Results 111 to 120 of about 299,841 (224)

Signature of f(R) gravity via Lemaître–Tolman–Bondi inhomogeneous perturbations

European Physical Journal C: Particles and Fields
We analyze inhomogeneous cosmological models in the local Universe, described by the Lemaître–Tolman–Bondi (LTB) metric and developed using linear perturbation theory on a homogeneous and isotropic Universe background. Focusing on the different evolution
Tiziano Schiavone, Giovanni Montani
doaj   +1 more source

Cosmic anisotropy with reduced relativistic gas

European Physical Journal C: Particles and Fields, 2018
The dynamics of cosmological anisotropies is investigated for Bianchi type I universe filled by a relativistic matter represented by the reduced relativistic gas model (RRG), with equation of state interpolating between radiation and matter.
Simpliciano Castardelli dos Reis, Ilya L. Shapiro   +1 more
doaj   +1 more source

On the Effects of the Solar Wind Structure in the Global Distribution of dBH/dt ${\text{dB}}_{H}/\text{dt}$ Spikes During Geomagnetic Storms

Journal of Geophysical Research: Space Physics, Volume 131, Issue 9, September 2026.
Abstract Variations in the solar wind, particularly those associated with interplanetary coronal mass ejections (ICMEs) and high‐speed streams (HSSs), drive geomagnetic disturbances that produce rapid changes in the ground magnetic field. These variations, commonly quantified by the time derivative of the horizontal magnetic field dBH/dt $\left({\text ...
José P. Marchezi, Amy Keesee, Michael Coughlan, Raman Mukundan, Victor Pinto, Ligia A. Da Silva, Livia R. Alves, Hyunju Connor, Don Hampton   +8 more
wiley   +1 more source

Gauge transformations and gauge-invariant cosmological perturbations [PDF]

, 2022
The study of cosmological perturbations brought to light misleading interpretations and solutions without physical meaning. In fact the invariance of General Relativity leads to the fact that different gauges, which yield to different solutions, are ...
Pugno, Anna
core  

Cosmic Ray Anisotropy Generated by the June 22nd 2015 Interplanetary Events

Journal of Geophysical Research: Space Physics, Volume 131, Issue 9, September 2026.
Abstract On 22 June 2015, the near Earth interplanetary space was perturbed by a series of high‐speed streamers and interplanetary coronal mass ejections associated with an active region and two low‐latitude coronal holes. The interaction of these disturbances gave rise to the complex solar wind structure observed at 1 au.
A. Lara, K. P. Arunbabu, T. Niembro
wiley   +1 more source

Extragalactic and cosmological tests of gravity theories with additional scalar or vector fields [PDF]

, 2011
Despite the many successes of the current standard model of cosmology on the largest physical scales, it relies on two phenomenologically motivated constituents, cold dark matter and dark energy, which account for approximately 95% of the energy-matter ...
Feix, Martin
core   +2 more sources

On the Perturbed Friedmann Equations in Newtonian Gauge

Universe
Based on Newtonian mechanics, in this article, we present a heuristic derivation of the Friedmann equations, providing an intuitive foundation for these fundamental relations in cosmology.
Jaume de Haro, Emilio Elizalde, Supriya Pan   +2 more
doaj   +1 more source

Hamilton-Jacobi formalism of tachyon inflation and cosmological perturbations

上海师范大学学报. 自然科学版, 2014
We study the cosmological inflation models driven by the rolling tachyon field which has a Born-Infeld-type action.We drive the Hamilton-Jacobi equation for the cosmological dynamics of tachyon inflation and the mode equations for the scalar and tensor ...
LIU Daojun
doaj   +1 more source

Analytical Modeling of Hot Ion Interchange Injections in Saturn's Magnetosphere

Journal of Geophysical Research: Space Physics, Volume 131, Issue 9, September 2026.
Abstract Cassini's CHarge Energy Mass Spectrometer (CHEMS) instrument collected energetic plasma data from 2004 to 2017, including hundreds of observations of small‐scale nearly dispersionless “local” injection events into the inner magnetosphere. This study assesses whether these interchange‐like injections are a channel‐like structure still connected
Michael W. Liemohn, Jenna Syposs, Abigail R. Azari, Erika Y. Hathaway, Alexandra K. Roosnovo   +4 more
wiley   +1 more source

Classical and thermodynamic stability of black holes [PDF]

, 2010
We consider the stability of black holes within both classical general relativity and the semiclassical thermodynamic description. In particular, we study linearised perturbations and their contributions to the gravitational partition function. Exploring

core   +2 more sources