Pub Date : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117325
Vipul Kumar Pandey , Ronaldo Thibes
Finite-field-dependent-Becchi-Rouet-Stora-Tyutin (FFBRST) transformations, as proposed by Joglekar and Mandal, generalize the usual BRST ones by allowing the corresponding anti-commuting parameter to be finite and field-dependent and can be used to connect Green functions in different gauges. In this work, we approach the gauge-invariant Siegel-Zwiebach (SZ) action obtained from the bosonic string in the critical dimension in different classes of gauge-fixings and perform their explicit connection in terms of FFBRST transformations. BRST symmetry is preserved. As important particular cases, we discuss and contextualize the Fierz-Pauli (FP) massive and massless actions describing linearized gravity and show how the massive graviton propagator can smoothly converge to the massless case in a transverse-traceless gauge, shedding light on the vanDam-Veltman-Zakharov discontinuity.
{"title":"Connecting Green’s functions in the Siegel-Zwiebach model through FFBRST transformations","authors":"Vipul Kumar Pandey , Ronaldo Thibes","doi":"10.1016/j.nuclphysb.2026.117325","DOIUrl":"10.1016/j.nuclphysb.2026.117325","url":null,"abstract":"<div><div>Finite-field-dependent-Becchi-Rouet-Stora-Tyutin (FFBRST) transformations, as proposed by Joglekar and Mandal, generalize the usual BRST ones by allowing the corresponding anti-commuting parameter to be finite and field-dependent and can be used to connect Green functions in different gauges. In this work, we approach the gauge-invariant Siegel-Zwiebach (SZ) action obtained from the bosonic string in the critical dimension in different classes of gauge-fixings and perform their explicit connection in terms of FFBRST transformations. BRST symmetry is preserved. As important particular cases, we discuss and contextualize the Fierz-Pauli (FP) massive and massless actions describing linearized gravity and show how the massive graviton propagator can smoothly converge to the massless case in a transverse-traceless gauge, shedding light on the vanDam-Veltman-Zakharov discontinuity.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117325"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117328
L.A.S. Evangelista, A.F. Santos
We investigate the gravitational scattering process within the framework of gravitoelectromagnetism, a weak-field approximation of gravity analogous to Maxwell’s theory of electromagnetism. This process involves the interaction between a fermion and an antifermion mediated by graviton exchange. We consider the nonminimal gravitational sector of the standard model extension and calculate the corrections to the scattering cross section arising from Lorentz violation. The analysis is carried out in two scenarios: (i) at zero temperature and (ii) at finite temperature. To incorporate thermal effects, we employ the thermo field dynamics formalism, which allows for a consistent treatment of quantum fields at finite temperature. The results provide insights into how Lorentz-violating and thermal corrections influence gravitational interactions, particularly relevant in high-energy or astrophysical environments.
我们在引力电磁学框架下研究了引力e−+e+→r−+ r +散射过程，引力电磁学是一种类似于麦克斯韦电磁学理论的引力弱场近似。这个过程涉及费米子和反费米子之间的相互作用，由引力子交换介导。我们考虑了标准模型扩展的非极小引力扇区，并计算了由洛伦兹破坏引起的散射截面的修正。分析在两种情况下进行：(i)在零温度和（ii）在有限温度下。为了结合热效应，我们采用热场动力学形式，它允许在有限温度下对量子场进行一致的处理。结果提供了洛伦兹违反和热修正如何影响引力相互作用的见解，特别是在高能或天体物理环境中。
{"title":"Gravitational Lorentz-violating e−+e+→ℓ−+ℓ+ scattering","authors":"L.A.S. Evangelista, A.F. Santos","doi":"10.1016/j.nuclphysb.2026.117328","DOIUrl":"10.1016/j.nuclphysb.2026.117328","url":null,"abstract":"<div><div>We investigate the gravitational <span><math><mrow><msup><mi>e</mi><mo>−</mo></msup><mo>+</mo><msup><mi>e</mi><mo>+</mo></msup><mo>→</mo><msup><mi>ℓ</mi><mo>−</mo></msup><mo>+</mo><msup><mi>ℓ</mi><mo>+</mo></msup></mrow></math></span> scattering process within the framework of gravitoelectromagnetism, a weak-field approximation of gravity analogous to Maxwell’s theory of electromagnetism. This process involves the interaction between a fermion and an antifermion mediated by graviton exchange. We consider the nonminimal gravitational sector of the standard model extension and calculate the corrections to the scattering cross section arising from Lorentz violation. The analysis is carried out in two scenarios: (i) at zero temperature and (ii) at finite temperature. To incorporate thermal effects, we employ the thermo field dynamics formalism, which allows for a consistent treatment of quantum fields at finite temperature. The results provide insights into how Lorentz-violating and thermal corrections influence gravitational interactions, particularly relevant in high-energy or astrophysical environments.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117328"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117322
Yu-Pan Zeng
We propose a new kind of Dark Matter: Derivative Portal Dark Matter. This kind of Dark Matter connects to the Standard Model through a massive mediator, which links to the Standard Model in derivative form. The derivative of a mediator in momentum space corresponds to the mediated momentum, which vanishes in the zero momentum transfer limit. As a result, this kind of Dark Matter can evade stringent constraint from the Dark Matter direct detection while fitting the Dark Matter relic density observation naturally. We explore several UV complete models of this kind of Dark matter. What’s more, we show that these models also survive from Dark Matter indirect detection and collider search.
{"title":"Derivative portal dark matter","authors":"Yu-Pan Zeng","doi":"10.1016/j.nuclphysb.2026.117322","DOIUrl":"10.1016/j.nuclphysb.2026.117322","url":null,"abstract":"<div><div>We propose a new kind of Dark Matter: Derivative Portal Dark Matter. This kind of Dark Matter connects to the Standard Model through a massive mediator, which links to the Standard Model in derivative form. The derivative of a mediator in momentum space corresponds to the mediated momentum, which vanishes in the zero momentum transfer limit. As a result, this kind of Dark Matter can evade stringent constraint from the Dark Matter direct detection while fitting the Dark Matter relic density observation naturally. We explore several UV complete models of this kind of Dark matter. What’s more, we show that these models also survive from Dark Matter indirect detection and collider search.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117322"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117321
Hernando Quevedo , María N. Quevedo
We study the thermodynamic properties of black holes, taking into account the non-extensive character of their entropy at the thermodynamic and statistical level. To this end, we assume that the Rényi entropy determines the fundamental thermodynamic equation of black holes and is represented by a quasi-homogeneous function. As a consequence, the Rényi parameter turns out to be an independent thermodynamic variable, which must be treated in the framework of extended thermodynamics. As a particular example, we use the formalism of geometrothermodynamics to show that the Schwarzschild black hole can become stable for certain values of the Rényi parameter.
{"title":"Non-extensive and quasi-homogeneous geometrothermodynamics","authors":"Hernando Quevedo , María N. Quevedo","doi":"10.1016/j.nuclphysb.2026.117321","DOIUrl":"10.1016/j.nuclphysb.2026.117321","url":null,"abstract":"<div><div>We study the thermodynamic properties of black holes, taking into account the non-extensive character of their entropy at the thermodynamic and statistical level. To this end, we assume that the Rényi entropy determines the fundamental thermodynamic equation of black holes and is represented by a quasi-homogeneous function. As a consequence, the Rényi parameter turns out to be an independent thermodynamic variable, which must be treated in the framework of extended thermodynamics. As a particular example, we use the formalism of geometrothermodynamics to show that the Schwarzschild black hole can become stable for certain values of the Rényi parameter.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117321"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
We investigate the dynamics of charged spinning test particles in the spacetime of a magnetized Bocharova-Bronnikov-Melnikov-Bekenstein black hole (BH), an extremal solution of the Einstein-Maxwell-conformally coupled scalar field equations. Using the Mathisson-Papapetrou-Dixon equations, we derive the equations of motion that incorporate spin-curvature coupling and electromagnetic interactions due to the particle’s charge and an external magnetic field. The effective potential formalism is employed to analyze stable circular orbits, the innermost stable circular orbit (ISCO), and the superluminal bound, ensuring timelike motion. The influence of the particle’s spin s, a magnetic coupling parameter ωB, is examined numerically, revealing significant shifts in the ISCO radius, specific angular momentum, and energy due to spin and electromagnetic effects. We further study particle collisions near the event horizon, computing the critical angular momentum and center-of-mass energy, which exhibit enhancements akin to the Bañados-Silk-West effect, driven by gravitational, electromagnetic, and spin interactions. Our results highlight the intricate interplay of these effects in the BBMB spacetime, offering insights into high-energy astrophysical processes such as accretion disk dynamics and particle acceleration near magnetized BHs.
{"title":"Spin effects on motion of charged particles around magnetized black holes in conformally coupled scalar fields","authors":"Shokhzod Jumaniyozov , Javlon Rayimbaev , Yunus Turaev , Munisbek Akhmedov , Aybek Seytov , Jamshid Khasanov","doi":"10.1016/j.nuclphysb.2026.117318","DOIUrl":"10.1016/j.nuclphysb.2026.117318","url":null,"abstract":"<div><div>We investigate the dynamics of charged spinning test particles in the spacetime of a magnetized Bocharova-Bronnikov-Melnikov-Bekenstein black hole (BH), an extremal solution of the Einstein-Maxwell-conformally coupled scalar field equations. Using the Mathisson-Papapetrou-Dixon equations, we derive the equations of motion that incorporate spin-curvature coupling and electromagnetic interactions due to the particle’s charge and an external magnetic field. The effective potential formalism is employed to analyze stable circular orbits, the innermost stable circular orbit (ISCO), and the superluminal bound, ensuring timelike motion. The influence of the particle’s spin <em>s</em>, a magnetic coupling parameter <em>ω<sub>B</sub></em>, is examined numerically, revealing significant shifts in the ISCO radius, specific angular momentum, and energy due to spin and electromagnetic effects. We further study particle collisions near the event horizon, computing the critical angular momentum and center-of-mass energy, which exhibit enhancements akin to the Bañados-Silk-West effect, driven by gravitational, electromagnetic, and spin interactions. Our results highlight the intricate interplay of these effects in the BBMB spacetime, offering insights into high-energy astrophysical processes such as accretion disk dynamics and particle acceleration near magnetized BHs.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117318"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
We study the concept of a dark energy star, which is assumed to be composed of both dark and conventional matter in a modified teleparallel gravity. After employing a specific viable stellar model, we build the corresponding equations of motion that govern our further analysis. We then calculate the analytical form of the spherical geometric function, accompanied by an embedding class I choice, which states that the 4-dimensional geometry can be placed in a 5-dimensional planar space. With the help of a specific dark energy state equation, we model our system to investigate the role of dark energy on key stellar characteristics, such as equilibrium, star mass, and compactness, among other aspects, in the presence of torsion terms. This will lead us to investigate the stable epochs of the corresponding stellar structure through parameters such as pressure, mass function, density, and surface redshift, among others. We will then calculate the maximum allowable stellar matter quantity by utilizing the M-R diagram. It is inferred that, under certain parametric geometric zones, torsion-based correction supports a realistic and singularity-free star model. The system is seen to obey all energy conditions and stability criteria proposed by some theoretical backgrounds.
{"title":"Existence of class-I dark energy stellar models","authors":"Z. Yousaf , U.A. Khokhar , Javlon Rayimbaev , Otaboyev Sirajiddin , Aybek Seytov , M.Z. Bhatti","doi":"10.1016/j.nuclphysb.2026.117317","DOIUrl":"10.1016/j.nuclphysb.2026.117317","url":null,"abstract":"<div><div>We study the concept of a dark energy star, which is assumed to be composed of both dark and conventional matter in a modified teleparallel gravity. After employing a specific viable stellar model, we build the corresponding equations of motion that govern our further analysis. We then calculate the analytical form of the spherical geometric function, accompanied by an embedding class I choice, which states that the 4-dimensional geometry can be placed in a 5-dimensional planar space. With the help of a specific dark energy state equation, we model our system to investigate the role of dark energy on key stellar characteristics, such as equilibrium, star mass, and compactness, among other aspects, in the presence of torsion terms. This will lead us to investigate the stable epochs of the corresponding stellar structure through parameters such as pressure, mass function, density, and surface redshift, among others. We will then calculate the maximum allowable stellar matter quantity by utilizing the M-R diagram. It is inferred that, under certain parametric geometric zones, torsion-based correction supports a realistic and singularity-free star model. The system is seen to obey all energy conditions and stability criteria proposed by some theoretical backgrounds.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117317"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117326
Rita Rani , G.K. Goswami , J.K. Singh , Sushant G. Ghosh , Sunil D. Maharaj
We investigate a bouncing cosmological model within the Weyl-type f(Q) gravity framework, employing a power-law form of the non-metricity scalar Q. The model successfully resolves the initial singularity problem by demonstrating a nonsingular bounce, where the universe transitions from a contracting phase to an expanding phase () at the bouncing point t ≈ 0. Key features include the violation of the null energy condition (NEC) near the bounce and the crossing of the phantom divide line () by the equation of state (EoS) parameter, indicating quintom-like behavior. The model exhibits accelerated expansion post-bounce, suggesting an inflationary phase. Stability analysis via the adiabatic index reveals instability near the bouncing point, while energy conditions highlight the dominance of dark energy. Additionally, the study explores scalar fields, showing that quintessence-like kinetic energy becomes negative and phantom-like kinetic energy peaks positively near the bounce, aligning with dark energy dynamics. The Hubble parameter, deceleration parameter, and Hubble radius further validate the bouncing scenario, with the latter displaying symmetric behaviour around the bounce. These results underscore the viability of Weyl-type f(Q) gravity as a framework for nonsingular bouncing cosmologies, offering insights into early universe dynamics and dark energy behaviour.
{"title":"Scale-invariant bounce cosmology in Weyl f(Q) gravity with quintom signature","authors":"Rita Rani , G.K. Goswami , J.K. Singh , Sushant G. Ghosh , Sunil D. Maharaj","doi":"10.1016/j.nuclphysb.2026.117326","DOIUrl":"10.1016/j.nuclphysb.2026.117326","url":null,"abstract":"<div><div>We investigate a bouncing cosmological model within the Weyl-type <em>f</em>(<em>Q</em>) gravity framework, employing a power-law form of the non-metricity scalar <em>Q</em>. The model successfully resolves the initial singularity problem by demonstrating a nonsingular bounce, where the universe transitions from a contracting phase <span><math><mrow><mover><mi>a</mi><mo>˙</mo></mover><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo><</mo><mn>0</mn></mrow></math></span> to an expanding phase (<span><math><mrow><mover><mi>a</mi><mo>˙</mo></mover><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>></mo><mn>0</mn></mrow></math></span>) at the bouncing point <em>t</em> ≈ 0. Key features include the violation of the null energy condition (NEC) near the bounce and the crossing of the phantom divide line (<span><math><mrow><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></mrow></math></span>) by the equation of state (EoS) parameter, indicating quintom-like behavior. The model exhibits accelerated expansion post-bounce, suggesting an inflationary phase. Stability analysis via the adiabatic index reveals instability near the bouncing point, while energy conditions highlight the dominance of dark energy. Additionally, the study explores scalar fields, showing that quintessence-like kinetic energy becomes negative and phantom-like kinetic energy peaks positively near the bounce, aligning with dark energy dynamics. The Hubble parameter, deceleration parameter, and Hubble radius further validate the bouncing scenario, with the latter displaying symmetric behaviour around the bounce. These results underscore the viability of Weyl-type <em>f</em>(<em>Q</em>) gravity as a framework for nonsingular bouncing cosmologies, offering insights into early universe dynamics and dark energy behaviour.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117326"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117293
Muhammad Qasim , Asifa Ashraf , Muhammad Ramzan , Shabeela Malik , Shahid Iqbal , Fiaz Hussain
In this paper, we intend to explore Conformal Vector Fields (CVFs) of the Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model within the setup of f(Q, T) gravity, where Q denotes the non-metricity scalar and T is the trace of stress energy tensor. We start with a linear form of f(Q, T) gravity to solve equations of motion in the background of a type I LRS Bianchi cosmological model. We then follow a general form of the function f(Q, T) along with some additional constraints to explore exact space-times. With the help of such general form, we construct four types of non-trivial f(Q, T) gravity models. These models are in square root form, power law form, an exponential as well as a logarithmic form. Applying these f(Q, T) gravity models, we explore a variety of cosmological solutions admitting rotational symmetry. For these cosmological solutions, we find the CVFs. We observe that the constructed LRS Bianchi type-I solutions admit CVFs of dimension four, five, six, or fifteen. The physical entities like energy density and pressure associated with each Bianchi cosmological model are also being discussed.
{"title":"Perfect fluid Bianchi cosmological model admitting conformal motions in f(Q, T) gravity","authors":"Muhammad Qasim , Asifa Ashraf , Muhammad Ramzan , Shabeela Malik , Shahid Iqbal , Fiaz Hussain","doi":"10.1016/j.nuclphysb.2026.117293","DOIUrl":"10.1016/j.nuclphysb.2026.117293","url":null,"abstract":"<div><div>In this paper, we intend to explore Conformal Vector Fields (CVFs) of the Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model within the setup of <em>f</em>(<em>Q, T</em>) gravity, where <em>Q</em> denotes the non-metricity scalar and <em>T</em> is the trace of stress energy tensor. We start with a linear form of <em>f</em>(<em>Q, T</em>) gravity to solve equations of motion in the background of a type I LRS Bianchi cosmological model. We then follow a general form of the function <em>f</em>(<em>Q, T</em>) along with some additional constraints to explore exact space-times. With the help of such general form, we construct four types of non-trivial <em>f</em>(<em>Q, T</em>) gravity models. These models are in square root form, power law form, an exponential as well as a logarithmic form. Applying these <em>f</em>(<em>Q, T</em>) gravity models, we explore a variety of cosmological solutions admitting rotational symmetry. For these cosmological solutions, we find the CVFs. We observe that the constructed LRS Bianchi type-I solutions admit CVFs of dimension four, five, six, or fifteen. The physical entities like energy density and pressure associated with each Bianchi cosmological model are also being discussed.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117293"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117316
A. Khalid , A. Zahra , Muhammad Bilal Riaz , S.A. Mardan , Rubab Manzoor
In this manuscript, we explore two static and spherically symmetric, anisotropic, charged stars employing the formalism of modified f(R, T) gravity, where the gravitational Lagrangian is taken as . By introducing a core-envelope structure, we bring a new dimension to stellar modeling in modified gravity. Where the core follows a polytropic equation of state (EoS) and the envelope is modeled linearly. The internal spacetime continuously matched to the exterior Reissner–Nordstrm spacetime at the surface. We incorporate the effects of matter-geometry coupling by analyzing the physical quantities for three values of the coupling constant γ, offering new insights into how such coupling (associated with dark matter effects) influence stellar behavior. To validate the physical acceptability of the model, we examine key physical parameters and stability criteria, including density, pressure profiles, energy conditions, causality constraints, and the modified Tolman–Oppenheimer–Volkoff (TOV) equation. The stability of the model is further evaluated by the adiabatic index for astrophysical objects , . Our results demonstrate that the proposed model is physically free from singularity, and sensitive to the matter-geometry coupling. The significance of f(R, T) gravity in star’s modeling is highlighting with possible dark matter effects.
{"title":"Analysis of charged compact stars by core-envelope model in f(R, T) gravity","authors":"A. Khalid , A. Zahra , Muhammad Bilal Riaz , S.A. Mardan , Rubab Manzoor","doi":"10.1016/j.nuclphysb.2026.117316","DOIUrl":"10.1016/j.nuclphysb.2026.117316","url":null,"abstract":"<div><div>In this manuscript, we explore two static and spherically symmetric, anisotropic, charged stars employing the formalism of modified <em>f</em>(<em>R, T</em>) gravity, where the gravitational Lagrangian is taken as <span><math><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo><mo>=</mo><mi>R</mi><mo>+</mo><mn>2</mn><mi>γ</mi><mi>T</mi></mrow></math></span>. By introducing a core-envelope structure, we bring a new dimension to stellar modeling in modified gravity. Where the core follows a polytropic equation of state (EoS) and the envelope is modeled linearly. The internal spacetime continuously matched to the exterior Reissner–Nordstr<span><math><mover><mi>o</mi><mo>¨</mo></mover></math></span>m spacetime at the surface. We incorporate the effects of matter-geometry coupling by analyzing the physical quantities for three values of the coupling constant <em>γ</em>, offering new insights into how such coupling (associated with dark matter effects) influence stellar behavior. To validate the physical acceptability of the model, we examine key physical parameters and stability criteria, including density, pressure profiles, energy conditions, causality constraints, and the modified Tolman–Oppenheimer–Volkoff (TOV) equation. The stability of the model is further evaluated by the adiabatic index for astrophysical objects <span><math><mrow><mi>S</mi><mi>A</mi><mi>X</mi><mspace></mspace><mi>J</mi><mn>1808.4</mn><mo>−</mo><mn>3658</mn></mrow></math></span>, <span><math><mrow><mn>4</mn><mi>U</mi><mspace></mspace><mn>1608</mn><mo>−</mo><mn>52</mn></mrow></math></span>. Our results demonstrate that the proposed model is physically free from singularity, and sensitive to the matter-geometry coupling. The significance of <em>f</em>(<em>R, T</em>) gravity in star’s modeling is highlighting with possible dark matter effects.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117316"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01DOI: 10.1016/j.nuclphysb.2026.117327
Yuxuan Shi , A.A. Araújo Filho
We investigate how the newly obtained static black hole in bumblebee gravity affects the behavior of accreting matter and its observable signatures. The Lorentz–violating parameter that characterizes this geometry modifies photon trajectories and shifts the location of the critical curve that defines the shadow. Using ray tracing, we examine light deflection, the structure of direct emission, lensing rings, and photon rings, and we explore three thin–disk emission models–starting at the ISCO, at the photon sphere, and at the event horizon–together with static and infalling spherical accretions. Larger values of this parameter enlarge the shadow, move all optical features outward, and suppress the observed intensity through gravitational redshift, with additional dimming produced by Doppler effects for infalling matter.
{"title":"Accretion of matter of a new bumblebee black hole","authors":"Yuxuan Shi , A.A. Araújo Filho","doi":"10.1016/j.nuclphysb.2026.117327","DOIUrl":"10.1016/j.nuclphysb.2026.117327","url":null,"abstract":"<div><div>We investigate how the newly obtained static black hole in bumblebee gravity affects the behavior of accreting matter and its observable signatures. The Lorentz–violating parameter that characterizes this geometry modifies photon trajectories and shifts the location of the critical curve that defines the shadow. Using ray tracing, we examine light deflection, the structure of direct emission, lensing rings, and photon rings, and we explore three thin–disk emission models–starting at the ISCO, at the photon sphere, and at the event horizon–together with static and infalling spherical accretions. Larger values of this parameter enlarge the shadow, move all optical features outward, and suppress the observed intensity through gravitational redshift, with additional dimming produced by Doppler effects for infalling matter.</div></div>","PeriodicalId":54712,"journal":{"name":"Nuclear Physics B","volume":"1023 ","pages":"Article 117327"},"PeriodicalIF":2.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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