Zobrazeno 1 - 10
of 449
pro vyhledávání: '"John D. Barrow"'
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 12, Pp 1-12 (2020)
Abstract We study the Einstein-aether theory in Weyl integrable geometry. The scalar field which defines the Weyl affine connection is introduced in the gravitational field equation. We end up with an Einstein-aether scalar field model where the inte
Externí odkaz:
https://doaj.org/article/00a2069108804d7ca47dbeef04a78fc9
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 12, Pp 1-13 (2020)
Abstract We construct a formal asymptotic series expansion for a general solution of the Brans–Dicke equations with a fluid source near a sudden singularity. This solution contains 11 independent arbitrary functions of the spatial coordinates as re
Externí odkaz:
https://doaj.org/article/2e2940827352475cba000ad29084cc4c
Autor:
John D. Barrow, Spiros Cotsakis
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 9, Pp 1-11 (2020)
Abstract We generalise Einstein’s formulation of the traceless Einstein equations to f(R) gravity theories. In the case of the vacuum traceless Einstein equations, we show that a non-constant Weyl tensor leads via a conformal transformation to a di
Externí odkaz:
https://doaj.org/article/6741dac5194d4aff8e909f8e55f45541
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 8, Pp 1-17 (2020)
Abstract We investigate the existence of inhomogeneous exact solutions in Weyl Integrable theory with a matter source. In particular, we consider the existence of a dust fluid source while for the underlying geometry we assume a line element which be
Externí odkaz:
https://doaj.org/article/ba8c52a86259434db648d9e6b64cff5b
Autor:
John D. Barrow, Georgia Kittou
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 2, Pp 1-8 (2020)
Abstract We investigate the case of two interacting fluids in homogeneous and isotropic cosmologies with a non-linear interaction term. The interaction term avoids the unrealistic form generally used in the literature, beginning with Tolman, in which
Externí odkaz:
https://doaj.org/article/45834d17238345b1b46bfb4918dcb247
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 79, Iss 10, Pp 1-18 (2019)
Abstract We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term $$f(T_{\mu \nu }T^{\mu \nu })=\alpha \ln (\lambda \,T_{\mu \nu }T^{\mu \nu })$$ f(TμνTμν)=
Externí odkaz:
https://doaj.org/article/ae82e9f56ad0405bb689e57a76cb17fe
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 79, Iss 9, Pp 1-9 (2019)
Abstract We consider Friedmann-like universes with torsion and take a step towards studying their stability. In so doing, we apply dynamical-system techniques to an autonomous system of differential equations, which monitors the evolution of these mo
Externí odkaz:
https://doaj.org/article/034a36480d654724b9a0a8aa96f65c27
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 79, Iss 8, Pp 1-13 (2019)
Abstract We study the cosmological evolution of the field equations in the context of Einstein–Aether cosmology by including a scalar field in a spatially flat Friedmann–Lemaître–Robertson–Walker spacetime. Our analysis is separated into two
Externí odkaz:
https://doaj.org/article/9e27b5b34b9e4d9d9b7a2f46177cc408
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 79, Iss 5, Pp 1-8 (2019)
Abstract We consider the Szekeres universe with an inhomogeneous dust fluid and a homogeneous and isotropic ghost matter source with equation of state $$p_{g}=( \gamma -1) \rho _{g},$$ pg=(γ-1)ρg, where $$\gamma $$ γ is a constant. The field equat
Externí odkaz:
https://doaj.org/article/a7717f7ae5f64fd284c50ef2cd022c28
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 79, Iss 4, Pp 1-12 (2019)
Abstract We consider spatially homogeneous and isotropic cosmologies with non-vanishing torsion, which assumes a specific form due to the high symmetry of these universes. Using covariant and metric-based techniques, we derive the torsional versions
Externí odkaz:
https://doaj.org/article/c908afef5a5d4e9290df17e7a00438e1