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Topological Casimir Effect in Models with Helical Compact Dimensions 螺旋紧维模型中的拓扑卡西米尔效应
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09849-2
R. M. Avagyan, A. A. Saharian, D. H. Simonyan, G. H. Harutyunyan
{"title":"Topological Casimir Effect in Models with Helical Compact Dimensions","authors":"R. M. Avagyan,&nbsp;A. A. Saharian,&nbsp;D. H. Simonyan,&nbsp;G. H. Harutyunyan","doi":"10.1007/s10511-025-09849-2","DOIUrl":"10.1007/s10511-025-09849-2","url":null,"abstract":"<p>We investigate the influence of the helical compactification of spatial dimension on the local properties of the vacuum state for a charged scalar field with general curvature coupling parameter. A general background geometry is considered with rotational symmetry in the subspace with the coordinates appearing in the helical periodicity condition. It is shown that by a coordinate transformation the problem is reduced to the problem with standard quasiperiodicity condition in the same local geometry and with the effective compactification radius determined by the length of the compact dimension and the helicity parameter. As an application of the general procedure we have considered locally de Sitter spacetime with a helical compact dimension. By using the Hadamard function for the Bunch-Davies vacuum state, the vacuum expectation values of the field squared, current density, and energy-momentum tensor are studied. The topological contributions are explicitly separated and their asymptotics are described at early and late stages of cosmological expansion. An important difference, compared to the problem with quasiperiodic conditions, is the appearance of the nonzero off-diagonal component of the energy-momentum tensor and of the component of the current density along the uncompact dimension.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"520 - 536"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108765","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
Kinematic Distances of Galaxies in the Local Volume 局部体积中星系的运动距离
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09842-9
I. D. Karachentsev, A. A. Popova
{"title":"Kinematic Distances of Galaxies in the Local Volume","authors":"I. D. Karachentsev,&nbsp;A. A. Popova","doi":"10.1007/s10511-025-09842-9","DOIUrl":"10.1007/s10511-025-09842-9","url":null,"abstract":"<p>We consider the kinematic distances to nearby galaxies obtained by the Numerical Action Method (NAM) based on the Cosmic-flow-3 survey data. NAM-distances are compared with 418 high-precision distances measured by the Tip of the Red Giant Branch (TRGB) method using the Hubble Space Telescope. We estimated the average difference &lt;<i>D</i><sub><i>NAM</i></sub> - <i>D</i><sub><i>TRGB</i></sub> &gt; = -0.30 ± 0.08 Mpc and the standard deviation of 1.57 Mpc. Approximately the same difference in the distance scale is obtained in comparison with less accurate distance estimates through the membership of galaxies in known groups or from the Tully-Fisher relation. We conclude that the NAM method provides distance estimates with an accuracy of 20% within the Local Volume, which is valid for ~90% of the sky, except for the regions of the Virgo cluster and the Coma-I group.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"433 - 439"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108761","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
Determining the Frequency Function of Flares and Starspot Coverage in Active Flare Stars Discovered by the Kepler Mission 确定由开普勒任务发现的活跃耀斑恒星的耀斑频率函数和星斑覆盖
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09847-4
A. A. Akopian
{"title":"Determining the Frequency Function of Flares and Starspot Coverage in Active Flare Stars Discovered by the Kepler Mission","authors":"A. A. Akopian","doi":"10.1007/s10511-025-09847-4","DOIUrl":"10.1007/s10511-025-09847-4","url":null,"abstract":"<p>Based on data from the Kepler orbital observatory, this study investigates the most active flare stars, which exhibited 250 or more flares during the Kepler mission period. The main research objectives were: (a) analyzing light curves to identify unique physical characteristics of individual stars; (b) defining the periodic/cyclic flare frequency function (PFFF) of flare stars, associated with axial/orbital rotations; and (c) presenting a novel method for determining starspot coverage using the PFFF and applying this method. The study produced corresponding PFFF values with periodicities close to the star rotation periods. Expected phase distributions of flares were constructed and compared with observed flare distributions for the given rotation period. For all stars examined, this comparison (using the χ<sup>2</sup> criterion) supports the periodicity of flare frequency. It is hypothesized that the starspot distribution of flare stars can be represented by the von Mises circular distribution, with parameters derived from the respective flare frequency function. Estimates of the starspot coverage for the stars studied were obtained.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"487 - 505"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108758","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
Dark Matter in the Presence of Dark Energy 暗能量存在下的暗物质
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09848-3
H. A. Harutyunian
{"title":"Dark Matter in the Presence of Dark Energy","authors":"H. A. Harutyunian","doi":"10.1007/s10511-025-09848-3","DOIUrl":"10.1007/s10511-025-09848-3","url":null,"abstract":"<p>The article considers the issue of changes in the total energy of baryonic objects and their systems in the presence of dark energy, whose carrier, by definition, interacts with all baryonic objects. It is emphasized that dark energy was discovered due to such interaction that accelerates the universe’s expansion. Since dark energy (dark energy carrier) is uniformly distributed, the physical consequences of interaction between the dark energy carrier and baryonic matter are considered at all hierarchical levels of baryonic structures. Drawing on the second law of thermodynamics, the author concludes that under the effect of dark energy, the energy of all baryonic systems gradually increases and their stability declines while the virial value becomes positive and continues to grow for any structures considered to be stable. A similar analysis performed for atomic nuclei reveals that over time, nuclear binding energy decreases, nuclear stability declines, and the nuclear mass increases. This effect gives a new perspective on Ambartsumian’s hypothesis about the existence of superdense matter clumps in the nuclei of stars and galaxies and enables its new interpretation.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"506 - 519"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108766","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
Domain Wall Bianchi Type VI0 Universe in f(R, T) Gravity 域壁Bianchi型VI0宇宙在f（R， T）引力
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09850-9
S. P. Hatkar, D. P. Tadas, S. D. Katore
{"title":"Domain Wall Bianchi Type VI0 Universe in f(R, T) Gravity","authors":"S. P. Hatkar,&nbsp;D. P. Tadas,&nbsp;S. D. Katore","doi":"10.1007/s10511-025-09850-9","DOIUrl":"10.1007/s10511-025-09850-9","url":null,"abstract":"<p>We consider the Bianchi type-VI<sub>0</sub> space time with domain walls in the framework of the modified f (R, T) theory of gravitation. To solve the field equations, we assume that the shear scalar σ is proportional to the expansion scalar θ. We also consider the parametrization of the equation of the state parameter of barotropic fluid and discuss the effect on domain walls. It has been observed that the domain wall may behave like dark energy. Some physical parameters are also discussed in detail.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"537 - 555"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108764","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
Thermodynamics and its Quantum Correction of Vacuum Nonsingular Black Hole 真空非奇异黑洞的热力学及其量子修正
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09851-8
D. Ma, T. Huo, C. Liu
{"title":"Thermodynamics and its Quantum Correction of Vacuum Nonsingular Black Hole","authors":"D. Ma,&nbsp;T. Huo,&nbsp;C. Liu","doi":"10.1007/s10511-025-09851-8","DOIUrl":"10.1007/s10511-025-09851-8","url":null,"abstract":"<p>This paper investigates the thermodynamic properties of vacuum nonsingular black holes. Considering the energy characteristics of the regularity spacetime, we use the modified first law of black hole thermodynamics to calculate the black holes' Hawking temperature, entropy and heat capacity. The obtained temperature is the same as that obtained by the surface gravity and tunneling methods. Also, the entropy is satisfied with the Bekenstein-Hawking area law. Notably, the heat capacity of large-mass black holes diverges, while that of small-mass black holes tends to zero, with a phase transition point existing. Additionally, we consider the quantum gravity effect by using the generalized uncertainty principle to study the quantum corrections of the thermodynamic properties for the vacuum nonsingular black holes. The generalized uncertainty principle introduces a logarithmic correction term to the black hole entropy. Also, the temperature and heat capacity are modified.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"556 - 570"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108763","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
Modified Finch and Skea Stellar Model in Higher Dimensions 改进的高维Finch和Skea恒星模型
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09852-7
A. Jangid, S. Das, B. S. Ratanpal, K. K. Venkataratnam
{"title":"Modified Finch and Skea Stellar Model in Higher Dimensions","authors":"A. Jangid,&nbsp;S. Das,&nbsp;B. S. Ratanpal,&nbsp;K. K. Venkataratnam","doi":"10.1007/s10511-025-09852-7","DOIUrl":"10.1007/s10511-025-09852-7","url":null,"abstract":"<p>Within the framework of higher dimensions, we enhance the model of Pandya and Thomas and assume that the system is anisotropic in the Finch and Skea ansatz. Our model explores various physical parameters in higher dimensions, including mass, energy density, radial and transverse pressures, and the anisotropy factor. We have used graphical technique to analyse the energy conditions, equilibrium conditions, and stability across different dimensions. Furthermore, the mass of a particular compact object have shown to increase with radial parameter as space-time dimensions increase. Additionally, by generating a mass-radius (<i>M</i>-<i>R</i>) plot, we demonstrate the influence of dimensional factor on the maximum mass and radius allowed by our toy model.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"571 - 586"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108762","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
Escape Probability and Average Numbers of Photon Scattering Events. II. Monochromatic Isotropic Scattering in a One-Dimensional Medium and Plane Media 光子散射事件的逃逸概率和平均数量。II.一维介质和平面介质中的单色各向同性散射
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09839-w
D. I. Nagirner, A. V. Dementyev, E. V. Volkov
{"title":"Escape Probability and Average Numbers of Photon Scattering Events. II. Monochromatic Isotropic Scattering in a One-Dimensional Medium and Plane Media","authors":"D. I. Nagirner,&nbsp;A. V. Dementyev,&nbsp;E. V. Volkov","doi":"10.1007/s10511-024-09839-w","DOIUrl":"10.1007/s10511-024-09839-w","url":null,"abstract":"<p>As examples of applying the formulas from part I we examine scattering in a one-dimensional medium for which all the characteristics of the radiative field are expressed in terms of elementary functions and (three-dimensional) isotropic monochromatic scattering. Some properties of the Ambartsumyan function are studied and the asymptotes of the average numbers of photon scattering events in an optically thick plane layer are derived.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"375 - 404"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443242","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
Lorentzian Correction for the Evolution of the CMB Temperature 对 CMB 温度演变的洛伦兹修正
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09837-y
A. Novais, A. L. B. Ribero
{"title":"Lorentzian Correction for the Evolution of the CMB Temperature","authors":"A. Novais,&nbsp;A. L. B. Ribero","doi":"10.1007/s10511-024-09837-y","DOIUrl":"10.1007/s10511-024-09837-y","url":null,"abstract":"<p>Observational evidence consistently shows that the universe is spatially flat and undergoes Lorentzian time dilation as a function of redshift. In combination, such discoveries suggest that a Minkowskian description of cosmology might be technically viable. The thermal evolution that transpires in a conformal spacetime is herein derived. The description is constrained by the energy conservation of a unified cosmic fluid. The resulting model puts forth a Lorentzian correction for the temperature of the CMB as a function of redshift, which improves current data fitting without adding any free parameter. Furthermore, it sheds light upon the early galaxy formation problem: our model predicts up to 0.86 Gyr older objects within the first two billion years of the structure evolution in the universe.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"348 - 363"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443243","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
Plane Symmetric Gravitational Fields in (D+1)-dimensional General Relativity D+1）维广义相对论中的平面对称引力场
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09840-3
R. M. Avagyan, T. A. Petrosyan, A. A. Saharian, G. H. Harutyunyan
{"title":"Plane Symmetric Gravitational Fields in (D+1)-dimensional General Relativity","authors":"R. M. Avagyan,&nbsp;T. A. Petrosyan,&nbsp;A. A. Saharian,&nbsp;G. H. Harutyunyan","doi":"10.1007/s10511-024-09840-3","DOIUrl":"10.1007/s10511-024-09840-3","url":null,"abstract":"<p>We consider plane symmetric gravitational fields within the framework of General Relativity in (D+1)-dimensional spacetime. Two classes of vacuum solutions correspond to higher-dimensional generalizations of the Rindler and Taub spacetimes. The general solutions are presented for a positive and negative cosmological constant as the only source of the gravity. Matching conditions on a planar boundary between two regions with distinct plane symmetric metric tensors are discussed. An example is considered with Rindler and Taub geometries in neighboring half-spaces. As another example, we discuss a finite thickness cosmological constant slab embedded into the Minkowski, Rindler and Taub spacetimes. The corresponding surface energy-momentum tensor is found required for matching the exterior and interior geometries.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"405 - 419"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443246","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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