We investigate the reconstruction of standard and generalized Rastall gravity inflationary models, using the scalar spectral index and the Rastall parameter expressed as functions of the number of <math altimg='si3.svg'><mrow><mi>e</mi><mo linebreak='goodbreak'>&#8722;</mo></mrow></math>folds <italic>N</italic>. Within a general formalism, we derive the effective potential in terms of the relevant cosmological parameters and the Rastall parameter for these gravity frameworks. As a specific example, we analyze the attractor <math altimg='si4.svg'><mrow><msub><mi>n</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>N</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>&#8722;</mo><mn>1</mn><mo>&#8733;</mo><msup><mi>N</mi><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></math>, first by considering constant values of the Rastall parameter to reconstruct the inflationary stage in standard Rastall gravity, and then by assuming a linear dependence on the number of <math altimg='si3.svg'><mrow><mi>e</mi><mo linebreak='goodbreak'>&#8722;</mo></mrow></math>folds <italic>N</italic> to reconstruct the inflationary model in generalized Rastall gravity. Thus, the reconstruction of the potential <italic>V</italic>( <italic>&#981;</italic>) is obtained for both standard and generalized Rastall gravity inflationary models. In both frameworks, we constrain key parameters of the reconstructed models during inflation using the latest observational data from Planck.

Chile

Ramón Herrera

Carlos Ríos

Reconstructing inflation in a generalized Rastall theory of gravity

The flavor-changing neutral current semileptonic decays of <italic>B</italic> mesons provide an excellent platform for indirectly probing New Physics (NP) beyond the Standard Model (SM). Recent measurements of lepton flavor universality (LFU) ratios such as <italic>R<inf>K</inf></italic>, <math altimg='si22.svg'><msub><mi>R</mi><msup><mi>K</mi><mo>*</mo></msup></msub></math>, and <italic>R<inf>&#981;</inf></italic> are consistent with SM predictions, thereby reducing earlier hints of LFU violation. Nevertheless, notable tensions persist in individual branching fractions&#8212;for instance <math altimg='si38.svg'><mrow><mi mathvariant='script'>B</mi><mo>(</mo><msup><mi>B</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>&#8722;</mo></msup><mo>)</mo></mrow></math> and <math altimg='si50.svg'><mrow><mi mathvariant='script'>B</mi><mo>(</mo><msup><mi>B</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup><mo>)</mo></mrow></math>, which deviate at the 4 <italic>&#963;</italic>&#8211;5 <italic>&#963;</italic> level in the low- <italic>q</italic> <sup>2</sup> region ([1.1,6] GeV <sup>2</sup>). Similarly, the angular observable <math altimg='si10.svg'><msubsup><mi>P</mi><mn>5</mn><mo>&#8242;</mo></msubsup></math> in <math altimg='si8.svg'><mrow><mi>B</mi><mo>&#8594;</mo><msup><mi>K</mi><mo>*</mo></msup><msup><mi>&#956;</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>&#8722;</mo></msup></mrow></math> shows a 3.3 <italic>&#963;</italic> deviation, while <math altimg='si128.svg'><mrow><mi mathvariant='script'>B</mi><mo>(</mo><msub><mi>B</mi><mi>s</mi></msub><mo>&#8594;</mo><mi>&#981;</mi><msup><mi>&#956;</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>&#8722;</mo></msup><mo>)</mo></mrow></math> departs from the SM by 3.6 <italic>&#963;</italic>. Although such discrepancies could in principle originate from underestimated hadronic effects, they may also indicate possible NP contributions. In this work, we perform a global fit to the latest <math altimg='si16.svg'><mrow><mi>b</mi><mo>&#8594;</mo><mi>s</mi><msup><mi>&#8467;</mi><mo>+</mo></msup><msup><mi>&#8467;</mi><mo>&#8722;</mo></msup></mrow></math> data within the framework of dimension-6 SMEFT operators. Our analysis systematically incorporates hadronic uncertainties from form factors, non-factorizable corrections, and input parameters, thereby providing a balanced assessment of the NP interpretation. We allow for NP contributions not only in <math altimg='si129.svg'><mrow><mi>b</mi><mo>&#8594;</mo><mi>s</mi><msup><mi>&#956;</mi><mo>+</mo></msup><msup><mi>&#956;</mi><mo>&#8722;</mo></msup></mrow></math> transitions but also in <math altimg='si130.svg'><mrow><mi>b</mi><mo>&#8594;</mo><mi>s</mi><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup></mrow></math> channels, thus testing both lepton flavor universal (LFU) and lepton flavor universality violating (LFUV) NP scenarios. The interplay between these possibilities yields distinctive signatures in branching fractions, angular observables, and &#916;-observables, offering a comprehensive view of the current flavor anomalies.

India

Md Isha Ali

Utpal Chattopadhyay

Dilip Kumar Ghosh

N. Rajeev

Constraints on lepton flavor universal and non-universal new physics in <math altimg='si127.svg'><mrow><mi>b</mi><mspace width='0.16em' /><mo>&#8594;</mo><mspace width='0.16em' /><mi>s</mi><mspace width='0.16em' /><msup><mi>&#8467;</mi><mo>+</mo></msup><msup><mi>&#8467;</mi><mo>&#8722;</mo></msup></mrow></math> decays: A global SMEFT survey

We study the effects of rotation on the confinement/deconfinement phase transition of strongly interacting matter, at low temperatures, in the soft wall AdS/QCD model at finite density. To achieve it, we apply the Hawking-Page approach to the exact Andreev’s solution of a charged rotating black hole in five-dimensional AdS space. We observe that there is a critical angular velocity ( <italic>&#969;</italic> <inf>0</inf>) of hadronic matter that depends on the baryon density, representing a strong constraint on the rotation in hadronic matter. We obtain the curve <italic>&#969;</italic> <inf>0</inf>( <italic>&#956;</italic>), which shows that the critical rotational velocity allowed for hadronic matter decreases as the chemical potential ( <italic>&#956;</italic>) increases. When <italic>&#956;</italic> approaches the most critical quark chemical potential, identified as the density of a phase transition at zero temperature for a non-rotating plasma, the rotational velocity allowed for the hadrons tends to zero. If <italic>&#969;</italic>&#8239;&#8805;&#8239; <italic>&#969;</italic> <inf>0</inf>, there is no phase transition and the QCD matter remains in the deconfined plasma phase. The QCD phase diagram is also obtained for the exact solution, and the critical temperatures are compared with the ones obtained from the Reissner-Nordstr&#246;m approximation. The results are interpreted as a consequence of contributions from regions relatively distant from the AdS boundary, which cause a non-negligible reduction in the deconfinement temperatures.

Brazil

Octavio C. Junqueira

Roldao da Rocha

Confinement/deconfinement at low temperatures and rotation in the exact soft wall model

We extend previous computations of Hermitian Yang–Mills connections for bundles on complete intersection Calabi–Yau manifolds to bundles on their free quotients. Bundles on quotient manifolds are often defined by equivariant bundles on corresponding covering spaces. Combining equivariant structure and the generalized Donaldson algorithm, we develop a systematic approach to compute connections of holomorphic poly-stable bundles on quotient manifolds. With it, we construct connections of an SU(3) bundle on a <math altimg='si1.svg'><msub><mi mathvariant='double-struck'>Z</mi><mn>5</mn></msub></math> quotient of the quintic and an SU(5) bundle on a <math altimg='si4.svg'><mrow><msub><mi mathvariant='double-struck'>Z</mi><mn>3</mn></msub><mo linebreak='goodbreak'>&#215;</mo><msub><mi mathvariant='double-struck'>Z</mi><mn>3</mn></msub></mrow></math> quotient of the bi-cubic. For both examples, the algorithm converges as expected and gives a good approximation of Hermitian Yang&#8211;Mills connections, which will be important for heterotic model building in Calabi&#8211;Yau compactifications.

China

Wei Cui

Numerical hermitian yang-Mills connection for bundles on quotient manifold

We show how the 2-Higgs Doublet Model (2HDM) Type-I can explain some excesses recently seen at the Large Hadron Collider (LHC) in <italic>&#947;&#947;</italic> and <math altimg='si29.svg'><mrow><msup><mi>&#964;</mi><mo>+</mo></msup><msup><mi>&#964;</mi><mo>&#8722;</mo></msup></mrow></math> final states in turn matching Large Electron Positron (LEP) data in <math altimg='si30.svg'><mrow><mi>b</mi><mover accent='true'><mi>b</mi><mo>&#175;</mo></mover></mrow></math> signatures, all anomalies residing around 95&#8239;GeV. The explanation to such anomalous data is found in the aforementioned scenario when in inverted mass hierarchy, in two configurations: i) when the lightest CP-even Higgs state is alone capable of reproducing the excesses; ii) when a combination of such a state and the CP-odd Higgs boson is able to do so. To test further this scenario, we present some Benchmark Points (BPs) of it amenable to phenomenological investigation.

Akshat Khanna

United Kingdom

Sweden

Stefano Moretti

Agnivo Sarkar

Explaining 95 GeV anomalies in the 2-Higgs doublet model type-I

Classical general relativity predicts a singularity at the center of a black hole, where known physical laws break down, suggesting the need for deeper principles of Nature. Among various theoretical possibilities, one promising proposal is a transition to a de Sitter phase at high curvatures near the black hole core. Originally proposed by Gliner and Sakharov, this transition ensures regular metric behavior and avoids singularities. In search of a regular black hole solution with finite curvature scalar, we propose a static, spherically symmetric metric featuring a de Sitter-like core. Notably, this solution admits a <italic>single event horizon</italic>, resembling the Schwarzschild geometry, and depends solely on the black hole mass, providing a connection with the Israel-Carter <italic>no-hair theorem</italic> for uncharged non-rotating black holes. To determine the underlying theory, we adopt a generalized <math altimg='si22.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>R</mi><mo>)</mo></mrow></math> model in place of the Einstein-Hilbert action. By numerically solving the modified field equations, we find that a Pad&#233; approximant in the Ricci scalar <math altimg='si23.svg'><mi mathvariant='script'>R</mi></math>, added to the Einstein-Hilbert term, yielding such regular solutions. We verify the physical viability of this model by confirming that the metric satisfies the null, weak, and dominant energy conditions throughout the spacetime. Additionally, the strong energy condition holds for <italic>r</italic>&#8239;&#8805;&#8239; <italic>r<inf>h</inf></italic>/2, consistent with Zaslavskii&#8217;s regularity criterion. The expansion scalar in the Raychaudhuri equation remains finite, and its derivative vanishes at the core ( <math altimg='si5.svg'><mrow><mi>r</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math>), preventing caustic formation. This ensures geodesic completeness and the absence of physical singularities.

Nihar Ranjan Ghosh

Malay K. Nandy

Geodesically complete regularized Schwarzschild black holes

Exploring exotic matter around black holes (BHs) under different conditions, using equations of state and astrophysical observational data from BHs, may deepen our understanding of the nature of dark matter and theories of gravity. In the present work, we first briefly introduce a BH solution surrounded by a dust field in <italic>f</italic>( <italic>R, T</italic>) gravity and study the properties of the horizon around the BH. We investigate scalar invariants of the spacetime geometry, such as the Ricci scalar, the square of the Ricci tensor, and the Kretchman scalar. We also study the circular motion of test particles. Additionally, we investigate the effects of the dust field on the innermost stable circular orbits (ISCOs) and the particle&#8217;s energy and angular momentum at the ISCO. Moreover, we investigate particle oscillations near ISCO around the BH and calculate the frequencies of Keplerian orbits and vertical oscillations. As an astrophysical application of the studies, we study quasiperiodic oscillations (QPOs) in various QPO models. Finally, we obtain constraints on the dust field and BH parameters using a Monte Carlo Markov Chain (MCMC) simulation across the multidimensional parameter space for the microquasars GRO J1655-40 &amp; GRS 1915-105, the Milky Way, and the M82 X-1 galaxy.

Uzbekistan

Abubakir Shermatov

Javlon Rayimbaev

Sardor Murodov

Pakistan

Bushra Majeed

Inomjon Ibragimov

Bahran Shermatov

Erkaboy Davletov

Ikram Davletov

Circular motion and QPOs near BHs surrounded by dust fields in <italic>f</italic>( <italic>R, T</italic>) gravity

The <italic>D</italic>(&#8239;&gt;&#8239;4) dimensional Einstein-Gauss-Bonnet(EGB) gravity is widely researched gravity that originates from the correction of quadratic curvature terms in Einstein-Hilbert action. Recently several methods have been suggested to obtain regularized EGB gravity in <italic>D</italic>&#8239;&#8594;&#8239;4 limit. The 4 <italic>D</italic> EGB gravity has drawn interests of researchers as it avoids Ostrogradsky&#8217;s instability and forecasts several cosmological phenomenon and black hole mechanics. In this paper we extensively study the effect of Gauss-Bonnet parameter and quintessence state parameter on black hole thermodynamics in EGB gravity by considering &#923; as thermodynamic pressure in AdS space. We examine critical behavior near critical, Gibbs free energy, local stability through heat capacity, Joule-Thomson expansion. We also obtained the efficiency of the newly proposed rectangular heat engine and found that it is always less than the Carnot efficiency, which is in agreement with the second law of black hole mechanics.

Debojyoti Mondal

Ujjal Debnath

Charged AdS black hole thermodynamics in Einstein-Gauss-Bonnet gravity under quintessence field: heat engine

This article examines the impact of <math altimg='si24.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>Q</mi><mo>)</mo></mrow></math> gravity parameters on analytical spherically symmetric solutions for compact objects. We employ two distinct metric ansatz to solve the equations of motion in <math altimg='si24.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>Q</mi><mo>)</mo></mrow></math> gravity. To assess the feasibility and reliability of our models, we analyze various physical properties, including pressure, mass function, energy density, stability, adiabatic index, energy conditions, and hydrostatic equilibrium through a graphical framework. Additionally, we demonstrate how the mass-radius relation and stability are influenced by the <math altimg='si24.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>Q</mi><mo>)</mo></mrow></math> theory parameter <italic>&#958;</italic> <inf>1</inf>. To validate our results, we estimate the radii of well-known compact objects, including PSR J0437-4715, 4U 1608-52, 2S 0921-630, SMC X-4, and Her X-1. Our analysis confirms that the obtained isotropic solutions are physically viable and exhibit significant clarity.

S. Ijaz

M.Z. Bhatti

Investigating compact stars in <math altimg='si24.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='script'>Q</mi><mo>)</mo></mrow></math> gravity: Analytical models and physical viability

We investigate the thermodynamic and dynamical properties of charged black holes influenced by nonlinear electromagnetic fields in the presence of a phantom global monopole. Focusing on the thermodynamic topology, we analyze the distribution and stability of topological charges derived from the free energy landscape, revealing a consistent total topological charge characteristic of the Reissner-Nordström black hole class. Extending this approach to photon sphere configurations, we demonstrate that their topological charges remain invariant under variations of the symmetry-breaking energy scale and coupling strengths, reflecting inherent geometric and thermodynamic stability. Additionally, we perform a comprehensive study of quasi-periodic oscillation (QPO) frequencies arising in the spacetime of such black holes, incorporating couplings to both phantom scalar and global monopole sectors. By systematically varying the monopole coupling parameter <italic>&#951;</italic>, the phantom coupling <italic>&#950;</italic>, and the magnetic charge <italic>Q</italic>, we elucidate their distinct influences on radial epicyclic, orbital, and periastron precession frequencies. Our results indicate that stronger monopole and phantom couplings suppress epicyclic oscillation amplitudes and shift characteristic frequencies outward, while increased magnetic charge stabilizes orbital motion closer to the black hole by lowering oscillation frequencies. These modifications suggest potential observational signatures in accretion phenomena and X-ray binaries, offering novel avenues to probe beyond-Einstein gravity in strong-field regimes. Future work will extend these analyses to rotating black holes, incorporate higher-order nonlinear electrodynamics effects, and explore implications for gravitational wave emissions.

Iran

Saeed Noori Gashti

Kazakhstan

Azerbaijan

Oman

Yassine Sekhmani

Canada

Mohammad Ali S Afshar

Mohammad Reza Alipour

Mohammadreza Khodajou Masouleh

Behnam Pourhassan

Jafar Sadeghi

Thermodynamic signatures in black hole geometry and harmonic oscillations with nonlinear electromagnetic fields and phantom global monopole