This work employs the minimal geometric deformation decoupling scheme to derive interior stellar solutions in the background of an electrically charged BTZ ansatz as a seed metric in three dimensions. In this respect, we impose two different equations of state to determine the deformation function and the new material contributions emerging from the additional field source. Furthermore, we describe the finiteness of all thermodynamic quantities of the presented stellar solutions, including the effective thermodynamical quantities, for varying values of the deformation parameter and total electric charge. We explore the new interior astrophysical solutions in three-dimensional gravity by analyzing the charged BTZ metric, admitting circular symmetry through the principles of geometric deformation. This study examines the impact of radial-metric deformation on the charged BTZ geometry and underscores the importance of stellar decoupling within the context of electrically charged dense distributions. It is shown that new physically acceptable solutions by incorporating any known three-dimensional spacetime as the isotropic basis are possible, which in turn enable one to analyze the quantum effects due to low degrees of freedom at lower dimensions.

Pakistan

Z. Yousaf

Japan

Kazuharu Bamba

Saudi Arabia

Mansoor Alshehri

S. Khan

Azerbaijan

M.Z. Bhatti

Physical features of geometrically deformed anisotropic charged three-dimensional BTZ black holes

In this paper, we have tested the non-unitary mixing hypothesis with the latest data from NO <italic>&#957;</italic>A and T2K experiments. We have also analysed their combined data. We have provided the best-fit values of the standard and non standard parameters after the analysis. 90% limits on the non-unitary mixing parameters have also been provided. The constraints on unitary violation is stronger, compared to the constraints obtained from previous data from NO <italic>&#957;</italic>A and T2K. The tension between NO <italic>&#957;</italic>A and T2K at the 1&#8201; <italic>&#963;</italic> for normal mass hierarchy can be reduced for non-unitary mixing due to <italic>&#945;</italic> <inf>10</inf>, albeit for a value of | <italic>&#945;</italic> <inf>10</inf>| larger than the present global 90% limit. Additionally a study of the future sensitivity of NO <italic>&#957;</italic>A, T2K and DUNE has been provided.

Canada

Xin Yue Yu

Zishen Guan

Ushak Rahaman

Nikolina Ilic

Update on non-unitary mixing in the recent NO <italic>&#957;</italic>A and T2K data

We investigate exact charged and uncharged black hole solutions in a (2+1)-dimensional spacetime within the framework of quadratic form of <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> symmetric teleparallel gravity, where <math altimg='si15.svg'><mi mathvariant='double-struck'>Q</mi></math> is the non-metricity scalar. By adopting spherical symmetry and considering both vanishing and non-vanishing electromagnetic fields, we derive new classes of black hole solutions and analyze their geometric and physical properties. The study demonstrates that the inclusion of quadratic corrections in the gravitational Lagrangian significantly modifies the structure of solutions, producing deviations from the standard BTZ geometry. Invariants such as curvature and non-metricity scalars are calculated to classify the singularity structure and spacetime behavior. Thermodynamic quantities, including Hawking temperature, entropy, and heat capacity, are computed, showing consistency with the first law of black hole thermodynamics. Furthermore, we examine the geodesic motion of test particles and derive the effective potential to explore the stability of photon orbits. A notable outcome is the identification of weaker black hole singularities in comparison to General Relativity, attributed to the non-metricity corrections. The possibility of multi-horizon configurations is also explored. This study provides a comprehensive analysis of the gravitational, thermodynamic, and dynamical features of lower-dimensional black holes in <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> gravity and highlights their distinct characteristics with respect to General Relativity.

Egypt

Gamal G.L. Nashed

Italy

Salvatore Capozziello

Stable black holes in lower dimensional <math altimg='si2.svg'><mrow><mi>f</mi><mo>(</mo><mi mathvariant='double-struck'>Q</mi><mo>)</mo></mrow></math> non-metric gravity

We generate a radiating star in Einstein-Gauss-Bonnet (EGB) gravity for spacetime dimension <math altimg='si10.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>5</mn></mrow></math> and a shear-free geometry. The temporal boundary condition contains curvature corrections from the Lovelock tensor and reduces to the general relativity limit. A detailed analysis of the model indicates that the temporal evolution of the star is qualitatively different from general relativity. Firstly, the phase plane analysis shows that the phase trajectories are less constrained due to the Gauss-Bonnet parameter. Secondly, separable metrics in EGB gravity imply that shear-free collapse generates anisotropic pressures; the corresponding isotropic configurations in general relativity cannot arise because of the EGB curvature corrections. Remarkably it is possible to find radiating models in pure EGB gravity which involve Lambert functions. The symmetries associated with the EGB boundary condition have a structure different from general relativity. The self-similar nature of general relativity is lost in pure EGB gravity. Consequently, radiating bodies in EGB gravity possess distinct geometrical and physical features.

South Africa

Sunil D. Maharaj

Byron P. Brassel

Sumeekha Singh

Keshlan S. Govinder

A radiating star in Einstein-Gauss-Bonnet gravity

The Khovanov-Rozansky (KR) link polynomial is a certain <italic>t</italic>-deformation of Wilson loops in 3-dimensional <italic>SU</italic>( <italic>N</italic>) Chern-Simons topological field theory, believed to be an observable in the refined Chern-Simons theory, probably described in terms of 4d or 5d QFT and related by a certain procedure to the triply-graded link &lt;&lt;superpolynomial&gt;&gt;. This link invariant was originally introduced by M. Khovanov and L. Rozansky through a sophisticated matrix factorization technique based on the bicomplex structure, which depends on entire link diagrams and rapidly increases in complexity with the growth of a link. However, for particular link diagrams a local reduction is possible, allowing to eliminate vertices in a regular way, and thus, simplifying the KR polynomial and making it as simple as the Khovanov polynomial in the <math altimg='si1.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math> case. In particular, for a distinguished family of bipartite links, matrix factorization defined on MOY diagrams reduces just to planar cycles &#8211; very similar to the original Kauffman-Khovanov construction at <math altimg='si1.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math> for the Jones polynomial and its <italic>t</italic>-deformation. In the bipartite case, this can be done for any <italic>N</italic>. We make a further step of simplification and reduce from cohomology factor-rings in even variables crucially depending on a MOY diagram to vector spaces spanned by odd variables, so that the initial bicomplex of matrix factorizations becomes a monocomplex of just tensor products of <italic>N</italic>-dimensional vector spaces. We also find the explicit form of three universal morphisms which were guessed in a recent paper on this subject. Universality means independence of the other edges of the diagram, and we explain why this works in this particular case.

Russia

E. Lanina

R. Stepanov

Khovanov-Rozansky matrix factorization reduction for bipartite links

We provide a simple yet effective semi-analytical approach to confront Mukhanov Parametrization of inflationary equation-of-state, <math altimg='si6.svg'><mrow><mn>1</mn><mo linebreak='goodbreak'>+</mo><mi>&#969;</mi><mo linebreak='goodbreak'>=</mo><mfrac><mi>&#946;</mi><msup><mrow><mo>(</mo><mi>N</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow><mi>&#945;</mi></msup></mfrac></mrow></math>, with the latest ACT-DR6 data employing Hamilton-Jacobi formulation. We find that the equation-of-state formalism renders excellent fit to the most recent observational data. In the process we are also able to put stringent constraint on the two model parameters. In order to constrain the model parameters <italic>&#945;</italic> and <italic>&#946;</italic> we have also made use of the recent finding <italic>r</italic>&#8239;&lt;&#8239;0.032. We have further utilized results from the joint analysis of ACT-DR6, Planck-2018 and DESI-Y1 data to find the observationally viable region for <italic>&#945;</italic> and <italic>&#946;</italic>. We have also employed the predictions on primordial gravitational waves from forthcoming CMB missions in the likes of CMB-S4 and LiteBIRD along with results from the combined analysis of ACT-DR6, Planck-2018 and DESI-Y1 data to further restrict the model parameters. We find that detection of gravitational waves would narrow the viable parameter space for Mukhanov parametrization. But in the absence of detection of primordial tensor mode signal by those CMB missions parameter space is reduced significantly for <italic>&#946;</italic>, while the range of <italic>&#945;</italic> remaining almost constant. In addition we observe that, <italic>&#945;</italic> is primarily dependent on the observationally viable range for scalar spectral index while other model parameter <italic>&#946;</italic> is resting heavily on the restriction upon the tensor-to-scalar ratio. Moreover, we find that equation-of-state formalism has a wide range of parameter values consistent with recent observational data along with futuristic CMB missions in the likes of CMB-S4 and LiteBIRD. Interestingly, our analysis shows that the joint ACT-DR6, Planck-2018, DESI-Y1, and BICEP/Keck-2018 constraints restore the viability of the monomial class of inflationary models represented by <italic>&#945;</italic>&#8239;&#8771;&#8239;1, while ruling out very small-field models, <italic>&#945;</italic>&#8239;&#8805;&#8239;3. We have also found classical Starobinsy model just lie within 95% confidence level boundary of the joint analysis of ACT-DR6, Planck-2018, DESI-Y1 and BICEP/Keck-2018 data.

India

Barun Kumar Pal

Confronting mukhanov parametrization of inflationary equation-of-State with ACT-DR6

We applied the newly introduced <italic>f</italic>( <italic>T</italic>) gravity framework to study cosmological models involving viscous fluids with the FLRW Universe. We assume a bulk viscosity coefficient of the form <math altimg='si19.svg'><mrow><mi>&#950;</mi><mo linebreak='goodbreak'>=</mo><msub><mi>&#950;</mi><mn>0</mn></msub><msup><mi>H</mi><mn>2</mn></msup></mrow></math> with <math altimg='si20.svg'><mrow><mi>f</mi><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow><mo linebreak='goodbreak'>=</mo><mi>&#945;</mi><msup><mi>T</mi><mn>2</mn></msup></mrow></math>, <bold>where</bold> <italic>&#950;</italic> <inf>0</inf> and <italic>&#945;</italic> <bold>are model parameters.</bold> We use several observation datasets, such as recent Baryon Acoustic Oscillations (BAO) data, an updated Hubble dataset with 31 point, and 1701 Pantheon+ data point. Our model shows excellent agreement with observational data, and statistical analysis provides the optimal values for its parameters. We also investigate how key cosmological parameters evolve, specifically the deceleration parameter <italic>q</italic>, density parameter, and equation of state parameter <italic>&#969;</italic> <inf>eff</inf>. Our study suggests that the Universe transitions from a decelerated phase to an accelerated expansion phase. The accelerated expansion is consistent with the EoS parameter, which falls within the quintessence regime <math altimg='si21.svg'><mrow><mo>&#8722;</mo><mn>1</mn><mo linebreak='goodbreak'>&lt;</mo><msub><mi>&#969;</mi><mtext>eff</mtext></msub><mo linebreak='goodbreak'>&lt;</mo><mo>&#8722;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac></mrow></math>, supporting the current rapid growth. According to our findings, bulk viscosity may be included in the <italic>f</italic>( <italic>T</italic>) gravity framework to accurately simulate dark energy and is in line with the conventional cosmological scenario

Bharat Singh

S. Surendra Singh

Observational analysis of bulk viscous cosmological model in <italic>f</italic>( <italic>T</italic>) gravity

With the recent revival of interest in the FLPR model, novel features have been reported in the literature. A connection between those new feautures and QCD, involving the Gribov problem, is explored. We investigate the FLPR model in a recently proposed framework of BRST-related symmetries and perform its full functional quantization as a gauge invariant system taking into account the Gribov ambiguities and produce a consistent generating functional which can be used as a starting point for the Gribov-Zwanziger-Sorella program. We obtain a family of BRST-related transformations generated by the discrete group of symmetries of the action. We show that gauges possessing Gribov ambiguities lead to a violation of the initial discrete group of symmetries of the gauge-fixed action. The obtained results shed light into similar issues in QCD by the corresponding association of variables and fields between the two systems.

Bhabani Prasad Mandal

Sumit Kumar Rai

Brazil

Ronaldo Thibes

On BRST-related symmetries in the FLPR model with Gribov ambiguities

It is well-known that within the standard three flavor neutrino oscillation formalism, the Majorana phases appearing in the neutrino mixing matrix cannot have any effect on neutrino oscillation probabilities thereby evading testability at neutrino oscillation experiments. We consider an effective non-Hermitian Hamiltonian describing three flavor neutrino oscillations with the possibility of neutrino decay and demonstrate that the two Majorana phases can entangle with the off-diagonal decay terms and appear at the level of oscillation probabilities. Using the Cayley-Hamilton theorem, we derive approximate analytical expressions for three flavor neutrino oscillation probabilities in the presence of neutrino decay, taking into account matter effects. In the context of a long baseline neutrino experiment, we then analyse the impact of Majorana phases on the oscillation probabilities for different channels as well as on observables related to CP violation effects in neutrino oscillations. Finally, we discuss the effect of Majorana phases on the parameter degeneracies in the neutrino oscillation framework.

Sabila Parveen

United States

Soumya Bonthu

Spain

Newton Nath

Ujjal Kumar Dey

Poonam Mehta

Majorana CP violation insights from decaying neutrinos

In this paper, we investigate Lyapunov exponents associated with chaotic motions of both massless and massive particles in the vicinity of a Kerr-Newman AdS black hole. Our exploration focuses on their correlations with the black hole phase transition and the chaos bound. The results demonstrate that these exponents serve as effective probes of the phase transition, with the chaotic Lyapunov exponent of the massless particle offering a more precise characterization. Further calculations indicate that critical exponents linked to these Lyapunov exponents are uniformly 1/2. Notably, the violation of the chaos bound occurs irrespective of whether a phase transition is taking place. Through comparative analysis, we identify a critical radius, and the violation consistently arises when the black hole’s radius is less than this critical radius. Moreover, this violation is observed in the spacetime of the stable small black hole during the phase transition.

China

Chuang Yang

Malaysia

Chuanhong Gao

Deyou Chen

Xiaoxiong Zeng

Lyapunov exponents, phase transition and chaos bound in Kerr-Newman AdS spacetime