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Exact Cosmological Models in Modified (boldsymbol{f(R,L_{m})}) Gravity with Observational Constraints 修正(boldsymbol{f(R,L_{m})})重力与观测约束的精确宇宙学模型
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-09-04 DOI: 10.1134/S020228932303012X
Dinesh Chandra Maurya
{"title":"Exact Cosmological Models in Modified (boldsymbol{f(R,L_{m})}) Gravity with Observational Constraints","authors":"Dinesh Chandra Maurya","doi":"10.1134/S020228932303012X","DOIUrl":"10.1134/S020228932303012X","url":null,"abstract":"<p>This study is an investigation of exact cosmological models in modified <span>(f(R,L_{m}))</span> gravity with observational constraints, where <span>(R)</span> is the Ricci scalar, and <span>(L_{m})</span> is the matter Lagrangian for a perfect fluid. We have obtained the field equations using a flat FLRW metric with matter Lagrangian <span>(L_{m}=-p)</span> and <span>(f(R,L_{m})=R/2+alpha L_{m}^{n}-beta)</span>, where <span>(alpha)</span>, <span>(beta)</span>, <span>(n)</span> are positive parameters. We have solved the field equations for the scale factor <span>(a(t))</span> with the equation of state (EoS) <span>(p=omegarho)</span>, where <span>(p)</span> is the isotropic pressure and <span>(rho)</span> is the energy density. We have obtained the scale factor <span>(a(t)=k_{0}[sinh(k_{1}t+k_{2})]^{[2(n+omega-nomega]/[3n(1+omega)]})</span>, where <span>(k_{1}=frac{sqrt{3beta}}{2}frac{n(1+omega)}{n+omega-nomega})</span>, and <span>(k_{0})</span>, <span>(k_{2})</span> are integration constants. Using this scale factor, we have analyzed various cosmological parameters <span>({H_{0},q_{0},j_{0},s_{0},t_{0}})</span> with observational constraints by applying the <span>(chi^{2})</span> test with four observational datasets <span>(H(z))</span>, Union 2.1, JLA and Bined datasets. Also, we have analyzed the Om diagnostic parameter.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 3","pages":"315 - 325"},"PeriodicalIF":0.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4192270","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: 1
Motion of Spinning and Spinning Deviation in Riemannian Geometry 黎曼几何中纺丝运动和纺丝偏差
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S020228932302007X
Magd E. Kahil, Samah A. Ammar, Shymaa A. Refaey
{"title":"Motion of Spinning and Spinning Deviation in Riemannian Geometry","authors":"Magd E. Kahil,&nbsp;Samah A. Ammar,&nbsp;Shymaa A. Refaey","doi":"10.1134/S020228932302007X","DOIUrl":"10.1134/S020228932302007X","url":null,"abstract":"<p>Equations of motion of spinning density for extended objects and tthe corresponding deviation equations are derived. The problem of motion for a variable mass of a spinning extended object is obtained. Spinning fluids may be considered as a special case to express the motion of spinning density for extended objects. Meanwhile, the spinning density tensor can be expressed in terms of the tetrad formalism of general relativity to be regarded as a gauge theory of gravity. The equations of spinning and spinning deviation density tensors have been derived using a specific type of Bazanski Lagrangian.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"186 - 192"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4423051","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
Anisotropic Compact Star Model on Finch–Skea Space-Time Finch-Skea时空的各向异性致密星模型
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020068
Ankita Jangid, B. S. Ratanpal, K. K. Venkataratnam
{"title":"Anisotropic Compact Star Model on Finch–Skea Space-Time","authors":"Ankita Jangid,&nbsp;B. S. Ratanpal,&nbsp;K. K. Venkataratnam","doi":"10.1134/S0202289323020068","DOIUrl":"10.1134/S0202289323020068","url":null,"abstract":"<p>We demonstrate a new anisotropic solution to the Einstein field equations in Finch–Skea space-time. The physical features of a stellar configuration have been studied in previous investigations. We create a model that meets all physical plausibility conditions for a variety of stars and plot graphs for <b>4U 1820-30</b>.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"206 - 212"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4424659","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: 1
On Geometrization of Classical Fields (Model of Embedded Spaces) 经典场的几何化(嵌入空间模型)
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020081
V. I. Noskov
{"title":"On Geometrization of Classical Fields (Model of Embedded Spaces)","authors":"V. I. Noskov","doi":"10.1134/S0202289323020081","DOIUrl":"10.1134/S0202289323020081","url":null,"abstract":"<p>The possibility of geometrization of the gravitational and electromagnetic fields in 4D Finsler space (the Model of Embedded Spaces—MES) is investigated. The model postulates a proper metric set of an <i>element</i> of distributed matter and asserts that space-time is a mutual physical <i>embedding</i> of such sets. The simplest MES geometry is constructed (its <i>relativistic</i> Finsler version) with a connection that depends on the properties of matter and its fields (torsion and nonmetricity are absent). The field hypothesis and the Least Action Principle of the matter-field system lead to Einstein-type and Maxwell-type equations, and their nonlinearity to the <i>anisotropic</i> field contribution to the <i>seed</i> mass of matter. It is shown that the seed matter plays the role of a physical vacuum of the <i>Embedding</i> and determines the cosmological constant. In the special case of a conformal metric, the Maxwell-type equations reduce to the Maxwell equations themselves and a negative electromagnetic contribution. A possible experimental verification of this result is evaluated. The “redshift” effect in an electric field is also mentioned as a method for studying the vacuum and a relic electric charge. A study of the gauge structure of the presented theory is postponed to the future.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"128 - 146"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4424648","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
Photonic Mode in a Space-Time with a Causal Loop: Comparison of D-CTC and S-CTC Models 具有因果环的时空中的光子模式:D-CTC和S-CTC模型的比较
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020111
A. V. Shepelin, V. A. Tomilin, L. V. Il’ichov
{"title":"Photonic Mode in a Space-Time with a Causal Loop: Comparison of D-CTC and S-CTC Models","authors":"A. V. Shepelin,&nbsp;V. A. Tomilin,&nbsp;L. V. Il’ichov","doi":"10.1134/S0202289323020111","DOIUrl":"10.1134/S0202289323020111","url":null,"abstract":"<p>The evolution of a quantized electromagnetic mode in a space-time toy model with nontrivial topology, allowing closed timelike and null world lines, is considered. The physical consequences of adopting an ontological or epistemological view on a quantum state are compared. It is done within a framework of two alternative interpretations of mode evolution—Deutsch’s D-CTC model (ontological) and S-CTC model (epistemological). The future states of the mode (with respect to the causal loop) are calculated for two types of interaction with the mode’s previous version coming from the future. The found differences of the predictions may be helpful for building a future fundamental theory unifying quantum physics and gravity.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"121 - 127"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4426714","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
Canonical Formulation of Embedding Gravity in a Form of General Relativity with Dark Matter 用暗物质的广义相对论形式嵌入重力的标准公式
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020093
S. A. Paston, T. I. Zaitseva
{"title":"Canonical Formulation of Embedding Gravity in a Form of General Relativity with Dark Matter","authors":"S. A. Paston,&nbsp;T. I. Zaitseva","doi":"10.1134/S0202289323020093","DOIUrl":"10.1134/S0202289323020093","url":null,"abstract":"<p>We study embedding gravity, a modified theory of gravity in which our space-time is assumed to be a four-dimensional surface in flat ten-dimensional space. Based on a simple geometric idea, this theory can be reformulated as general relativity with additional degrees of freedom and a contribution to action which can be interpreted as describing dark matter. We study the canonical formalism for such a formulation of embedding gravity. After solving simple constraints, the Hamiltonian is reduced to a linear combination of four first-class constraints with Lagrange multipliers. There still remain six pairs of second-class constraints. Possible ways of taking these constraints into account are discussed. We show that one way of solving the constraints leads to a canonical system going into the previously known canonical formulation of the complete embedding theory with an implicitly defined constraint.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"153 - 162"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4423040","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: 1
Constraining Deceleration, Jerk and Transition Redshift Using Cosmic Chronometers, Type Ia Supernovae and the ISW Effect 利用宇宙天文钟，Ia型超新星和ISW效应约束减速、猛移和跃迁红移
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S020228932302010X
Syed Faisal ur Rahman
{"title":"Constraining Deceleration, Jerk and Transition Redshift Using Cosmic Chronometers, Type Ia Supernovae and the ISW Effect","authors":"Syed Faisal ur Rahman","doi":"10.1134/S020228932302010X","DOIUrl":"10.1134/S020228932302010X","url":null,"abstract":"<p>We present constraints on the deceleration (<span>(q)</span>) and jerk (<span>(j)</span>) parameters using the late-time integrated Sachs-Wolfe effect, type Ia supernovae, and <span>(H(z))</span> data . We first directly measure the deceleration and jerk parameters using the cosmic chronometers data with the Taylor series expression of <span>(H(z))</span>.However, due to the unusual variations in the deceleration parameter with slight changes in other parameters like snap (<span>(s)</span>) and lerk (<span>(l)</span>), we found that direct measurements using the series expansion of <span>(H(z))</span> is not a suitable method for non-<span>(Lambda)</span>CDM models, and so we will need to derive the deceleration parameter after constraining the density parameters and dark energy equation of state. Then we present the derived values of the deceleration parameter from the <span>(Lambda)</span>CDM, WCDM and CPL models. We also discuss the transition redshift <span>(z_{t})</span> in relation with the deceleration parameter. Our best fit values for the deceleration parameter, after combining results from <span>(H(z))</span>, Union 2.1 and NVSS-ISW, are obtained as <span>(-0.5808pm 0.025)</span> for <span>(Lambda)</span>CDM, <span>(-0.61pm 0.15)</span> for both WCDM and CPL models. Our best fit for the combined jerk parameter for the <span>(Lambda)</span>CDM model is <span>(1pm 3.971e-07)</span>, for WCDM it is <span>(1.054pm 0.141)</span>, and for the CPL model it is <span>(1.0654pm 0.1345)</span>. Also, the combined transition redshift is obtained as <span>(0.724pm 0.047)</span> for the <span>(Lambda)</span>CDM model.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"177 - 185"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4427136","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: 1
Axisymmetric Stationary Space-Times of Constant Scalar Curvature in Four Dimensions 四维恒定标量曲率的轴对称静止空间-时间
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020032
Rosikhuna F. Assafari, Emir S. Fadhilla, Bobby E. Gunara,  Hasanuddin, Abednego Wiliardy
{"title":"Axisymmetric Stationary Space-Times of Constant Scalar Curvature in Four Dimensions","authors":"Rosikhuna F. Assafari,&nbsp;Emir S. Fadhilla,&nbsp;Bobby E. Gunara,&nbsp; Hasanuddin,&nbsp;Abednego Wiliardy","doi":"10.1134/S0202289323020032","DOIUrl":"10.1134/S0202289323020032","url":null,"abstract":"<p>We construct a special class of four-dimensional axisymmetric stationary space-times whose Ricci scalar is constant but are not Einstein space-times. We find that this solution has a ring singularity. At the end, we discuss some numerical results for these space-times.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"193 - 205"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4423043","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: 2
Two Slingshots May Detect Ultraweak Features in the Sun’s Gravity 两个弹弓可以探测到太阳引力的超弱特征
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020123
A. P. Yefremov
{"title":"Two Slingshots May Detect Ultraweak Features in the Sun’s Gravity","authors":"A. P. Yefremov","doi":"10.1134/S0202289323020123","DOIUrl":"10.1134/S0202289323020123","url":null,"abstract":"<p>A space experiment aimed at specifying the law of the Sun’s gravity more precisely is discussed. An extended “standard flight” scheme with two gravity assist maneuvers (slingshots) of a space probe near Venus and Earth is suggested, where the slingshots serve as amplifiers of small deflections caused by a deviation of the gravity law from a chosen ansatz. The deviation of the probe’s trajectory from its classic (Newtonian) pattern is calculated in detail using the isotropic Eddington–Robertson metric for the Sun’s gravity field and the “patched conic approximation” method for description of each slingshot. The trajectory deviation in the two-slingshots scheme is roughly assessed, the results indicating a principal possibility to detect the ultraweak distinctive feature of relativistic gravity.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"147 - 152"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4424658","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
Trautman Problem and its Solution for Plane Waves in Riemann and Riemann–Cartan Spaces 黎曼和黎曼-卡坦空间中平面波的Trautman问题及其解
IF 0.9 4区 物理与天体物理
Gravitation and Cosmology Pub Date : 2023-06-10 DOI: 10.1134/S0202289323020044
O. V. Babourova, B. N. Frolov, M. S. Khetczeva, D. V. Kushnir
{"title":"Trautman Problem and its Solution for Plane Waves in Riemann and Riemann–Cartan Spaces","authors":"O. V. Babourova,&nbsp;B. N. Frolov,&nbsp;M. S. Khetczeva,&nbsp;D. V. Kushnir","doi":"10.1134/S0202289323020044","DOIUrl":"10.1134/S0202289323020044","url":null,"abstract":"<p>The Trautman problem determines the conditions under which GWs transfer the information contained in them in an invariant manner. According to the analogy between plane gravitational and electromagnetic waves, the metric tensor of a plane gravitational wave is invariant under the five-dimensional group <span>(G_{5})</span>, which does not change the null hypersurface of the plane wave front. The theorems are proven on the equality to zero for the result of the action of the Lie derivative on the curvature 2-form of a plane GW in Riemann and Riemann–Cartan spaces in the direction determined by the vector generating the group <span>(G_{5})</span>. Thus the curvature tensor of a plane gravitational wave can invariantly transfer the information encoded in the source of the GW.</p>","PeriodicalId":583,"journal":{"name":"Gravitation and Cosmology","volume":"29 2","pages":"103 - 109"},"PeriodicalIF":0.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4426724","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
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