Results 21 to 30 of about 11,605 (193)
Advances in High Energy Physics, Volume 2022, Issue 1, 2022., 2022 In this paper, we have investigated the density perturbations and cosmological evolution in the FLRW universe in the presence of a cosmic magnetic field, which may be assumed to mimic primordial magnetic fields. Such magnetic fields have sufficient strength to influence galaxy formation and cluster dynamics, thereby leaving an imprint on the CMB ...
Samarjit Chakraborty +2 more
wiley +1 more source
How Extra Symmetries Affect Solutions in General Relativity
Universe, 2020 To get exact solutions to Einstein’s field equations in general relativity, one has to impose some symmetry requirements. Otherwise, the equations are too difficult to solve.
Aroonkumar Beesham, Fisokuhle Makhanya
doaj +1 more source
On the initial singularity in Kantowski–Sachs spacetime
European Physical Journal C: Particles and Fields, 2021 The emergent universe scenario is a proposal for resolving the Big Bang singularity problem in the standard Friedmann–Lemaitre–Robertson–Walker cosmology. In the context of this scenario, the Universe originates from a nonsingular static state.
Elham Ghorani, Yaghoub Heydarzade
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Causality of the brane universe [PDF]
, 2000 Causal structure of the brane universe with respect to null geodesics in the bulk spacetime is studied. It is pointed out that apparent causality violation is possible for the brane universe which contains matter energy. It is also shown that there is no
C. Csáki +15 more
core +4 more sources
Advances in High Energy Physics, Volume 2022, Issue 1, 2022., 2022 We propose generalized uncertainty principle (GUP) with an additional term of quadratic momentum motivated by string theory and black hole physics and providing a quantum mechanical framework for the minimal length uncertainty, at the Planck scale.
Abdel Magied Diab +2 more
wiley +1 more source
Thermodynamics of the FLRW apparent horizon
Physics Letters B, 2023 To investigate the relationship between gravity and thermodynamics in the case of dynamic systems, we interpret the apparent horizon of the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime as a thermodynamic system.
Luis M. Sánchez, Hernando Quevedo
doaj +1 more source
Astronomische Nachrichten, Volume 342, Issue 1-2, Page 81-88, January-February 2021., 2021 The cosmological implications of the Covariant Canonical Gauge Theory of Gravity (CCGG) are investigated. CCGG is a Palatini theory derived from first principles using the canonical transformation formalism in the covariant Hamiltonian formulation. The Einstein‐Hilbert theory is thereby extended by a quadratic Riemann‐Cartan term in the Lagrangian ...
David Vasak +2 more
wiley +1 more source
A new solution for a generalized cosmological wormhole
European Physical Journal C: Particles and Fields, 2023 We find a new exact solution to Einstein field equations that represents a cosmological wormhole embedded in a flat Friedmann–Lemaître–Robertson–Walker universe. The new metric is a generalization of a previous cosmological wormhole solution found by Kim.
Daniela Pérez, Mário Raia Neto
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Phase-Space Analysis of an Einstein–Gauss–Bonnet Scalar Field Cosmology
Mathematics, 2023 We perform a detailed study of the phase-space of the field equations of an Einstein–Gauss–Bonnet scalar field cosmology for a spatially flat Friedmann–Lemaître–Robertson–Walker spacetime.
Alfredo D. Millano +2 more
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Natural vacua in hyperbolic Friedmann-Robertson-Walker spacetimes [PDF]
Physical Review D, 1999 Recent evidence indicates that the Universe is open, i.e., spatially hyperbolic, longstanding theoretical preferences to the contrary notwithstanding. This makes it possible to select a vacuum state, Fock space, and particle definition for a quantized field, by requiring concordance with ordinary flat-spacetime theory at late times. The particle-number
openaire +2 more sources