Investigation of the magnetized string distribution in the Marder universe with the cosmological term in f(R,T) theory

2020 ◽  
Vol 35 (32) ◽  
pp. 2050263
Author(s):  
Cihan Kömürcü ◽  
Can Aktaş
Keyword(s):  
Electromagnetic Field ◽  
Geometric Structure ◽  
Cosmological Term ◽  
Observation Data ◽  
The Universe ◽  
Astrophysical Observation ◽  
Hilbert Type ◽  
Marder Universe

In this study, we first obtained the cosmological term naturally in the Einstein–Hilbert type effect for the [Formula: see text] theory, then we discussed the magnetized string matter in the Marder universe, later the matter Lagrangian is not equivalent to string dust and we calculated independently for the string dust and the electromagnetic field, and added the magnetized string together. Finally, we studied the physical and geometric structure of the universe, limiting our results to some astrophysical observation data.

scholarly journals Modeling Gamma-Ray SEDs and Angular Extensions of Extreme TeV Blazars from Intergalactic Proton-Initiated Cascades in Contemporary Astrophysical EGMF Models

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 220
Author(s):  
Emil Khalikov
Keyword(s):  
Gamma Rays ◽  
Large Scale ◽  
Gamma Ray ◽  
High Energy ◽  
Cascade Model ◽  
Point Sources ◽  
Spectral Energy ◽  
Observation Data ◽  
Cherenkov Telescopes ◽  
The Universe

The intrinsic spectra of some distant blazars known as “extreme TeV blazars” have shown a hint at an anomalous hardening in the TeV energy region. Several extragalactic propagation models have been proposed to explain this possible excess transparency of the Universe to gamma-rays starting from a model which assumes the existence of so-called axion-like particles (ALPs) and the new process of gamma-ALP oscillations. Alternative models suppose that some of the observable gamma-rays are produced in the intergalactic cascades. This work focuses on investigating the spectral and angular features of one of the cascade models, the Intergalactic Hadronic Cascade Model (IHCM) in the contemporary astrophysical models of Extragalactic Magnetic Field (EGMF). For IHCM, EGMF largely determines the deflection of primary cosmic rays and electrons of intergalactic cascades and, thus, is of vital importance. Contemporary Hackstein models are considered in this paper and compared to the model of Dolag. The models assumed are based on simulations of the local part of large-scale structure of the Universe and differ in the assumptions for the seed field. This work provides spectral energy distributions (SEDs) and angular extensions of two extreme TeV blazars, 1ES 0229+200 and 1ES 0414+009. It is demonstrated that observable SEDs inside a typical point spread function of imaging atmospheric Cherenkov telescopes (IACTs) for IHCM would exhibit a characteristic high-energy attenuation compared to the ones obtained in hadronic models that do not consider EGMF, which makes it possible to distinguish among these models. At the same time, the spectra for IHCM models would have longer high energy tails than some available spectra for the ALP models and the universal spectra for the Electromagnetic Cascade Model (ECM). The analysis of the IHCM observable angular extensions shows that the sources would likely be identified by most IACTs not as point sources but rather as extended ones. These spectra could later be compared with future observation data of such instruments as Cherenkov Telescope Array (CTA) and LHAASO.

scholarly journals Almost-Pseudo-Ricci Symmetric FRW Universe with a Dynamic Cosmological Term and Equation of State

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 205
Author(s):  
Sanjay Mandal ◽  
Avik De ◽  
Tee-How Loo ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
Cosmological Term ◽  
Ricci Scalar ◽  
Energy Conditions ◽  
Late Time ◽  
Frw Universe ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

The objective of the present paper is to investigate an almost-pseudo-Ricci symmetric FRW spacetime with a constant Ricci scalar in a dynamic cosmological term Λ(t) and equation of state (EoS) ω(t) scenario. Several cosmological parameters are calculated in this setting and thoroughly studied, which shows that the model satisfies the late-time accelerating expansion of the universe. We also examine all of the energy conditions to check our model’s self-stability.

scholarly journals LATE TIME ACCELERATION IN 3-BRANE BRANS–DICKE COSMOLOGY

2008 ◽  
Vol 23 (36) ◽  
pp. 3095-3111
Author(s):  
A. ERRAHMANI ◽  
T. OUALI
Keyword(s):  
Cosmological Parameters ◽  
Late Time ◽  
Observation Data ◽  
Energy Component ◽  
Phantom Divide ◽  
Big Rip ◽  
Dimensional Spacetime ◽  
Dark Energy Component ◽  
Phantom Divide Line ◽  
The Universe

In order to investigate more features of the Brans–Dicke cosmology in the five-dimensional spacetime, we explore the solutions of its dynamical systems. A behavior of the universe in its early and late time by means of the scale factor is considered. As a result, we show that it is possible to avoid the big rip singularity and to cross the phantom divide line. Furthermore, we review the dark energy component of the universe and its agreement with the observation data for this 3-brane Brans–Dicke cosmology by means of the cosmological parameters.

COSMOLOGICAL TERM AS A CORRECTION OF METRIC TENSOR FIELD

2001 ◽  
Vol 10 (06) ◽  
pp. 893-904 ◽  
Author(s):  
TAKAO FUKUI
Keyword(s):  
Cosmological Constant ◽  
Tensor Field ◽  
Cosmological Term ◽  
The Other ◽  
Metric Tensor ◽  
Linear Correction ◽  
The Universe

Models of the universe with a cosmological term which is introduced as a correction of the metric tensor field are studied. By revisiting with these models some of the conventional success, we infer that a model with a linear correction is a favourable candidate for a model of the universe. The cosmological constant and the flatness problems are examined in the model. There might be a possibility to solve the other cosmological problems only with the metric tensor field.

scholarly journals Galaxy merging and number vs. apparent magnitude relation for the universe with a time-decaying cosmological term

2006 ◽  
Vol 449 (3) ◽  
pp. 903-916 ◽  
Author(s):  
Z. Komiya ◽  
K. Kawabata ◽  
K. Hirano ◽  
H. Bunya ◽  
N. Yamamoto
Keyword(s):  
Cosmological Term ◽  
Apparent Magnitude ◽  
The Universe

Massive and massless scalar field models for Kaluza–Klein universe in f(R, T) gravity

2019 ◽  
Vol 34 (11) ◽  
pp. 1950066 ◽  
Author(s):  
Can Aktaş
Keyword(s):  
Scalar Field ◽  
Cosmological Term ◽  
Relativity Theory ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Field Equations ◽  
General Relativity Theory ◽  
Text Model ◽  
The Universe ◽  
Kaluza Klein

In this research, we have investigated the behavior of massive and massless scalar field (SF) models (normal and phantom) for Kaluza–Klein universe in [Formula: see text] gravity with cosmological term ([Formula: see text]). To obtain field equations, we have used [Formula: see text] model given by Harko et al. [Phys. Rev. D 84, 024020 (2011)] and anisotropy feature of the universe. Finally, we have discussed our results in [Formula: see text] and General Relativity Theory (GRT) with various graphics.

scholarly journals FRACTIONAL EINSTEIN–HILBERT ACTION COSMOLOGY

2013 ◽  
Vol 28 (14) ◽  
pp. 1350056 ◽  
Author(s):  
V. K. SHCHIGOLEV
Keyword(s):  
Cosmological Model ◽  
Hubble Parameter ◽  
Cosmological Term ◽  
Total Action ◽  
Real Behavior ◽  
New Type ◽  
Original Interpretation ◽  
The Given ◽  
The Universe ◽  
Hilbert Action

We propose a new type of cosmological model derived from the fractional variational principle when it is applied to the gravitational sector of action functional. In contrast to the fractional cosmological model developed earlier by the author from a fractional total action, in our new model the continuity equation remains valid in its usual form. For this model, a lot of exact solutions are obtained from a specific ansatz which is proposed for the cosmological term in this paper. Several examples arising from the given variations of the Hubble parameter with time are provided. Besides, we suggest an original interpretation of the main equations for our model. It supposes that the effective cosmological term could arise as a result of kinematical induction through the nonzero Hubble parameter. With the help of particular example, we demonstrate how this approach could lead our model quite closer to the real behavior of the universe.

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