We investigate the motion of test particles around a spherically symmetric, non-rotating black hole within the framework of quantum gravity, emphasizing the impact of model parameters on particle dynamics. The black hole is characterized by its mass and two dimensionless parameters, and . Using the effective potential method, we analyze the stability of circular orbits and derive analytical expressions for the energy and angular momentum of test particles as functions of the black hole parameters. Additionally, we examine effective forces, determine the innermost stable circular orbits, and numerically integrate the equations of motion to study diverse particle trajectories. Analytical formulas for radial, vertical, and orbital frequencies, as well as the periastron precession frequency, are found from the exploration of epicyclic oscillations close to the equatorial plane. Lastly, we determine the center-of-mass energy for particle collisions close to the black hole horizon. Our results provide insights into the interaction between quantum gravity effects and black hole dynamics, explaining the substantial influence of and on particle motion.
{"title":"Imprints of quantum gravity on periastron precession and trajectories around a black hole","authors":"Asifa Ashraf , Abdelmalek Bouzenada , S.K. Maurya , Farruh Atamurotov , Phongpichit Channuie , Assmaa Abd-Elmonem , Nesreen Sirelkhtam Elmki Abdalla","doi":"10.1016/j.dark.2024.101787","DOIUrl":"10.1016/j.dark.2024.101787","url":null,"abstract":"<div><div>We investigate the motion of test particles around a spherically symmetric, non-rotating black hole within the framework of quantum gravity, emphasizing the impact of model parameters on particle dynamics. The black hole is characterized by its mass <span><math><mi>M</mi></math></span> and two dimensionless parameters, <span><math><mi>α</mi></math></span> and <span><math><mi>β</mi></math></span>. Using the effective potential method, we analyze the stability of circular orbits and derive analytical expressions for the energy and angular momentum of test particles as functions of the black hole parameters. Additionally, we examine effective forces, determine the innermost stable circular orbits, and numerically integrate the equations of motion to study diverse particle trajectories. Analytical formulas for radial, vertical, and orbital frequencies, as well as the periastron precession frequency, are found from the exploration of epicyclic oscillations close to the equatorial plane. Lastly, we determine the center-of-mass energy for particle collisions close to the black hole horizon. Our results provide insights into the interaction between quantum gravity effects and black hole dynamics, explaining the substantial influence of <span><math><mi>α</mi></math></span> and <span><math><mi>β</mi></math></span> on particle motion.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101787"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100680","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2025.101814
Mohammad Ali S. Afshar, Jafar Sadeghi
Non-commutative black holes (NCBH), due to the non-commutativity of spacetime coordinates, lead to a modification of the spacetime metric. By replacing the Dirac delta function with a Gaussian distribution, the mass is effectively smeared, eliminating point-like singularities. Our objective is to investigate the impact of this change on spacetime geodesics, including photon spheres and time-like orbits. We will demonstrate how the photon sphere can serve as a tool to classify spacetime, illustrating the influence of the NC parameter and constraining its values in various modes of these black holes. Additionally, using this classification, we will show how the addition of the nonlinear Einstein–Born–Infeld (BI) field to the model enhances its physical alignment with reality compared to the charged model. In the dS BI model, we will show how the study of the effective potential and photon sphere can provide insights into the initial structural status of the model, thereby establishing this potential as an effective tool for examining the initial conditions of black holes. Finally, by examining super-extremality conditions, we will show that the AdS BI model, with the necessary conditions, can be a suitable candidate for studying and observing the effects of the Weak Gravity Conjecture (WGC).
{"title":"Mutual influence of photon sphere and non-commutative parameter in various non-commutative black holes: Towards evidence for WGC","authors":"Mohammad Ali S. Afshar, Jafar Sadeghi","doi":"10.1016/j.dark.2025.101814","DOIUrl":"10.1016/j.dark.2025.101814","url":null,"abstract":"<div><div>Non-commutative black holes (NCBH), due to the non-commutativity of spacetime coordinates, lead to a modification of the spacetime metric. By replacing the Dirac delta function with a Gaussian distribution, the mass is effectively smeared, eliminating point-like singularities. Our objective is to investigate the impact of this change on spacetime geodesics, including photon spheres and time-like orbits. We will demonstrate how the photon sphere can serve as a tool to classify spacetime, illustrating the influence of the NC parameter and constraining its values in various modes of these black holes. Additionally, using this classification, we will show how the addition of the nonlinear Einstein–Born–Infeld (BI) field to the model enhances its physical alignment with reality compared to the charged model. In the dS BI model, we will show how the study of the effective potential and photon sphere can provide insights into the initial structural status of the model, thereby establishing this potential as an effective tool for examining the initial conditions of black holes. Finally, by examining super-extremality conditions, we will show that the AdS BI model, with the necessary conditions, can be a suitable candidate for studying and observing the effects of the Weak Gravity Conjecture (WGC).</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101814"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100683","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101781
Muhammad Usman , Abdul Jawad , Mohammad Mahtab Alam , Sanjar Shaymatov
Dynamical system analysis is a vital mathematical mechanism for the qualitative study of dynamical models. Cosmological equations governing the dynamics of an isotropic and homogeneous Universe imply dynamical models in the form of differential equations. In the present article, we formulate four models with nonlinear interactions in the theoretical framework of deformed Hořava–Liftshitz and apply the dynamical system analysis to these models to investigate their dynamical stability with phase portraits. Phase portrait trajectories identify the stable steady states for each model, we compute different cosmic parameters at these stable critical points and compare it with the latest observational cosmic data. We find our outcomes are consistent with recent comic observational data, this implies that the theoretical framework under consideration with nonlinear interactions is consistent with current accelerating scenario of the Universe.
{"title":"Effects of nonlinear interactions on phase portraits and dynamical stability in specific modified gravity","authors":"Muhammad Usman , Abdul Jawad , Mohammad Mahtab Alam , Sanjar Shaymatov","doi":"10.1016/j.dark.2024.101781","DOIUrl":"10.1016/j.dark.2024.101781","url":null,"abstract":"<div><div>Dynamical system analysis is a vital mathematical mechanism for the qualitative study of dynamical models. Cosmological equations governing the dynamics of an isotropic and homogeneous Universe imply dynamical models in the form of differential equations. In the present article, we formulate four models with nonlinear interactions in the theoretical framework of deformed Hořava–Liftshitz and apply the dynamical system analysis to these models to investigate their dynamical stability with phase portraits. Phase portrait trajectories identify the stable steady states for each model, we compute different cosmic parameters at these stable critical points and compare it with the latest observational cosmic data. We find our outcomes are consistent with recent comic observational data, this implies that the theoretical framework under consideration with nonlinear interactions is consistent with current accelerating scenario of the Universe.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101781"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143095539","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101769
Diego Tessainer, Antonio L. Maroto, Prado Martín-Moruno
We consider theories which break the invariance under diffeomorphisms (Diff) down to transverse diffeomorphisms (TDiff) in the matter sector, consisting of multiple scalar fields. In particular, we regard shift-symmetric models with two free TDiff scalar fields in a flat Robertson-Walker spacetime (FLRW) and use the perfect fluid approach to study their dynamics. As a consequence of the symmetry breaking, an effective interaction between the fields is induced from the conservation of the total energy–momentum tensor, without the necessity to introduce any explicit interacting term in the Lagrangian. We study the different single-field domination regimes and analyze the energy exchange between the fields. Thereupon, we introduce an application of these models for the description of interactions in the dark sector, and compare the theoretical predictions of our model to observational data from Type Ia supernovae.
{"title":"Multi-field TDiff theories for cosmology","authors":"Diego Tessainer, Antonio L. Maroto, Prado Martín-Moruno","doi":"10.1016/j.dark.2024.101769","DOIUrl":"10.1016/j.dark.2024.101769","url":null,"abstract":"<div><div>We consider theories which break the invariance under diffeomorphisms (Diff) down to transverse diffeomorphisms (TDiff) in the matter sector, consisting of multiple scalar fields. In particular, we regard shift-symmetric models with two free TDiff scalar fields in a flat Robertson-Walker spacetime (FLRW) and use the perfect fluid approach to study their dynamics. As a consequence of the symmetry breaking, an effective interaction between the fields is induced from the conservation of the total energy–momentum tensor, without the necessity to introduce any explicit interacting term in the Lagrangian. We study the different single-field domination regimes and analyze the energy exchange between the fields. Thereupon, we introduce an application of these models for the description of interactions in the dark sector, and compare the theoretical predictions of our model to observational data from Type Ia supernovae.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101769"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143099707","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101764
Jitendra Kumar , Sat Paul , S.K. Maurya , Sourav Chaudhary , Sweeti Kiroriwal
In this work, we investigate an anisotropic compact star’s physical properties and stability in gravity. The study focuses on the significance of gravity on the structure and stability of compact star, considering non-perfect fluid. Buchdahl ansatz along with transformation used to solve the Einstein field equations. We investigate the physical parameters of the 4U1820-30 compact star using a static spherical metric in the interior region and a Schwarzschild (anti) de-sitter metric in the exterior region. We investigate the behaviour of energy density(), radial pressure(), tangential pressure(), anisotropy(), metric potentials, energy state parameter and energy requirements in the interior of the proposed stellar object. The equilibrium state of this star is analysed using the Tolman–Oppenheimer–Volkoff(TOV) equation and their stability is determined using the Necessary and physical existence requirements , causality condition, Harrison-Zeldovich-Novikov condition, the adiabatic index() method and Herrera cracking method.
{"title":"A generalized solution for anisotropic compact star model in F(Q) gravity","authors":"Jitendra Kumar , Sat Paul , S.K. Maurya , Sourav Chaudhary , Sweeti Kiroriwal","doi":"10.1016/j.dark.2024.101764","DOIUrl":"10.1016/j.dark.2024.101764","url":null,"abstract":"<div><div>In this work, we investigate an anisotropic compact star’s physical properties and stability in <span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>Q</mi><mo>)</mo></mrow></mrow></math></span> gravity. The study focuses on the significance of <span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>Q</mi><mo>)</mo></mrow></mrow></math></span> gravity on the structure and stability of compact star, considering non-perfect fluid. Buchdahl ansatz along with transformation used to solve the Einstein field equations. We investigate the physical parameters of the 4U1820-30 compact star using a static spherical metric in the interior region and a Schwarzschild (anti) de-sitter metric in the exterior region. We investigate the behaviour of energy density(<span><math><mi>ρ</mi></math></span>), radial pressure(<span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span>), tangential pressure(<span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>t</mi></mrow></msub></math></span>), anisotropy(<span><math><mi>Δ</mi></math></span>), metric potentials, energy state parameter and energy requirements in the interior of the proposed stellar object. The equilibrium state of this star is analysed using the Tolman–Oppenheimer–Volkoff(TOV) equation and their stability is determined using the Necessary and physical existence requirements , causality condition, Harrison-Zeldovich-Novikov condition, the adiabatic index(<span><math><mi>Γ</mi></math></span>) method and Herrera cracking method.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101764"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100013","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101759
Sai Swagat Mishra , N.S. Kavya , P.K. Sahoo , V. Venkatesha
Cosmography has been extensively utilized to constrain the kinematic state of the Universe using measured distances. In this work, we propose a new method to reconstruct coupling theories using the first kind of Chebyshev polynomial for two variables in which the functional form of the theory has been obtained. Further, the unknowns that appeared in the series are constrained using the cosmographic parameters. We find the explicit form of the luminosity distance in terms of cosmographic parameters to perform MCMC analysis using the PANTHEON＋SH0ES data set. Through the distance modulus function, we observe that the result comes out to be an excellent match to the standard cosmological model and data.
{"title":"Chebyshev cosmography in the framework of extended symmetric teleparallel theory","authors":"Sai Swagat Mishra , N.S. Kavya , P.K. Sahoo , V. Venkatesha","doi":"10.1016/j.dark.2024.101759","DOIUrl":"10.1016/j.dark.2024.101759","url":null,"abstract":"<div><div>Cosmography has been extensively utilized to constrain the kinematic state of the Universe using measured distances. In this work, we propose a new method to reconstruct coupling theories using the first kind of Chebyshev polynomial for two variables in which the functional form of the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> theory has been obtained. Further, the unknowns that appeared in the series are constrained using the cosmographic parameters. We find the explicit form of the luminosity distance in terms of cosmographic parameters to perform MCMC analysis using the PANTHEON＋SH0ES data set. Through the distance modulus function, we observe that the result comes out to be an excellent match to the standard cosmological model and data.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101759"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100017","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101726
M.R. Shahzad , Wajiha Habib , Asifa Ashraf , Faisal Javed , Awatef Abidi , Maha Alammari , Ali M. Mubaraki
<div><div>In this paper, we proposed a new mathematical model of charged isotropic compact relativistic object in the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity. In the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> framework, the gravitational action involves the trace of the energy–momentum tensor <span><math><mi>T</mi></math></span> and the Ricci scalar <span><math><mi>R</mi></math></span>. We choose a specific <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> framework such that <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>χ</mi><mi>T</mi></mrow></math></span>, in which <span><math><mi>χ</mi></math></span> represents the coupling parameter, which is responsible for measuring the deviation from the standard Einstein’s general theory of relativity (GR). A short overview of the modified <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity theory is presented and the field equations are formulated in this novel modified gravity. It is shown that for a specific limit of the coupling parameter, the standard <span><math><mrow><mi>G</mi><mi>R</mi></mrow></math></span> can be restored from the considered <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> model. We modeled, mathematically, a specific charged compact star <span><math><mrow><mi>X</mi><mi>T</mi><mi>E</mi><mi>J</mi><mn>1739</mn><mo>−</mo><mn>217</mn></mrow></math></span> (M=1.51<span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub></math></span>, R=10.9 km), within the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> extended gravity theory framework by taking benefit from the well studied Heintzmann IIa ansatz [H. Heintzmann, Z. Physik 228, 489–493 (1969)]. To examine the reliability and physical plausibility of Our model, different physical characteristics such as the energy density and pressure, electric field, energy conditions, stability analysis via Herrara cracking technique and the adiabatic index, equilibrium conditions under different forces, mass–radius relationship, compactness and surface red-shift are studied carefully, which are essential for confirming the model’s physical feasibility. The mathematically established results are more accurately represented by graphical illustrations for the various chosen values of the coupling parameter <span><math><mi>χ</mi></math></span>. In this study, we also compared our findings with the standard GR results and the observational facts, and we inferred that for nonzero values of the coupling parameter, <span><math><mi>χ</mi></math></span
{"title":"General isotropic charged fluid spheres within the matter coupling gravity formalism","authors":"M.R. Shahzad , Wajiha Habib , Asifa Ashraf , Faisal Javed , Awatef Abidi , Maha Alammari , Ali M. Mubaraki","doi":"10.1016/j.dark.2024.101726","DOIUrl":"10.1016/j.dark.2024.101726","url":null,"abstract":"<div><div>In this paper, we proposed a new mathematical model of charged isotropic compact relativistic object in the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity. In the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> framework, the gravitational action involves the trace of the energy–momentum tensor <span><math><mi>T</mi></math></span> and the Ricci scalar <span><math><mi>R</mi></math></span>. We choose a specific <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> framework such that <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>χ</mi><mi>T</mi></mrow></math></span>, in which <span><math><mi>χ</mi></math></span> represents the coupling parameter, which is responsible for measuring the deviation from the standard Einstein’s general theory of relativity (GR). A short overview of the modified <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> gravity theory is presented and the field equations are formulated in this novel modified gravity. It is shown that for a specific limit of the coupling parameter, the standard <span><math><mrow><mi>G</mi><mi>R</mi></mrow></math></span> can be restored from the considered <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> model. We modeled, mathematically, a specific charged compact star <span><math><mrow><mi>X</mi><mi>T</mi><mi>E</mi><mi>J</mi><mn>1739</mn><mo>−</mo><mn>217</mn></mrow></math></span> (M=1.51<span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⨀</mo></mrow></msub></math></span>, R=10.9 km), within the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> extended gravity theory framework by taking benefit from the well studied Heintzmann IIa ansatz [H. Heintzmann, Z. Physik 228, 489–493 (1969)]. To examine the reliability and physical plausibility of Our model, different physical characteristics such as the energy density and pressure, electric field, energy conditions, stability analysis via Herrara cracking technique and the adiabatic index, equilibrium conditions under different forces, mass–radius relationship, compactness and surface red-shift are studied carefully, which are essential for confirming the model’s physical feasibility. The mathematically established results are more accurately represented by graphical illustrations for the various chosen values of the coupling parameter <span><math><mi>χ</mi></math></span>. In this study, we also compared our findings with the standard GR results and the observational facts, and we inferred that for nonzero values of the coupling parameter, <span><math><mi>χ</mi></math></span","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101726"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100058","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}
Pub Date : 2025-02-01DOI: 10.1016/j.dark.2024.101783
Tayyab Naseer , M. Sharif , Fatima Chand
In the framework of theory, this paper develops two unique non-singular interior models that describe anisotropic spherical structures in the presence of an electromagnetic field. The modified Einstein–Maxwell field equations are formulated in conjunction with a static charged interior geometry. After that, the field equations are solved by applying two distinct forms of the radial metric potential that make the system easier to solve. Using particular types of anisotropic pressure, we obtain two different models. We come across differential equations in both cases, and their solutions contain constants of integration which are found through matching conditions of an inner and the outer Reissner–Nordström line elements at the spherical boundary. In this context, the assumption of zero radial pressure at the interface is also utilized. Next, we investigate certain conditions that, when satisfied, result in physically existing compact models. We consider the observed data of a star, LMC X-4, together with several parametric values in order to graphically evaluate the developed solutions. Our results show that, for chosen values of charge andmodel parameter, both models fit the physically existing conditions in this modified theory.
{"title":"Imprints of electric charge on the stability of compact stellar models: A comparison between GR and f(R,T) gravity","authors":"Tayyab Naseer , M. Sharif , Fatima Chand","doi":"10.1016/j.dark.2024.101783","DOIUrl":"10.1016/j.dark.2024.101783","url":null,"abstract":"<div><div>In the framework 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, this paper develops two unique non-singular interior models that describe anisotropic spherical structures in the presence of an electromagnetic field. The modified Einstein–Maxwell field equations are formulated in conjunction with a static charged interior geometry. After that, the field equations are solved by applying two distinct forms of the radial metric potential that make the system easier to solve. Using particular types of anisotropic pressure, we obtain two different models. We come across differential equations in both cases, and their solutions contain constants of integration which are found through matching conditions of an inner and the outer Reissner–Nordström line elements at the spherical boundary. In this context, the assumption of zero radial pressure at the interface is also utilized. Next, we investigate certain conditions that, when satisfied, result in physically existing compact models. We consider the observed data of a star, LMC X-4, together with several parametric values in order to graphically evaluate the developed solutions. Our results show that, for chosen values of charge andmodel parameter, both models fit the physically existing conditions in this modified theory.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101783"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100221","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}
This article explores the motion of massive particles in the gravitational field of a modified gravity (MOG) black hole (BH), characterized by the parameter . Using the Hamiltonian formalism, the geodesic equations and the effective potential governing particle trajectories are derived. Key features, including the innermost stable circular orbit (ISCO) and the innermost bound circular orbit (IBCO), are analyzed, revealing their dependence on the particle’s energy, angular momentum, and the MOG parameter. In the extremal case, where , the event horizon merges with the Cauchy horizon, forming a distinctive BH configuration. Numerical methods are employed to compute periodic orbits in this spacetime, with a comparison drawn to the Schwarzschild BH. The findings indicate that for , periodic orbits around Schwarzschild-MOG BH exhibit lower energy requirements than those in Schwarzschild spacetime, whereas for , the energy requirements are higher. Precessing orbits near periodic trajectories are also examined, offering insights into their complex dynamical behavior. Finally, the gravitational wave (GW) radiation from the periodic orbits of a test particle around the Schwarzschild-MOG BH is examined, generating intricate waveforms that provide insights into the gravitational structure of the system.
{"title":"Periodic orbits and their gravitational wave radiations around the Schwarzschild-MOG black hole","authors":"Oreeda Shabbir , Mubasher Jamil , Mustapha Azreg-Aïnou","doi":"10.1016/j.dark.2025.101816","DOIUrl":"10.1016/j.dark.2025.101816","url":null,"abstract":"<div><div>This article explores the motion of massive particles in the gravitational field of a modified gravity (MOG) black hole (BH), characterized by the parameter <span><math><mi>α</mi></math></span>. Using the Hamiltonian formalism, the geodesic equations and the effective potential governing particle trajectories are derived. Key features, including the innermost stable circular orbit (ISCO) and the innermost bound circular orbit (IBCO), are analyzed, revealing their dependence on the particle’s energy, angular momentum, and the MOG parameter. In the extremal case, where <span><math><mrow><mi>α</mi><mo>=</mo><mo>−</mo><mn>1</mn></mrow></math></span>, the event horizon merges with the Cauchy horizon, forming a distinctive BH configuration. Numerical methods are employed to compute periodic orbits in this spacetime, with a comparison drawn to the Schwarzschild BH. The findings indicate that for <span><math><mrow><mi>α</mi><mo>></mo><mn>0</mn></mrow></math></span>, periodic orbits around Schwarzschild-MOG BH exhibit lower energy requirements than those in Schwarzschild spacetime, whereas for <span><math><mrow><mo>−</mo><mn>1</mn><mo><</mo><mi>α</mi><mo><</mo><mn>0</mn></mrow></math></span>, the energy requirements are higher. Precessing orbits near periodic trajectories are also examined, offering insights into their complex dynamical behavior. Finally, the gravitational wave (GW) radiation from the periodic orbits of a test particle around the Schwarzschild-MOG BH is examined, generating intricate waveforms that provide insights into the gravitational structure of the system.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101816"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100686","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}
In this study, we explore generalized Ellis–Bronnikov and embedded wormhole solutions within the context of gravity with an anisotropic matter source. To achieve the necessary conditions for wormhole formation, we investigate the energy conditions within gravity. Our analysis includes various matter distributions, particularly dark matter halos, using observational data from the galaxy. We also explore the results in the framework of gravity, considering three different dark matter halo distributions. For each case, the violation of energy conditions proves the presence of strange matter, say exotic matter, which is a necessary condition for wormhole existence in this gravitational model when dark matter halos are present. We investigate the effect of physical parameters on the stable configurations of the generated thin-shell surrounding the wormhole structure. In the first scenario, we can see that the shape function parameters have a significant impact on the shell’s stable regions. In addition, the considered black hole contributes significantly to the shell’s stability.
{"title":"Construction of wormhole under embedded approach through dark matter halos in F(T,TG) gravity","authors":"Asifa Ashraf , Wen-Xiu Ma , Faisal Javed , S.K. Maurya , Farruh Atamurotov , Abdelmalek Bouzenada , Magda Abd El-Rahman","doi":"10.1016/j.dark.2024.101777","DOIUrl":"10.1016/j.dark.2024.101777","url":null,"abstract":"<div><div>In this study, we explore generalized Ellis–Bronnikov and embedded wormhole solutions within the context of <span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>T</mi><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>G</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> gravity with an anisotropic matter source. To achieve the necessary conditions for wormhole formation, we investigate the energy conditions within <span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>T</mi><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>G</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> gravity. Our analysis includes various matter distributions, particularly dark matter halos, using observational data from the <span><math><mrow><mi>M</mi><mn>87</mn></mrow></math></span> galaxy. We also explore the results in the framework of <span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>T</mi><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>G</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> gravity, considering three different dark matter halo distributions. For each case, the violation of energy conditions proves the presence of strange matter, say exotic matter, which is a necessary condition for wormhole existence in this gravitational model when dark matter halos are present. We investigate the effect of physical parameters on the stable configurations of the generated thin-shell surrounding the wormhole structure. In the first scenario, we can see that the shape function parameters have a significant impact on the shell’s stable regions. In addition, the considered black hole contributes significantly to the shell’s stability.</div></div>","PeriodicalId":48774,"journal":{"name":"Physics of the Dark Universe","volume":"47 ","pages":"Article 101777"},"PeriodicalIF":5.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143099710","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}
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