for the prescribed mean curvature spacelike equation in a Friedmann–Lemaître–Robertson–Walker spacetime.
Ting Wang, Man Xu
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. +2 more
openaire +4 more sources
(N+1)-dimensional Lorentzian evolving wormholes supported by polytropic matter
, 2013 In this paper we study $(N+1)$-dimensional evolving wormholes supported by energy satisfying a polytropic equation of state. The considered evolving wormhole models are described by a constant redshift function and generalizes the standard flat Friedmann-
Arostica, Fernanda +2 more
core +1 more source
Limits to Global Rotation and Shear From the COBE DMR 4-Year Sky Maps [PDF]
, 1997 Small departures from a homogeneous isotropic spacetime create observable features in the large-scale anisotropy of the cosmic microwave background. We cross-correlate the maps of the cosmic microwave background anisotropy from the Cosmic Background ...
Banday, A. J., Hinshaw, G., Kogut, A.
core +2 more sources
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
Wormhole Cosmology and the Horizon Problem
, 1992 We construct an explicit class of dynamic lorentzian wormholes connecting Friedmann-Robertson-Walker (FRW) spacetimes. These wormholes can allow two-way transmission of signals between spatially separated regions of spacetime and could permit such ...
A. Albrecht +20 more
core +1 more source
Fortschritte der Physik, Volume 74, Issue 4, April 2026.Abstract String theory has strong implications for cosmology, implying the absence of a cosmological constant, ruling out single‐field slow‐roll inflation, and that black holes decay. The origins of these statements are elucidated within the string‐theoretical swampland programme.
Kay Lehnert
wiley +1 more source