We show that gravitational leptogenesis with dynamical <italic>CPT</italic> breaking in an expanding universe can be reconciled with the exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity model, which introduces only one additional parameter <italic>&#946;</italic> compared to the standard &#923;CDM cosmology. This model incorporated axions as cold dark matter. For <italic>L</italic> violating interactions, we consider both a non-supersymmetric model with heavy right-handed neutrino decay and a supersymmetric model with sneutrino decay. For both cases, we have shown that the required baryonic asymmetry could be obtained. We have also shown the variation of decoupling temperature for lepton number violating interactions with the <italic>&#946;</italic> parameter in exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity. Lepton number-violating model parameters are constrained with the <italic>&#946;</italic> through the decoupling temperature. An upper bound on the <italic>&#946;</italic> parameter of the exponential <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> gravity is also obtained.

India

Suhail Khan

Ajay Bassi

Rathin Adhikari

Leptogenesis in exponential <italic>f</italic>( <italic>R</italic>) gravity model

We investigate the emergence of hidden conformal symmetry in the scalar wave equation for the accelerating Kerr–Newman black hole with arbitrary acceleration. By applying a near-horizon, low-frequency approximation, we reduce the quartic radial function to an effective quadratic form that reveals an underlying <math altimg='si1.svg'><mi>S</mi><mi>L</mi><msub><mrow><mo stretchy='false'>(</mo><mn>2</mn><mo>,</mo><mi mathvariant='double-struck'>R</mi><mo stretchy='false'>)</mo></mrow><mrow><mi>L</mi></mrow></msub><mo>&#215;</mo><mi>S</mi><mi>L</mi><msub><mrow><mo stretchy='false'>(</mo><mn>2</mn><mo>,</mo><mi mathvariant='double-struck'>R</mi><mo stretchy='false'>)</mo></mrow><mrow><mi>R</mi></mrow></msub></math> symmetry in the radial equation. This allows us to identify left- and right-moving temperatures and match the wave operator to the Casimir of a two-dimensional conformal field theory (CFT <inf>2</inf>). We compute the central charges from the near-horizon geometry of a near-extremal black hole and verify that the Cardy formula reproduces the Bekenstein&#8211;Hawking entropy. As further support for the Kerr/CFT correspondence in accelerating backgrounds, we analyze scalar field scattering and show that the absorption cross section agrees with the finite-temperature prediction from dual CFT <inf>2</inf> correlators. Our results provide both thermodynamic and dynamical evidence that the near-horizon region of the accelerating Kerr&#8211;Newman black hole admits a consistent holographic description by using the Kerr/CFT correspondence.

Indonesia

Haryanto M. Siahaan

Hidden conformal symmetry and holography for accelerating Kerr–Newman black holes

This study undertakes a reconsideration of the potential for a first-order electroweak phase transition, focusing on the next-to-minimal two Higgs doublet model (N2HDM). Our exploration spans diverse parameter spaces associated with the phase transition, with a particular emphasis on examining the generation of stochastic Gravitational Waves (GW) resulting from this transition. The obtained results are meticulously compared against data from prominent gravitational wave observatories, and the possibility of their detection in the future GW observations has been established. In passing by we analyze the strength of the phase transition through the production of entropy during the electroweak phase transition.

Japan

Arnab Chaudhuri

Kazunori Kohri

The N2HDM, Entropy Production and Stochastic Gravitational Waves

We investigate the dynamics of charged particles in the spacetime of a global monopole swallowed by a Reissner-Nordström (RN) black hole in the presence of an external, weak, asymptotically homogeneous magnetic field. We carefully analyze and deduce the conditions to have such a magnetic field around this black hole and show that this is indeed possible in the small but nontrivial charge and monopole term limit. We obtain the general equations of motion and analyze them for special cases of circular orbits, focusing on the innermost stable circular orbit (ISCO) of this configuration. The richness of the parameters and complicated forms of the resulting equations of motion necessitate a numerical approach. Hence, we have presented our results with numerous graphs, which help to understand the evolution of ISCO as a function of the external test magnetic field and the monopole term, depending on the parameters of the black hole, such as its electric charge, as well as the properties of the test particle, such as its specific charge, angular momentum, and energy. We have also analyzed the effective potential that these fields generate and deduced results for the aforementioned values of the external and internal parameters of the spacetime.

Hamza M. Haddad

M. Haluk Seçuk

Özgür Delice

Innermost stable circular orbits around a Reissner-Nordström-global monopole spacetime in a homogeneous magnetic field

Growth of entanglement entropy in time-dependent states formed due to a global quench in holographic conformal field theories which admit an Einstein-Gauss-Bonnet dual gravity description is studied. The global quench in the bulk is modelled by an AdS-Vaidya solution with an electric charge. It is observed that the Gauss-Bonnet correction parameter leads to faster thermalization, and lower saturation entropy. The rate of growth also depends crucially on the correction, and may exceed 1 in general spacetime dimensions. Nevertheless, the growth still follows the universal pattern expected for relativistic CFTs. Additionally, a time-dependent analogue of relative entropy introduced in <cross-ref refid='br0450' id='crf0040'>[1]</cross-ref> is generalized to include correction from the Gauss-Bonnet parameter. We demonstrate our findings through concrete examples, including instantaneous, linear, and periodically driven quenches. We also briefly mention the evolution of mutual information.

Sabyasachi Maulik

Soumen Pari

Entanglement entropy and its linear response following a global quench in holographic Gauss-Bonnet gravity

In this paper, we generally analyze the <math altimg='si1.svg'><mi>&#956;</mi><mo linebreak='goodbreak' linebreakstyle='after'>&#8722;</mo><mi>&#964;</mi></math> reflection symmetry modified by small mixings of charged leptons and how will future experiments verify deviations from the predictions of the symmetry. As an approximation, the left-handed diagonalization <math altimg='si2.svg'><msub><mrow><mi>U</mi></mrow><mrow><mi>e</mi></mrow></msub></math> of charged leptons is assumed to have a similar magnitude as the CKM matrix. In other words, the 1-3 mixing is neglected and the 1-2 and 2-3 mixing are to be approximately <math altimg='si3.svg'><mi>O</mi><mo stretchy='false'>(</mo><mn>0.1</mn><mo stretchy='false'>)</mo></math>. The Dirac CP phase <italic>&#948;</italic> of the MNS matrix is evaluated in such parameter regions. As a result, deviations from the predictions <math altimg='si4.svg'><mi mathvariant='normal'>sin</mi><mo>&#8289;</mo><msub><mrow><mi>&#952;</mi></mrow><mrow><mn>23</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi>&#960;</mi><mo stretchy='false'>/</mo><mn>4</mn></math> and <math altimg='si5.svg'><mi>&#948;</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mi>&#960;</mi><mo stretchy='false'>/</mo><mn>2</mn></math> depend on relative CP phases between <math altimg='si2.svg'><msub><mrow><mi>U</mi></mrow><mrow><mi>e</mi></mrow></msub></math> and diagonalization of neutrinos <math altimg='si6.svg'><msub><mrow><mi>U</mi></mrow><mrow><mi>&#957;</mi></mrow></msub></math>. While phases of the second and third generations cause only about <math altimg='si147.svg'><mo>&#177;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>&#8728;</mo></mrow></msup></math> deviations for the Dirac phase <italic>&#948;</italic>, the phase of the first generation can cause up to <math altimg='si183.svg'><mo>&#177;</mo><msup><mrow><mn>30</mn></mrow><mrow><mo>&#8728;</mo></mrow></msup></math>. This flavor dependence is distinguished to some extent by the next-generation experiments. On the other hand, if <italic>&#948;</italic> is not observed, such a scenario is excluded by about 5 years of observation.

Masaki J.S. Yang

Almost general analysis of <italic>&#956;</italic>&#8239;&#8722;&#8239; <italic>&#964;</italic> reflection symmetry perturbed by charged leptons and its testability by DUNE and T2HK

This article investigates the physical properties and stability of an isotropic compact star in <math altimg='si1.svg'><mi>F</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>Q</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo></math> gravity, where <math altimg='si2.svg'><mi mathvariant='script'>T</mi></math> denotes the trace of the energy-momentum tensor and <math altimg='si3.svg'><mi mathvariant='script'>Q</mi></math> represents the nonmetricity scalar. In the present study, the impact of <math altimg='si1.svg'><mi>F</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>Q</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo></math> gravity on the stability and structure of compact stars is investigated, considering a perfect fluid distribution and adopting the functional form <math altimg='si4.svg'><mi>F</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>Q</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>&#958;</mi></mrow><mrow><mn>1</mn></mrow></msub><mi mathvariant='script'>Q</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><msub><mrow><mi>&#958;</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant='script'>T</mi></math>. The field equations are solved using the two-step method proposed by Gupta and Jasim [Astrophys. Space Sci. 283 (2003) 337], along with the Buchdahl ansatz given by <math altimg='si110.svg'><msup><mrow><mi>e</mi></mrow><mrow><mi>&#966;</mi></mrow></msup><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi mathvariant='normal'>&#978;</mi><mo stretchy='false'>(</mo><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mi>&#1013;</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy='false'>)</mo></mrow><mrow><mi mathvariant='normal'>&#978;</mi><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mi>&#1013;</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math>. To investigate the physical properties of the LMC X-4 compact star, a static spherically symmetric metric is employed in the interior region, while a Reissner-Nordstrom exterior metric is adopted for the exterior region. In the interior region of the proposed stellar object, we analyze the behaviour of the spacetime metric functions ( <math altimg='si6.svg'><msup><mrow><mi>e</mi></mrow><mrow><mi>&#966;</mi></mrow></msup></math> and <math altimg='si7.svg'><msup><mrow><mi>e</mi></mrow><mrow><mi>&#977;</mi></mrow></msup></math>), energy density ( <italic>&#961;</italic>), pressure (P), charge (q), ratio of pressure to density (&#937;) and the energy conditions. The equilibrium state of the star is analysed using the Tolman-Oppenheimer-Volkoff (TOV) equation, expressed as <math altimg='si8.svg'><msub><mrow><mi>F</mi></mrow><mrow><mi>G</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>H</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><msub><mrow><mi>F</mi></mrow><mrow><mo stretchy='false'>(</mo><mi mathvariant='script'>Q</mi><mo>,</mo><mi mathvariant='script'>T</mi><mo stretchy='false'>)</mo></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><msub><mrow><mi>F</mi></mrow><mrow><mi mathvariant='double-struck'>Q</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>. To assess the stability of the configuration, we examine the adiabatic index (&#915;), the causality condition, regularity conditions, the well-behaved condition and the stability against convection criterion.

Sat Paul

Jitendra Kumar

Azerbaijan

Oman

S.K. Maurya

Saudi Arabia

Akram Ali

Most general exact solution for charged compact star model in extended symmetric teleparallel gravity using two step-method

Symmetry packaging is the phenomenon whereby, upon particle creation, all the internal quantum numbers (IQNs) become locked into a single irreducible representation (irrep) block of the gauge group, as required by locality and gauge invariance. The resulting packaged quantum states exhibit characteristic symmetry constraints and entanglement patterns. We develop a group-theoretic framework to describe the symmetry packaging for a variety of concrete symmetries and to classify the corresponding packaged states:

Canada

Rongchao Ma

Symmetry packaging II: A group-theoretic framework for packaging under finite, compact, higher-form, and hybrid symmetries

We extend the computation of the <math altimg='si1.svg'><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub></math> charge of the 2-point function of the Energy-Momentum Tensor to 4-loops. We show that <math altimg='si1.svg'><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub></math> decomposes into two sectors, the conformal sector, which encodes the value of the central charge at fixed points and an RG-sector that contains logarithmic and constant corrections proportional to the <italic>&#946;</italic>-function. This latter constitutes the main new result of this work and is inaccessible via CFT methods alone. Furthermore, we demonstrate that <math altimg='si1.svg'><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub></math> satisfies an eigenvalue-like equation analogous to that of the spin-0 charge, as discussed in part I, though with a different in general eigenvalue. Finally we present three possible applications.

Greece

Nikos Irges

Leonidas Karageorgos

Energy momentum tensor correlators in <italic>&#981;</italic> <sup>4</sup> theory II: The spin-two sector

Modified theories of gravity have offered compelling alternatives for addressing the stability and structural features of self-gravitating systems. In this work, we explore the dynamics of anisotropic compact objects within the framework of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>T</mi><mo>,</mo><mi mathvariant='script'>Q</mi><mo stretchy='false'>)</mo></math> gravity using an extended gravitational decoupling approach. Starting with a spherically symmetric anisotropic seed solution, we incorporate an additional gravitational source and formulate the corresponding field and conservation equations under strong matter-geometry coupling. The analytical structure is developed by imposing matching and Kuchowicz conditions to determine the unknown metric functions. Furthermore, we introduce a complexity-free condition along with an isotropized constraint to analyze the influence of coupling effects on the physical viability and stability of the system. Our results indicate that the matter-curvature interaction significantly enhances the stable configurations and reduces the overall complexity of the system. The impact of the decoupling parameter is also studied to illustrate the sensitivity of physical parameters, supported through graphical analysis. These findings provide deeper insight into the role of extended gravity and anisotropic effects in the formation and evolution of compact stellar objects.

Pakistan

U. Farwa

A. Abbas

M. Yousaf

Field-theoretic construction of complexity-free anisotropic stars via extended decoupling