Zobrazeno 1 - 10
of 139
pro vyhledávání: '"Christos G. Tsagas"'
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 84, Iss 10, Pp 1-11 (2024)
Abstract Bianchi cosmologies are “natural” anisotropic extensions of the Friedmann universes and they have long been used to investigate the cosmological implications of anisotropy. The latter introduces new ingredients to the standard scenarios,
Externí odkaz:
https://doaj.org/article/a3282f2a2ec24d20b4cf51860518eedc
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 83, Iss 3, Pp 1-14 (2023)
Abstract We study the potential effects of spacetime non-metricity in cosmology. In the spirit of Einstein–Cartan gravity, but with non-metricity replacing torsion, we consider the Einstein–Hilbert action and assume zero torsion. Adopting certain
Externí odkaz:
https://doaj.org/article/fd26e1790331449086b5935de00c8482
Autor:
Christos G. Tsagas
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 82, Iss 6, Pp 1-10 (2022)
Abstract Large-scale bulk peculiar motions introduce a characteristic length scale, inside which the local kinematics are dominated by peculiar-velocity perturbations rather than by the background Hubble expansion. Regions smaller than the aforementi
Externí odkaz:
https://doaj.org/article/1d7bd757cd71443ca34c5e2aa6948c57
Autor:
Christos G. Tsagas
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 81, Iss 8, Pp 1-13 (2021)
Abstract Typical observers in the universe do not follow the smooth Hubble expansion, but move relative to it. Such bulk peculiar motions introduce a characteristic scale that is closely analogous to the familiar Jeans length. This “peculiar Jeans
Externí odkaz:
https://doaj.org/article/a767c3ba11aa44889e3e6a2545608115
Autor:
Eleni Tsaprazi, Christos G. Tsagas
Publikováno v:
European Physical Journal C: Particles and Fields, Vol 80, Iss 8, Pp 1-9 (2020)
Abstract We consider the linear kinematics of large-scale peculiar motions in a perturbed Friedmann universe. In so doing, we take the viewpoint of the “real” observers that move along with the peculiar flow, relative to the smooth Hubble expansi
Externí odkaz:
https://doaj.org/article/0872aee3f9f44f2a8d07d6cb4d0ef8e2
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 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
Autor:
Myrto Maglara, Christos G. Tsagas
Large-scale peculiar motions are commonplace in our universe. Nevertheless, their origin, evolution and implications are still largely unknown. It is generally assumed that bulk motions are a relatively recent addition to the universal kinematics, tr
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::37f01b6d8f5014aaa692c31f77ce60ae
http://arxiv.org/abs/2207.09824
http://arxiv.org/abs/2207.09824
We study a parametrization of the deceleration parameter in a tilted universe, namely a cosmological model equipped with two families of observers. The first family follows the smooth Hubble flow, while the second are the real observers residing in a
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::901987eb411d40839e91a5790d69bb6e
http://arxiv.org/abs/2202.00962
http://arxiv.org/abs/2202.00962
Publikováno v:
Astrophysics and Space Science. 366
Although bulk peculiar motions are commonplace in the universe, most theoretical studies either bypass them, or take the viewpoint of the idealised Hubble-flow observers. As a result, the role of these peculiar flows remains largely unaccounted for,
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::3399e6c3a5a0cfe72d55c43c7a87b878
https://doi.org/10.1007/s10509-021-03995-7
https://doi.org/10.1007/s10509-021-03995-7