Zobrazeno 1 - 10
of 232
pro vyhledávání: '"Velten H"'
Publikováno v:
Phys. Rev. D 98, 103501 (2018)
We develop a cosmological model based on action-dependent Lagrangian theories. The main feature here is the nonconservation of the energy momentum tensor due to the nontrivial geometrical construction of the theory. We provide the basic set of equati
Externí odkaz:
http://arxiv.org/abs/1808.02798
Publikováno v:
Phys. Rev. D 98, 123522 (2018)
Cosmological scalar perturbation theory studied in the Newtonian gauge depends on two potentials $\Phi$ and $\Psi$. In General Relativity (GR) they must coincide ($\Phi=\Psi$) in the absence of anisotropic stresses sourced by the energy momentum tens
Externí odkaz:
http://arxiv.org/abs/1807.03357
Publikováno v:
International Journal of Modern Physics D Vol. 28, No. 15, 1950175 (2019)
Extensions of the gravity theory in order to obtain traceless field equations have been widely considered in the literature. The leading example of such class of theories is the unimodular gravity, but there are other possibilities like the mimetic g
Externí odkaz:
http://arxiv.org/abs/1802.01413
Publikováno v:
IJMPD Vol. 28, No. 06, 1950086 (2019)
On the basis of a previously established scalar-tensor extension of the $\Lambda$CDM model we develop an effective fluid approach for the matter growth function. This extended $\Lambda$CDM (henceforth $e_{\Phi}\Lambda$CDM) cosmology takes into accoun
Externí odkaz:
http://arxiv.org/abs/1706.06143
Publikováno v:
Phys. Rev. D 96, 023527 (2017)
It is analyzed the effects of both bulk and shear viscosities on the perturbations, relevant for structure formation in late time cosmology. It is shown that shear viscosity can be as effective as the bulk viscosity on suppressing the growth of pertu
Externí odkaz:
http://arxiv.org/abs/1702.07040
We construct a cosmological scalar-tensor-theory model in which the Brans-Dicke type scalar $\Phi$ enters the effective (Jordan-frame) Hubble rate as a simple modification of the Hubble rate of the $\Lambda$CDM model. This allows us to quantify diffe
Externí odkaz:
http://arxiv.org/abs/1607.03952
Publikováno v:
Phys. Rev. D 93, 124020 (2016)
We analyse the vacuum static spherically symmetric space-time for a specific class of non-conservative theories of gravity based on the Rastall's theory. We obtain a new vacuum solution which has the same structure as the Schwarzschild-de Sitter solu
Externí odkaz:
http://arxiv.org/abs/1602.08513
We discuss the possibility to implement a viscous cosmological model, attributing to the dark matter component a behaviour described by bulk viscosity. Since bulk viscosity implies negative pressure, this rises the possibility to unify the dark secto
Externí odkaz:
http://arxiv.org/abs/1512.00921
Publikováno v:
Phys. Rev. D 92, 044020 (2015)
We calculate static and spherically symmetric solutions for the Rastall modification of gravity to describe Neutron Stars (NS). The key feature of the Rastall gravity is the non-conservation of the energy-momentum tensor proportionally to the space-t
Externí odkaz:
http://arxiv.org/abs/1506.00567
Publikováno v:
MNRAS 452 (2015) 2220-2224
The concordance particle creation model - a class of $\Lambda(t)$CDM cosmologies - is studied using large scale structure (LSS) formation, with particular attention to the integrated Sachs-Wolfe (ISW) effect. The evolution of the gravitational potent
Externí odkaz:
http://arxiv.org/abs/1504.02416