Results 1 to 10 of about 59,420 (206)

Intrinsic Entropy of Squeezed Quantum Fields and Nonequilibrium Quantum Dynamics of Cosmological Perturbations [PDF]

Entropy, 2021
Density contrasts in the universe are governed by scalar cosmological perturbations which, when expressed in terms of gauge-invariant variables, contain a classical component from scalar metric perturbations and a quantum component from inflaton field ...
Jen-Tsung Hsiang, Bei-Lok Hu
doaj   +2 more sources

Cosmological Backreaction from Perturbations [PDF]

, 2007
We reformulate the averaged Einstein equations in a form suitable for use with Newtonian gauge linear perturbation theory and track the size of the modifications to standard Robertson-Walker evolution on the largest scales as a function of redshift for ...
Alnes H, Behrend J, Behrend J Nachtmann O, Biswas T Mansouri R Notari A, Brouzakis N, Buchert T, Buchert T, Buchert T, Doran M, Ellis G F R, Enqvist K, Enqvist K, Futamase T, Georg Robbers, Geshnizjani G, Gourgoulhon E, Hossain G M, Iain A Brown, Ishak M Richardson J Whittington D Garred D, Ishibashi A, Juliane Behrend, Khosravi S Kourkchi E Mansouri R, Kolb E W Matarrese S Notari A Riotto A, Langlois D, Langlois D, Larena J Buchert T, Larena J Buchert T Alimi J-M, Li N Schwarz D J, Li N Schwarz D J, Linder E V, Lu T H-C, Lyth D H, Marra V Kolb E W Matarrese S Riotto A, Martineau P Brandenberger R, Mattsson T Ronkainen M, McClure M L Hellaby C, Parry M F, Rasanen S, Rasanen S, Rasanen S, Riess A G, Vanderveld R A Flanagan E E Wasserman I, Wald R M, Wiltshire D L, Wiltshire D L, York J W, Zalaletdinov R   +46 more
core   +2 more sources

Cosmological tensor perturbations in the Randall-Sundrum model: evolution in the near-brane limit [PDF]

, 2003
We discuss the evolution of cosmological tensor perturbations in the RSII model. In Gaussian normal coordinates the wave equation is non-separable, so we use the near-brane limit to perform the separation and study the evolution of perturbations. Massive
Battye, R. A., Mennim, A., van de Bruck, C.   +2 more
core   +2 more sources

The MESS of cosmological perturbations

Physics Letters B, 2018
We introduce two new effective quantities for the study of comoving curvature perturbations ζ: the space dependent effective sound speed (SESS) and the momentum dependent effective sound speed (MESS).
Antonio Enea Romano, Sergio A. Vallejo Peña   +1 more
doaj   +3 more sources

Cosmological Perturbations in Bouncing Cosmologies and the Case of the Pre-Big Bang Scenario [PDF]

Universe, 2022
Pre-Big Bang cosmology inspired generations of cosmologists in attempts to cure the initial Big Bang singularity using a fundamental length scale as proposed by string theory.
Valerio Bozza
doaj   +2 more sources

Non-minimal coupling influence on the deviation from de Sitter cosmological expansion

European Physical Journal C: Particles and Fields, 2018
We investigate the models of cosmological inflation in generalized scalar–tensor gravity, which we consider as a source of deviation from de Sitter dynamics in the case of GR.
I. V. Fomin, S. V. Chervon
doaj   +3 more sources

Cosmological perturbations in Palatini modified gravity [PDF]

, 2007
Two approaches to the study of cosmological density perturbations in modified theories of Palatini gravity have recently been discussed. These utilise, respectively, a generalisation of Birkhoff's theorem and a direct linearization of the gravitational ...
Arkani-Hamed N Dimopoulos S Dvali G Gabadadze G, Barausse E Sotiriou T P Miller J C, Buchbinder I L, Capozziello S Carloni S Troisi A, Dvali G Turner M S, Fairbairn M Rydbeck S, Heath D, Hu W Sawicki I, James E Lidsey, Kainulainen K Piilonen J Reijonen V Sunhede D, Kainulainen K Reijonen V Sunhede D, Koivisto T, Kotub Uddin, Koyama K, Li B Chan K C Chu M C, Meng X, Meng X H, Meng X H, Meng X H, Meng X H Wang P, Olmo G Komp W, Reza Tavakol, Sahni V, Silvestri A, Sotiriou T P, Sotiriou T P, Spergel D N, Tsujikawa S, Zhang P J, Zwillinger D   +29 more
core   +2 more sources

Quantum State Evolution in an Environment of Cosmological Perturbations

Universe, 2021
We study the pure and thermal states of quantized scalar and tensor perturbations in various epochs of Universe evolution. We calculate the density matrix of non-relativistic particles in an environment of these perturbations.
Zbigniew Haba
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

Linear cosmological perturbations in scalar-tensor-vector gravity

Physics Letters B, 2020
We investigate the cosmological perturbations in the context of a Scalar-Tensor-Vector theory of Gravity known as MOG in the literature. Recent investigations show that MOG reproduces a viable background cosmological evolution comparable to ΛCDM. However,
Sara Jamali, Mahmood Roshan, Luca Amendola   +2 more
doaj   +1 more source