Gravitation and Cosmology最新文献

{"title":"Cosmology with Rotation in Hybrid Inflation","authors":"O. V. Sandakova,&nbsp;V. F. Panov,&nbsp;E. V. Kuvshinova","doi":"10.1134/S0202289325700276","DOIUrl":"10.1134/S0202289325700276","url":null,"abstract":"<p>A cosmological scenario with dark energy (DE), rotation and hybrid inflation is proposed with the Bianchi type II metric. At the stage of early inflation, the decay of a double scalar field is considered, with a transition to the ultrarelativistic stage of the universe evolution. A solution to the Einstein equations and scalar field equations is found, together with the energy density and pressure components of an anisotropic fluid. A description of hybrid inflation with slow and fast rolling stages is obtained. The evolution of the rotation of DE, modeled by an anisotropic fluid, is investigated. We suppose that the anisotropic fluid does not transfer rotation to other types of matter, and at the Friedmann stages, it does not transfer rotation to produced matter particles. Then we obtain the result that if our scenario models the entire evolution of the Universe, assuming that the scale factor of the universe evolves as it inflates and then expands from the Planck value to the current size of the observable Universe, we can assume that in the modern era, the rotational velocity of the anisotropic fluid is of the order <span>(omega_{c}=10^{-11})</span>/year. Important observations have been made on the application of our work with Sbytov and the results from the James Webb telescope in order to detect the possible rotation of the Universe.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 3","pages":"401 - 407"},"PeriodicalIF":1.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934758","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}

{"title":"A Study of a Riemann Soliton in a Perfect Fluid Space-Time and (boldsymbol{f(r,T)})-Gravity","authors":"Sampa Pahan,&nbsp;Souvik Dutta","doi":"10.1134/S0202289325700240","DOIUrl":"10.1134/S0202289325700240","url":null,"abstract":"<p>We carry out geometric attribution of perfect fluid space-time in terms of a Riemann soliton with a torse forming vector field. It is shown that a perfect fluid space-time becomes a dark fluid space-time when we represent the timelike velocity vector field to be a torse-forming vector field. Next, we have investigated the nature of a Riemann soliton in perfect fluid space-time under certain curvature conditions in terms of the cosmological constant, the gravitational constant, energy density and isotropic pressure. We have also constructed an example of Riemann soliton in perfect fluid space-time. Finally, we have classified the Riemann soliton in a perfect fluid space-time obeying <span>(f(r,T))</span>-gravity in terms of energy density and isotropic pressure.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 3","pages":"366 - 374"},"PeriodicalIF":1.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934755","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}

{"title":"Generalized Robertson–Walker Space-Times Admitting (boldsymbol{eta})-Ricci–Yamabe Solitons","authors":"Ansari Rakesh Baidya,&nbsp;Uday Chand De,&nbsp;Abul Kalam Mondal","doi":"10.1134/S0202289325700288","DOIUrl":"10.1134/S0202289325700288","url":null,"abstract":"<p>We study <span>(eta)</span>-Ricci–Yamabe solitons and gradient <span>(eta)</span>-Ricci–Yamabe solitons in generalized Robertson–Walker space-times . At first, we provide an example of an <span>(eta)</span>-Ricci–Yamabe soliton. Next, we prove that if a generalized Robertson–Walker space-time admits an <span>(eta)</span>-Ricci–Yamabe soliton or a gradient <span>(eta)</span>-Ricci–Yamabe soliton, then it becomes a perfect fluid space-time. As a consequence, we obtain several interesting corollaries.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 3","pages":"408 - 414"},"PeriodicalIF":1.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934759","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}

{"title":"Gravitational Field of a Self-gravitating Continuous Medium, Dark Matter and Disk Galaxies","authors":"V. M. Zhuravlev","doi":"10.1134/S0202289325700173","DOIUrl":"10.1134/S0202289325700173","url":null,"abstract":"<p>A new representation for the field strength of the quasiclassical gravitational field of a continuous medium is proposed, which makes it possible to describe the effect of hidden mass or dark matter in a new way. The connection of the new representation with the properties of a continuous medium and the role of these properties in the formation of the hidden mass effect are discussed. Based on the results obtained, a new model of the structure of disk galaxies and their own evolution under dynamic equilibrium conditions is being investigated. A general classification of possible types of spatial structures of disk galaxies is given. The existence conditions of disk galaxies with bulges and jets, as well as ring structures, are considered. A qualitative analysis of possible variants of the galaxies’ own evolution and the conditions of their spatial oscillations is carried out.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 3","pages":"291 - 311"},"PeriodicalIF":1.0,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144934793","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}

{"title":"Cosmological Model with a Scalar Field Assisted Dark Energy Component of the Universe","authors":"Mithun Bairagi","doi":"10.1134/S0202289325700100","DOIUrl":"10.1134/S0202289325700100","url":null,"abstract":"<p>We present a cosmological model that incorporates a minimally coupled canonical scalar field, dark energy, and dark matter components of the cosmos within the context of general relativity (GR) based gravity. Using the first integral method, we solve the homogeneous scalar field equation with the Higgs potential and obtain some new analytical solutions for the scalar field <span>(phi)</span>. These solutions are effective in explaining the Universe’s late-time acceleration phase. We use the <span>(chi^{2})</span>-minimization technique to compare our theoretical findings with a variety of observational data in order to evaluate the validity of this theoretical model. We make use of the observational data from three compilations of the Type Ia supernovae (SN Ia) dataset: the Union 2.1 compilation, the joint light-curve analysis (JLA), and the Pantheon sample. We calculate the current values of some significant cosmological parameters, such as the present values of the Hubble parameter (<span>((H_{0}))</span> and the deceleration parameter (<span>((q_{0}))</span>), and these values are in good agreement with the most recent observational evidence. As a function of redshift <span>(z)</span>, we also look at the evolution of the Equation of State parameters (<span>(w_{textrm{DE}}(z))</span> and <span>(w_{phi}(z))</span>), the density parameters, the potential (<span>(V(z))</span>), and the deceleration parameter (<span>(q(z))</span>).</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"210 - 220"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145164750","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}

{"title":"Magnetic Mirror Stars in Five Dimensions#","authors":"K. A. Bronnikov,&nbsp;S. V. Bolokhov,&nbsp;M. V. Skvortsova","doi":"10.1134/S0202289325700045","DOIUrl":"10.1134/S0202289325700045","url":null,"abstract":"<p>We discuss a class of solutions of multidimensional gravity which are formally related to black-hole solutions but can observationally look like compact stars whose surface reflects back all particles or signals getting there. Some particular examples of such solutions are presented and studied, including those with a magnetic field in Maxwell or nonlinear electrodynamics (NED) in five dimensions. For NED as a possible source for magnetic mirror stars, we formulate a methodology of solving the 5D Einstein-NED equations and point out the conditions under which there always exist mirror star solutions. We also note that some of the Einstein–Maxwell solutions under consideration are discussed in the literature and called “topological stars” due to the circular topology of the fifth dimension.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"166 - 173"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165179","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}

{"title":"Investigations on Relativistic Magneto-Fluid Space–Time Stuffing in (boldsymbol{F(R)}) Gravity and Ricci Solitons","authors":"Zosangzuala Chhakchhuak,&nbsp;Jay Prakash Singh","doi":"10.1134/S0202289325700082","DOIUrl":"10.1134/S0202289325700082","url":null,"abstract":"<p>The present paper focuses on relativistic magneto-fluid space–time in the framework of <span>(F(R))</span> gravity theory. We characterize the relativistic magneto-fluid space–time stuffing in <span>(F(R))</span>-gravity and obtain the expression for the Ricci tensor, scalar curvature, and the equation of state. Also, by taking a Ricci soliton as its metric, we acquire the conditions under which the soliton shrinks, remains steady or grows when taking Killing and torse forming vector fields. We also establish the emergence of a black hole and a trapped surface outside the black hole and argue that the trapped surface is completely surrounded by the event horizon in the context of a relativistic magneto-fluid space–time stuffed in <span>(F(R))</span>-gravity when it admits a shrinking Ricci soliton by putting restrictions on the scalar function <span>(omega)</span> and the first derivative of <span>(F(R))</span>. It is also shown that when the space–time admits a gradient Ricci soliton as its metric, the gravitational dynamics is solely influenced by the magnetic field strength, magnetic permeability and density of the magnetic fluid, which further affects the total pressure on the considered space–time.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"195 - 204"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165173","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}

{"title":"Some Features of the Extended Phase Space Approach to Quantization of Gravity#","authors":"T. P. Shestakova","doi":"10.1134/S020228932570001X","DOIUrl":"10.1134/S020228932570001X","url":null,"abstract":"<p>In this paper, I emphasize those features of the extended phase space approach to quantization of gravity that distinguish it among other approaches. First of all, it is the conjecture on a nontrivial topology of the Universe which was supported by Wheeler, Hawking, and other founders of quantum gravity. However, this conjecture appears to be in contradiction with the assumption on asymptotic states that is used in the path integral quantization of gauge theories. The presence of asymptotic states ensures gauge invariance of the theory, but, in the case of gravity, these states exist only in asymptotically flat space–times, which restricts possible topologies. Then we have two ways. The first way is to consider only asymptotically flat space–times. In fact, it reduces quantum gravity to quantum field theory in a given background. The second way is to reject the assumption on asymptotic states. In the case of a nontrivial topology, one cannot cover the whole space–time with a single coordinate system. One has to introduce various reference frames fixed by different gauge conditions in different space–time regions. The Hamiltonian describing a gravitating system will depend on gauge conditions. It leads to the conclusion that a unitary evolution may be broken down. This conclusion cannot be obtained in approaches based on the Wheeler–DeWitt equation or making use of the assumption on asymptotic states. The assessment of this conclusion is given.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"125 - 132"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165176","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}

{"title":"Master Space-Teleparallel Supergravity: Implications for Special Cases","authors":"G. Ter-Kazarian","doi":"10.1134/S0202289325700033","DOIUrl":"10.1134/S0202289325700033","url":null,"abstract":"<p>We propose the theory of <i>Master space</i>-Teleparallel Supergravity (<span>(widetilde{textrm{MS}}_{p})</span>-TSG), subject to certain rules, as a local extension of the author’s recent theory of global MS<span>({}_{p})</span>-SUSY [1]. The latter reviews the physical processes underlying the standard Lorenz code of motion and its deformation tested in experiments for ultra-high energy cosmic ray and TeV-<span>(gamma)</span> photons observed. A local MS<span>({}_{p})</span>-SUSY theory was originally conceived as a theory of <span>(widetilde{textrm{MS}}_{p})</span>-supergravity (SG). The action of the simple <span>(widetilde{textrm{MS}}_{p})</span>-SG theory includes the Hilbert term for a <i>fictitious</i> graviton coexisting with a <i>fictitious</i> gravitino (sparticle) described by the Rarita–Scwinger kinetic term. Using Palatini’s formalism extended in a plausible fashion to this theory, we reinterpret the flat <span>(widetilde{textrm{MS}}_{p})</span>-SG theory with Weitzenböck torsion as the theory of <span>(widetilde{textrm{MS}}_{p})</span>-TSG having the gauge <i>translation</i> group in the tangent bundle. The Hilbert action here vanishes, and the gravitino action loses its spin connections, so that the accelerated reference frame has a Weitzenböck torsion induced by gravitinos. The action of <span>(widetilde{textrm{MS}}_{p})</span>-TSG is invariant under the Poincaré supergroup and under diffeomorphisms. The Weitzenböck connection defines the acceleration through force equation, with torsion (or contortion) playing the role of force. The accelerated particle mechanics in 4D Minkowski space–time is discussed. We develop a general deformation of the flat master space (MS<span>({}_{p}towidetilde{textrm{MS}}_{p})</span>), and show that the occurrence of <i>inertial effects</i> is clearly caused by that. We supplement the <span>(widetilde{textrm{MS}}_{p})</span>-TSG theory by considering the consequences for the Newtonian limit, the uniform acceleration field and the relativistic inertial force in Minkowski and semi-Riemannian spaces. The Weak Equivalence Principle (WEP) is a consequence of the theory.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"145 - 165"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165178","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}

{"title":"Four-Parameter (boldsymbol{chi}^{mathbf{2}})-Test Discloses a Suitable Hubble Parameter for Diffusive Interaction in the Dark Sector: Prediction of a Super-Exponentially Expanding Emergent Universe","authors":"Giridhari Deogharia,&nbsp;Shreyashi Roy","doi":"10.1134/S0202289325700136","DOIUrl":"10.1134/S0202289325700136","url":null,"abstract":"<p>In order to evaluate this work, cosmic matter in the form of diffusive barotropic fluid has been used to represent the flat FLRW Universe. The cosmic scalar field <span>((phi_{textrm{diffusion}}))</span> is taken as a diffusion process, causing the diffusive fluid to dissipate. Also, three kinds of parametrizations of energy densities are introduced. A suitable hybrid scale factor is used to construct a four-parameter model. To approximate the cosmological parameters, the <span>(chi^{2})</span>-test is introduced. To find the nature of the expanding universe, the cosmological parameters are analyzed. The ultimate fate of the universe can be predicted through this model.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"31 2","pages":"252 - 259"},"PeriodicalIF":1.0,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145164296","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}