Results 31 to 40 of about 51,631 (191)

Complex Riemannian Spacetime and Singularity-Free Black Holes and Cosmology

Axioms
An approach is presented to address singularities in general relativity using a complex Riemannian spacetime extension. We demonstrate how this method can be applied to both black hole and cosmological singularities, specifically focusing on the ...
John W. Moffat
doaj   +1 more source

Effective f(R) Actions for Modified Loop Quantum Cosmologies via Order Reduction

Universe, 2023
General Relativity is an extremely successful theory, at least for weak gravitational fields; however, it breaks down at very high energies, such as in correspondence to the initial singularity.
Ana Rita Ribeiro, Daniele Vernieri, Francisco S. N. Lobo   +2 more
doaj   +1 more source

Minisuperspace Examples of Quantization Using Canonical Variables of the Ashtekar Type: Structure and Solutions

, 1995
The Ashtekar variables have been use to find a number of exact solutions in quantum gravity and quantum cosmology. We investigate the origin of these solutions in the context of a number of canonical transformations (both complex and real) of the basic ...
A. Ashtekar, A. Lafiti, A. Taub, C. Misner, H. Kodama, H. Kodama, I. E. Segal, J. F. Barbero, J. Fernando Barbero, J. Hartle, K. Kuchař, M. Ryan, Michael P. Ryan, O. Obregon, P. D'Eath, R. Graham, V. Bargmann, V. Belinskii, V. Moncrief   +18 more
core   +1 more source

Aspects of Quantum Theory in General Relativity and Cosmology

, 2020
After a brief introduction to Cosmology some quantum aspects of General Relativity and cosmology are presented. The radial motion of a massive particles in the ergosphere of the Kerr Black Hole is considered. Screening of Hawking radiation and shielding of the Penrose process is examined in the context of the region of negative energy inside the ...
openaire   +2 more sources

Group Field Theory and Its Cosmology in a Matter Reference Frame

Universe, 2018
While the equations of general relativity take the same form in any coordinate system, choosing a suitable set of coordinates is essential in any practical application.
Steffen Gielen
doaj   +1 more source

Tests of standard cosmology in Hořava gravity, Bayesian evidence for a closed universe, and the Hubble tension

European Physical Journal C: Particles and Fields, 2022
We consider some background tests of standard cosmology in the context of Hořava gravity with different scaling dimensions for space and time, which has been proposed as a renormalizable, higher-derivative, Lorentz-violating quantum gravity model without
Nils A. Nilsson, Mu-In Park
doaj   +1 more source

Simple quantum cosmology: Vacuum energy and initial state

, 2005
A static non-singular 10-dimensional closed Friedmann universe of Planck size, filled with a perfect fluid with an equation of state with w = -2/3, can arise spontaneously by a quantum fluctuation from nothing in 11-dimensional spacetime.
D. Spergel, D. Youm, E. Elbaz, M. Novello, M. Tegmark, S. Alexander, S. Eidelman, T. R. Mongan, T.R. Mongan   +8 more
core   +2 more sources

Singularity: Raychaudhuri Equation once again [PDF]

, 2007
I first recount Raychaudhuri's deep involvement with the singularity problem in general relativity. I then argue that precisely the same situation has arisen today in loop quantum cosmology as obtained when Raychaudhuri discovered his celebrated equation.
A. A. Penzias, A. Ashtekar, A. Ashtekar, A. Ashtekar, A. K. Raychaudhuri, A. K. Raychaudhuri, A. K. Raychaudhuri, A. K. Raychaudhuri, A. K. Raychaudhuri, A. K. Raychaudhuri, E. Bianchi, E. Livine, E. Ruiz, J. M. M. Senovilla, J. M. M. Senovilla, M. Bojowald, N. Dadhich, N. Dadhich, N. Dadhich, Naresh Dadhich, S. Tsujikawa, S. W. Hawking, T. Padmanabhan   +22 more
core   +3 more sources

Non-metricity signatures on the Higgs boson signal strengths at the LHC

Journal of High Energy Physics, 2022
In this work we study the high-energy Higgs boson phenomenology associated to the non-metricity scale Λ Q at the LHC. Non-metricity is present in more generic non-Riemannian geometries describing gravity beyond General Relativity and exhibits nice ...
Victor Ilisie
doaj   +1 more source

Comparison of primordial tensor power spectra from the deformed algebra and dressed metric approaches in loop quantum cosmology

, 2015
Loop quantum cosmology tries to capture the main ideas of loop quantum gravity and to apply them to the Universe as a whole. Two main approaches within this framework have been considered to date for the study of cosmological perturbations: the dressed ...
Barrau, A., Bolliet, B., Grain, J., Linsefors, L., Stahl, C.   +4 more
core   +3 more sources