Physics of the Dark Universe最新文献

{"title":"Particle dynamics and Joule–Thomson expansion of phantom anti-de Sitter black hole stability and thermal fluctuations in massive gravity","authors":"Faisal Javed ,&nbsp;Arfa Waseem ,&nbsp;Phongpichit Channuie ,&nbsp;G. Mustafa ,&nbsp;Taseer Muhammad ,&nbsp;Ertan Güdekli","doi":"10.1016/j.dark.2024.101766","DOIUrl":"10.1016/j.dark.2024.101766","url":null,"abstract":"<div><div>This study delves into the dynamics of phantom anti-de Sitter black holes within a massive gravity framework, providing a comprehensive examination of the interplay between thermodynamic principles and gravitational dynamics. We investigate Joule-Thomson expansions and their implications for black hole thermodynamics, revealing how variations in temperature and pressure affect gas behavior relative to the horizon radius. Our analysis of the Joule-Thomson coefficients shows that smaller black holes exhibit positive coefficients indicative of gas expansion during cooling, while larger black holes display negative coefficients associated with heating behaviors. We further explore the corrected entropy of black holes, noting oscillations in smaller charged black holes that stabilize with larger horizon radii, while phantom energy configurations exhibit significant differences in stability characteristics. Our assessment of Helmholtz free energy, internal energy, enthalpy, and Gibbs free energy highlights contrasting stability trends between charged and phantom-AdS black holes, with the former displaying stable thermodynamic properties and the latter indicating increased instability at low charges and horizon radii. Additionally, the analysis of effective potential dynamics reveals critical insights into the stability of the innermost stable circular orbits for test particles. We demonstrate that the innermost stable circular orbit behavior in both charged and phantom-AdS black holes is significantly influenced by parameters <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, illustrating the complex relationship between black hole properties and orbital dynamics. In summary, our findings elucidate the intricate relationship between thermodynamics and gravitational behavior in black hole systems, particularly regarding the unique effects of phantom energy.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101766"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143155697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Unified description of dark energy and dark matter candidates with the dark energy interiors","authors":"Irina Dymnikova","doi":"10.1016/j.dark.2024.101738","DOIUrl":"10.1016/j.dark.2024.101738","url":null,"abstract":"<div><div>We overview the systematic approach to the unified description of dark energy (DE) and a certain class of dark matter (DM) candidates represented by stress–energy tensors with the algebraic structure <span><math><mrow><msubsup><mrow><mi>T</mi></mrow><mrow><mi>t</mi></mrow><mrow><mi>t</mi></mrow></msubsup><mo>=</mo><msubsup><mrow><mi>T</mi></mrow><mrow><mi>r</mi></mrow><mrow><mi>r</mi></mrow></msubsup></mrow></math></span>, qualified as a vacuum dark fluid. Most of the relevant solutions to the Einstein equations presented in the literature satisfy this condition. Regular solutions describe spacetimes with the non-zero background cosmological constant and de Sitter center surrounded by intrinsically anisotropic <span><math><mi>r</mi></math></span>-dependent quintessence. Dependently on the choice of the reference frame, they describe the Lemaître class cosmological models with the initial and final de Sitter stages, and regular compact objects with the de Sitter centers. For a special class of Lemaître cosmological models the universe evolution is guided by the quantum evaporation of the cosmological horizon, which uniquely determines the non-zero final value of the vacuum energy density <span><math><msub><mrow><mi>ρ</mi></mrow><mrow><mi>v</mi><mi>a</mi><mi>c</mi></mrow></msub></math></span>. Regular compact objects with the de Sitter centers include regular black holes, their remnants, whose existence is supported by spacetime symmetry, and self-gravitating solitons G-lumps replacing naked singularities. For a special class of regular rotating compact objects distinguished by the energy conditions, interiors contain regions of anisotropic <span><math><mi>r</mi></math></span>-dependent phantom fluid. Regular primordial black holes, their remnants and G-lumps can be qualified as heavy DM candidates with DE interiors. Their observational signatures provide information about the matter content of their interiors.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101738"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143156718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Kinetic coupled tachyon: A dynamical system analysis","authors":"Francesco Pace ,&nbsp;Alberto Rozas-Fernández ,&nbsp;Özgen Tunç Türker","doi":"10.1016/j.dark.2024.101786","DOIUrl":"10.1016/j.dark.2024.101786","url":null,"abstract":"<div><div>We present and examine a kinetically coupled tachyon dark energy model, where a tachyon scalar field <span><math><mi>ϕ</mi></math></span> interacts with the matter sector. More specifically, we deduce this cosmological setting from a generalised interacting dark energy model that allows for the kinetic term of the scalar field to couple to the matter species <em>a priori</em> in the action. A thorough dynamical system analysis and its cosmological implications unveil the appearance of a scaling solution which is also an attractor of the system, thanks to a novel critical point, with a period of accelerated expansion thereafter. This new solution, not present in the uncoupled case, has the enticing consequence of alleviating the coincidence problem.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101786"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Impact of spatial curvature on forecast constraints from standard and differential redshift drift measurements","authors":"C.J.A.P. Martins ,&nbsp;M.A.F. Melo e Sousa ,&nbsp;S.Q. Fernandes ,&nbsp;C.M.J. Marques","doi":"10.1016/j.dark.2024.101775","DOIUrl":"10.1016/j.dark.2024.101775","url":null,"abstract":"<div><div>The redshift drift of objects following the cosmological expansion is a unique model-independent probe of background cosmology, detectable by astrophysical facilities presently under construction. Previous forecasts for such measurements assume flat universes. We explore the impact of relaxing this assumption on the constraining power of the redshift drift, focusing on the two most promising routes for its measurement: the SKA at low redshifts, and the Golden Sample for the ELT’s ANDES spectrograph at higher redshifts. We also discuss the cosmological sensitivity of possible differential redshift drift measurements, both on their own and, for the specific case of the Golden Sample, in combination with the standard method. Overall, we find that the sensitivity of the redshift drift to curvature is comparable to that of matter (especially at low redshifts) and higher than the sensitivity to the dark energy equation of state. We also show that the sensitivity of redshift drift measurements to these cosmological parameters is asymmetric with respect to the curvature parameter, being different for open and closed universes with the same absolute value of the curvature parameter <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>k</mi></mrow></msub></math></span>.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101775"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143099726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Self bound compact stars in f(R,T) gravity admitting CFL equation of state in presence of non-minimal QCD correction factor","authors":"Koushik Ballav Goswami ,&nbsp;Debadri Bhattacharjee ,&nbsp;Pradip Kumar Chattopadhyay ,&nbsp;Anirban Saha","doi":"10.1016/j.dark.2024.101752","DOIUrl":"10.1016/j.dark.2024.101752","url":null,"abstract":"<div><div>The present article illustrates a method of generating exact solution for a class of isotropic compact objects in the context of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> theory of gravity based on a linear form of the function <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> as <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo>=</mo><mi>R</mi><mo>+</mo><mn>2</mn><mi>β</mi><mi>T</mi></mrow></math></span>. The internal matter is assumed to be de-confined quarks described by a colour flavour locked (<span><math><mrow><mi>C</mi><mi>F</mi><mi>L</mi></mrow></math></span>) equation of state. To obtain exact solution of the field equations, a specific ansatz has been assumed for the <span><math><msub><mrow><mi>g</mi></mrow><mrow><mi>r</mi><mi>r</mi></mrow></msub></math></span> metric component as proposed by Vaidya and Tikekar. This type of metric ansatz generally describes the interior space–time geometry of a compact object to be 3-spheroid in nature which is embedded in a four dimensional Euclidean flat space. The equation of state in <span><math><mrow><mi>C</mi><mi>F</mi><mi>L</mi></mrow></math></span> phase has been modified by introducing a <span><math><mrow><mi>Q</mi><mi>C</mi><mi>D</mi></mrow></math></span> correction term <span><math><msub><mrow><mi>c</mi></mrow><mrow><mi>c</mi><mi>o</mi><mi>r</mi></mrow></msub></math></span> which has significant effects on the equation of state and energy per baryon of quark matter. The <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> theory and <span><math><mrow><mi>C</mi><mi>F</mi><mi>L</mi></mrow></math></span> phase equation state permit our model to adopt a wider class of compact objects such as EXO 1745-248, LMC X-4, PSR J0740+6620 etc. The observed radii of these compact objects agree with those obtained from our model. The radius of the recently detected binary neutron star merger event GW 230529<span><math><msub><mrow></mrow><mrow><mo>−</mo></mrow></msub></math></span>181500 having mass 3.6 <span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span> can also be predicted from our model.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101752"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Spinor adjoints, gauge invariance and a new road to sterile neutrinos","authors":"R.J. Bueno Rogerio ,&nbsp;G.B. de Gracia","doi":"10.1016/j.dark.2024.101801","DOIUrl":"10.1016/j.dark.2024.101801","url":null,"abstract":"<div><div>In this work, we analyze the possibilities of certain gauge transformations regarding some specific spinorial dual structures. To this end, we define a general structure, which can be expressed in terms of discrete symmetry operators associated with parity, charge conjugation, and time reversal. To this end, we consider the demand of tensor covariance of the spinor bilinears under space–time transformations and also deep algebraic considerations such as the invertibility of the dual structure which guarantee that the physical information remains unchanged (respecting the Fierz–Pauli–Kofink identities), and so on. Later, we examine the global gauge freedom implied by each choice of dual and point out the physical implications. The final goal is achieved by establishing a well-defined coupling between the Elko and standard model neutrinos in a prelude for a new formulation of the hypothetical so-called sterile neutrino.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101801"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Main sequence of star formation and colour bimodality considering galaxy environment","authors":"Pius Privatus ,&nbsp;Umananda Dev Goswami","doi":"10.1016/j.dark.2024.101802","DOIUrl":"10.1016/j.dark.2024.101802","url":null,"abstract":"<div><div>This study involves the use of friend-of-friend method on the volume limited samples constructed from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) to classify the galaxies into isolated and non-isolated environments hence to investigate the influence of the galaxy environment on the main sequence of star formation, and colour bimodality. We classified the galaxies into the luminous volume-limited sample with <span><math><mrow><mo>−</mo><mn>22</mn><mo>.</mo><mn>5</mn><mo>≤</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>≤</mo><mo>−</mo><mn>20</mn><mo>.</mo><mn>5</mn></mrow></math></span> (mag), and the faint volume-limited sample with <span><math><mrow><mo>−</mo><mn>20</mn><mo>.</mo><mn>5</mn><mo>≤</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>≤</mo><mo>−</mo><mn>18</mn><mo>.</mo><mn>5</mn></mrow></math></span> (mag). Using the WHAN diagnostic diagram we assigned the samples into star-forming, strong AGN, weak AGN, and retired galaxies based on their environment (isolated and non-isolated). The friend-of-friend method was successful in producing consistent results regarding the stellar mass-SFR and stellar mass-colour known relations. Apart from that the decrease in the slope of the main sequence for star-forming galaxies by 0.04 dex and intercept by 0.39 dex for the luminous sample was observed while the faint sample a decrease of 0.08 dex in slope and 0.74 dex in intercept was observed between isolated and non-isolated galaxies. A significant difference on the number of galaxies between isolated and non-isolated galaxies within, above and below the main sequence by 7.47%, 28.51%, 14.59% for the luminous sample while for the faint sample by 16.15%, 32.60%, 35.23% on average, respectively are observed. A significant difference in the number of galaxies in the blue cloud, green valley, and red sequence by 10.30%, 20.61%, 5.74% for luminous sample while for faint sample by 28.46%, 41.36%, 8.95% on average, respectively was observed. The study concludes that the galaxy environment influences the shaping and positioning of galaxies along the star formation main sequence and colour bimodality.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101802"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Cosmic and thermodynamics consequences of Chaplygin–Jacobi corrected HDE model","authors":"Nadeem Azhar ,&nbsp;Shamaila Rani ,&nbsp;Abdul Jawad ,&nbsp;Mohammad Mahtab Alam ,&nbsp;Sanjar Shaymatov","doi":"10.1016/j.dark.2025.101819","DOIUrl":"10.1016/j.dark.2025.101819","url":null,"abstract":"<div><div>In this study, we investigate a cosmologically compatible model of the universe using the generalized Chaplygin–Jacobi gas framework. The holographic generalized Chaplygin–Jacobi gas model presents an advanced approach to analyzing dark energy behavior and its role in cosmic evolution. This model brings together ideas from holographic dark energy, generalized Chaplygin gas and Jacobi gas theories. We assume that dark energy sources can be described as generalized Chaplygin–Jacobi gas, associating the Hubble horizon with the Chaplygin scalar field and incorporating specific elliptic identities. In this context, we explore the equation of state parameter, <span><math><mrow><mi>ω</mi><mo>−</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math></span> plane and <span><math><mrow><mi>O</mi><mi>m</mi></mrow></math></span> diagnostics. To assess model stability, we analyze the squared speed of sound and examine the validity of the generalized second law of thermodynamics/thermal condition. Additionally, we evaluate the model’s energy density and pressure to compare its correspondence with the Chaplygin scalar field model. Overall, our findings suggest that the constraints align well with current observational data.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101819"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Modeling of compact stars in de Rham–Gabadadze–Tolley like massive gravity","authors":"M.R. Shahzad ,&nbsp;Wajiha Habib ,&nbsp;Asifa Ashraf ,&nbsp;Awatef Abidi ,&nbsp;H. Elhosiny Ali ,&nbsp;Ali M. Mubaraki","doi":"10.1016/j.dark.2024.101797","DOIUrl":"10.1016/j.dark.2024.101797","url":null,"abstract":"<div><div>We proposed a new mathematical model of compact structure and analyzed the stability in the de Rham Gabadadze Tolley (dRGT) theory of gravity. The formulation of field equations within the framework of the modified theory is presented by considering the anisotropic matter distribution within the spherically symmetric geometry. We employed the Krori and Barua (KB) metric, denoted as <span><math><mrow><mi>ϕ</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><mi>B</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>+</mo><mi>d</mi></mrow></math></span> and <span><math><mrow><mi>λ</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><mi>A</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>, where <span><math><mi>A</mi></math></span>, <span><math><mi>B</mi></math></span>, and <span><math><mi>C</mi></math></span> represent the unknown constants to generate the solution of field equations. In this investigation, we considered five different known compact stars: Vela X-12 with mass 1.77<span><math><mrow><mi>M</mi><mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub><mo>)</mo></mrow></mrow></math></span> and radius 9.99 km, 4U 1608-52 with mass 1.74<span><math><mrow><mi>M</mi><mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub><mo>)</mo></mrow></mrow></math></span> and radius 9.3 km, PSR J1903+327 with mass 1.667<span><math><mrow><mi>M</mi><mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub><mo>)</mo></mrow></mrow></math></span> and radius 9.438 km, Cen X-3 with mass 1.49<span><math><mrow><mi>M</mi><mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub><mo>)</mo></mrow></mrow></math></span> and radius 9.51 km, and 4U 1820-30 with mass 1.58<span><math><mrow><mi>M</mi><mrow><mo>(</mo><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub><mo>)</mo></mrow></mrow></math></span> and radius 9.1 km, respectively to observe the physical properties of the presented model. We have checked our model for physical validity and stability by exploring the graphical behavior of some important properties such as energy density, pressure (P_r, P_t), energy conditions, stability via Herrera cracking concept and the adiabatic index, mass function, compactness, and surface redshift on various compact stars considered in this study. Significantly, we analyzed the demeanor of different forces influenced on the system and observed that our model remain in the hydrostatic equilibrium under the impact of these forces. All the obtained results show that our proposed model is realistic and stable.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101797"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143099728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Spherically symmetric perfect fluid filled universe within the 4 dimensional Einstein–Gauss–Bonnet gravity formalism with vanishing conformal curvature","authors":"Sudan Hansraj ,&nbsp;Chevarra Hansraj ,&nbsp;Njabulo Mkhize ,&nbsp;Abdelghani Errehymy ,&nbsp;Sunil Kumar Maurya","doi":"10.1016/j.dark.2024.101757","DOIUrl":"10.1016/j.dark.2024.101757","url":null,"abstract":"<div><div>Conformally flat spacetime geometry is of immense physical importance. In this context we obtain the most general solutions for 4 dimensional Einstein–Gauss–Bonnet (4D EGB) static spherically symmetric spacetimes. The standard Schwarzschild incompressible fluid sphere is one possible solution, however, new branches of solutions emerge that have cosmological significance. It is intriguing that the geometry of the new model is given by an exactly known spatially directed potential while the remaining potential is given as an integral. It is not necessary to know the explicit form of the temporally directed potential to analyze the physics of the model. However, at least two explicit exact solutions for both potentials are exhibited. Graphical plots are constructed to show that barring a short interval from the center of the distribution which may be excised and replaced with a well-behaved fluid, all the elementary physical tests are successful. The model considered does not admit a finite radius hence is not applicable to astrophysical compact objects however the pleasing physical characteristics of the fluid suggests applicability to a perfect fluid filled universe. The model satisfies the causality requirement preventing the sound speed from becoming superluminal as well as the Chandrasekar stability criterion demanded of adiabatic fluids. Moreover all the energy conditions are complied with. The analysis effectively rules out the existence of conformally flat stars in 4D EGB gravity aside from the interior Schwarzschild spacetime.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101757"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}