Gravitation and Cosmology最新文献_第6页

Biquaternionic Analysis, Cyclic Quaternionic Fields, and Generalization of the Kerr–Penrose Theorem 双四元分析、循环四元场和克尔-彭罗斯定理的广义化

IF 1.2 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2024-04-04 DOI: 10.1134/S0202289324010079

V. V. Kassandrov, J. A. Rizcallah

引用次数: 0

Dynamics of Modified Rényi Holographic Dark Energy in Sáez–Ballester Theory of Gravitation 萨伊斯-巴勒斯特引力理论中的修正雷尼全息暗能量动力学

IF 1.2 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2024-04-04 DOI: 10.1134/S0202289324010031

Jumi Bharali

引用次数: 0

Proof for the Weak and the Strong Energy Conditions Theorems in Einstein–Yang–Mills Theories 爱因斯坦-杨-米尔斯理论中弱和强能量条件定理的证明

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040096

Alcides Garat

引用次数: 0

Studies of Density Contrast of Cold Dark Matter in Cosmological Radiation and Dark Energy Background: A Symmetry-Based Approach 宇宙辐射和暗能量背景中冷暗物质密度对比研究:一种基于对称性的方法

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040084

Aritra Ganguly, Amitava Choudhuri

{"title":"Studies of Density Contrast of Cold Dark Matter in Cosmological Radiation and Dark Energy Background: A Symmetry-Based Approach","authors":"Aritra Ganguly, Amitava Choudhuri","doi":"10.1134/S0202289323040084","DOIUrl":"10.1134/S0202289323040084","url":null,"abstract":"We study the density contrast equations for cold dark matter (CDM) in the cosmological radiation and dark energy (DE) background. We provide a general prescription for the derivation of the aforesaid density contrast equations of the CDM using the metric perturbation technique. In particular, in the early radiation domination, the density contrast equation, the so-called Mészáros equation is derived, considering a four-fluid model, while on the other hand, in the late time DE domination, the “w-Mészáros equation” is derived, using the two-fluid system of CDM and DE. In the first case, we find eight-parameter Lie symmetries, while in the second case we also obtain eight symmetry generators of the “w-Mészáros equation,” each for the values of the equation-of-state parameter (w=-2/3) and (-1). Finding group-invariant solutions using the invariant curve condition for both cases, we have investigated the sub-horizon evolution of density contrasts of the CDM and provided a qualitative study on the nature of evolution of the CDM perturbations. The density contrast of CDM shows no growth during the radiation dominated era, but growth is seen just at the time of matter-radiation equality. The freezing or stagnation of the density contrast of the CDM prior to the matter-radiation equilibrium is due to the rapid expansion of the radiation background at early time, while the decay of the density contrast with increasing scale factor, which results in suppression in the growth of the inhomogeneity, is due to the DE dominated accelerated expansion.","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 4","pages":"419 - 431"},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138437195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Photon Spheres near Dilatonic Dyon-Like Black Holes in a Model with Two Abelian Gauge Fields and Two Scalar Fields 两个阿贝尔规范场和两个标量场模型中类狄龙黑洞附近的光子球

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040114

V. D. Ivashchuk, A. N. Malybayev, G. S. Nurbakova, G. Takey

{"title":"Photon Spheres near Dilatonic Dyon-Like Black Holes in a Model with Two Abelian Gauge Fields and Two Scalar Fields","authors":"V. D. Ivashchuk, A. N. Malybayev, G. S. Nurbakova, G. Takey","doi":"10.1134/S0202289323040114","DOIUrl":"10.1134/S0202289323040114","url":null,"abstract":"Dilatonic dyon-like black hole solutions with two (color) charges (Q_{1}) and (Q_{2}) (electric and magnetic ones) are considered in a gravitational 4D model with two scalar fields and two 2-forms. Two-dimensional dilatonic coupling vectors (vec{lambda}_{i}), (i=1,2), determining the model, obey the relation (vec{lambda}_{1}vec{lambda}_{2}=1/2). Circular null geodesics in the field of such black holes are explored. The master equation for the photon sphere radius (R) is derived. A conjecture is suggested on the existence and uniqueness of the solution to the master equation with (R>R_{g}), where (R_{g}) is the horizon radius. This conjecture is varified for certain special cases, e.g., for a charge symmetric configuration: (Q_{1}^{2}=Q_{2}^{2}). In this charge symmetric case, we present a relation for the spectrum of quasinormal modes of a test massless scalar field in the eikonal approximation, and an example of circular orbits of a massive particle.","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 4","pages":"411 - 418"},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138437132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

GZK Cutoff in Presence of a Specified Modified Dispersion Relation 存在特定修正色散关系的GZK截止

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S020228932304014X

Arash Majidian, Mehdi Jafari Matehkolaeer

引用次数: 0

Formation of Supermassive Nuclei of Black Holes in the Early Universe by the Mechanism of Scalar-Gravitational Instability. I. Local Picture({}^{1}) 早期宇宙中超大质量黑洞核形成的尺度引力不稳定性机制。一、当地情况({}^{1})

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040102

Yu. G. Ignat’ev

{"title":"Formation of Supermassive Nuclei of Black Holes in the Early Universe by the Mechanism of Scalar-Gravitational Instability. I. Local Picture({}^{1})","authors":"Yu. G. Ignat’ev","doi":"10.1134/S0202289323040102","DOIUrl":"10.1134/S0202289323040102","url":null,"abstract":"On the basis of the formulated and proven similarity properties of cosmological models based on a statistical system of degenerate scalarly charged fermions, as well as the previously identified mechanism of scalar-gravitational instability of cosmological models, a numerical and analytical study of the formation of supermassive black hole nuclei in the early Universe is carried out. A mathematical model of the evolution of spherical perturbations is constructed, making itt possible to reveal the main regularities of the process of evolution of collapsing masses and the dependence of the parameters of forming black holes on the fundamental parameters of the cosmological model and the wavelength of gravitational perturbations. In this case, the mass loss of the black hole due to quantum evaporation is taken into account. A stable tendency for the early formation of supermassive black hole nuclei in the class of cosmological models under study is shown, and a close connection between the growth of masses of spherical perturbations and the nature of the singular points of these models is shown.","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 4","pages":"327 - 344"},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138437103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

“New Inflation” for a Bianchi Type IX Cosmological Model with Rotation and Dark Energy 包含旋转和暗能量的Bianchi IX型宇宙学模型的“新暴胀”

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040175

V. F. Panov, O. V. Sandakova, E. V. Kuvshinova

引用次数: 0

Dynamical Analysis of a Charged Spherical Star in (boldsymbol{R-}boldsymbol{beta}boldsymbol{R}_{boldsymbol{c}}mathbf{tanh}boldsymbol{(R/R_{c})+}boldsymbol{xi}boldsymbol{RT}) Gravity 带电球星在(boldsymbol{R-}boldsymbol{beta}boldsymbol{R}_{boldsymbol{c}}mathbf{tanh}boldsymbol{(R/R_{c})+}boldsymbol{xi}boldsymbol{RT})重力作用下的动力学分析

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040047

M. Z. Bhatti, Z. Yousaf, M. Yousaf

{"title":"Dynamical Analysis of a Charged Spherical Star in (boldsymbol{R-}boldsymbol{beta}boldsymbol{R}_{boldsymbol{c}}mathbf{tanh}boldsymbol{(R/R_{c})+}boldsymbol{xi}boldsymbol{RT}) Gravity","authors":"M. Z. Bhatti, Z. Yousaf, M. Yousaf","doi":"10.1134/S0202289323040047","DOIUrl":"10.1134/S0202289323040047","url":null,"abstract":"We illustrate the dynamical instability of charged spherical fluid configuration with anisotropic conditions in nonminimally coupled (f(R,T)) theory of gravitation, where (R) is the Ricci scalar and (T) is the trace of the energy momentum-tensor. We investigate both modified field equations and continuity equations to provide some extra degrees of freedom under the constraints of a specific considered form of (f(R,T)) gravity. We examine how small changes in geometric and material profiles affect the fluid’s collapsing structure via a perturbation scheme. We study the unstable eras using Newtonian ((mathbb{N})) and post-Newtonian (pN) approximations by applying some significant constraints on the collapse equation. Our findings demonstrate that the stiffness parameter (Gamma) has a substantial influence on the identification of unstable phases for our charged stellar geometry. We conclude that some correction terms that are dark source terms, which appear due to (f(R,T)) gravity, lead to an unstable structure/phase throughout the evolutionary process.","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 4","pages":"486 - 502"},"PeriodicalIF":0.9,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138437219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the Stability of Spherically Symmetric Space-Times in Scalar-Tensor Gravity 标量张量引力中球对称时空的稳定性

IF 0.9 4区物理与天体物理

Gravitation and Cosmology Pub Date : 2023-11-23 DOI: 10.1134/S0202289323040059

K. A. Bronnikov, S. V. Bolokhov, M. V. Skvortsova, K. Badalov, R. Ibadov

引用次数: 0