Results 71 to 80 of about 52,296 (249)

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

Effective actions for loop quantum cosmology in fourth-order gravity

European Physical Journal C: Particles and Fields, 2021
Loop quantum cosmology (LQC) is a theory which renders the Big Bang initial singularity into a quantum bounce, by means of short-range repulsive quantum effects at the Planck scale.
Marcello Miranda, Daniele Vernieri, Salvatore Capozziello, Francisco S. N. Lobo   +3 more
doaj   +1 more source

A simple parity violating model in the symmetric teleparallel gravity and its cosmological perturbations

Physics Letters B, 2022
Parity violating models based on the symmetric teleparallel gravity have been considered in the literature, but their applications in cosmology and especially the features in cosmological perturbations have not been fully explored.
Mingzhe Li, Dehao Zhao
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

Shedding light on gravity: Black hole shadows and lensing signatures in Lorentz gauge theory

Nuclear Physics B
Recent advances, including gravitational wave detections and imaging of black hole shadows, have strongly validated general relativity. Nevertheless, ongoing cosmological observations suggest potential limitations of general relativity, spurring interest
Ali Övgün, Mohsen Fathi
doaj   +1 more source

Cosmological perturbations in a class of fully covariant modified theories: application to models with the same background as standard LQC

European Physical Journal C: Particles and Fields, 2018
Bouncing cosmologies are obtained by adding to the Einstein–Hilbert action a term of the form $$\sqrt{-\,g}f(\chi )$$ -gf(χ) , with $$\chi $$ χ a scalar depending on the Hubble parameter only, not on its derivatives, and which is here shown to arise from
Jaume de Haro, Llibert Aresté Saló, Emilio Elizalde   +2 more
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

Non-chaotic dynamics in general-relativistic and scalar-tensor cosmology [PDF]

, 2006
In the context of scalar-tensor models of dark energy and inflation, the dynamics of vacuum scalar-tensor cosmology are analysed without specifying the coupling function or the scalar field potential.
Banerjee N, Biswas T Notari A, Brown M G Freese K Kinney W H, Buniy R V, Calzetta E, Catena R, Easther R, Esposito-Farése G, Fakir R, Fakir R, Fakir R, Fang W, Faraoni, Faraoni V, Faraoni V, Faraoni V, Foster S, Fujii Y, Fujii Y, Glendinning P, Guckenheimer J, Gunzig E, Gunzig E, Holden D J, Liddle A R, Liddle A R, Lu H Q, M N Jensen, Matarrese S Baccigalupi C Perrotta F, Nojiri S Odintsov S D, Page D N, Perrotta F Baccigalupi C, S A Theuerkauf, Toporensky A V, Toporensky A V, Tsujikawa S, V Faraoni, Wald R M, Weinberg S, Will C M   +39 more
core   +2 more sources

Non-commutative classical and quantum fractionary cosmology: anisotropic Bianchi type I case [PDF]

General Relativity and Gravitation
In this work, we will explore the effects of non-commutativity in fractional classical and quantum schemes using the anisotropicc Bianchi Type I cosmological model coupled to a scalar field in the K-essence formalism.
J. Socorro, J. J. Rosales, Leonel Toledo-Sesma   +2 more
semanticscholar   +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