Fortschritte Der Physik-Progress of Physics最新文献

In the gauge theoretic approach of gravity, general relativity is described by gauging the symmetry of the tangent manifold in four dimensions. Usually the dimension of the tangent space is considered to be equal to the dimension of the curved manifold. However, the tangent group of a manifold of dimension d is not necessarily $��S�O_d�$. It has been suggested earlier that by gauging an enlarged symmetry of the tangent space in four dimensions one could unify gravity with internal interactions. Here, such a unified model is considered by gauging the $��S�O_{�(�1�,�17�)�}�$ as the extended Lorentz group overcoming in this way some difficulties of the previous attempts of similar unification and eventually obtained the $��S�O_{10}�$ GUT, supplemented by an $��S�U_2�\times �S�U_2�$ global symmetry.

Within the assumption of Left-Handed (LH) New Physics (NP), the relations between $��B�(�B�\to �K^{�(�*�)�}�{\tau }^{+}�{\tau }^{-}�)�$ and $��B�(�B�\to �K^{�(�*�)�}�\nu �\overline{\nu }�)�$ for several Beyond the Standard Model (BSM) scenarios are reviewed, commonly considered to explain the Lepton flavor Universality (LFU) violation observed in charged and neutral-current semileptonic B decays. The latest $�R_{D^{�(�*�)�}}$ world averages that include the recent LHCb measurement and assess the possibility of simultaneously explaining B-anomalies without spoiling current bounds on di-neutrino and di-tau modes are employed. This is particularly relevant in light of the upcoming results by Belle II on neutrinos and the continuing improvement in accuracy and sensitivity achieved in tau modes.

The cover picture shows a particular Mandelbrot fractal, which nicely describes a chaotic system in physics.

(Cover image © Astronira/Shutterstock)

The significant properties and phase transition of charged Anti-de Sitter (AdS) black holes have been extensively studied in a variety of modified theories of gravity in the presence of numerous matter fields. The goal of the current research is to investigate the AdS black hole's thermodynamics under the impact of $��f�\left(�Q�\right)�$ gravity. Additionally, this paper explores the black hole's local stability and phase structure under the relevant gravity. Besides, Ruppeiner geometry is used to look into the AdS black hole's microscopic structure. The Ricci curvature scalar R to explain the interactions between the AdS black hole's microscopic particles under the influence of $��f�\left(�Q�\right)�$ gravity have been numerically computed.

In this paper, cosmological aspects of metric-affine $��f�\left(�R�\right)�$ gravity with hyperfluid are studied. The equations of motion of the theory are obtained by varying the action with respect to the metric and the independent connection. Subsequently, considering a Friedmann-Lemaître-Robertson-Walker background, the modified Friedmann equations in the presence of a perfect cosmological hyperfluid is derived. Especially, a particular case in which $��f��\left(�R�\right)��=�R�+�\beta �R^2�$ is focused, considering purely shear hypermomentum and finding exact solutions in the weak coupling limit.

In order to unveil different features of gravitational waves due to massive objects like black hole etc., researchers primarily attempt to find the corresponding quasi normal modes from the relevant wave equations. In the present article, homotopy perturbation method (HPM) is employed to obtain the wave functions by solving wave equations for one-dimensional potential barriers. Under this scheme (i) for constant potential barrier a generalized solution which reduces to the known solution as done by Chandrasekhar and Detweiler [Proc. R. Soc. Lond. A 344 (1975) 441] is produced, (ii) the wave equation for the Price potential [Phys. Rev. D 5 (1972) 2419; Phys. Rev. D 5 (1972) 2439] by HPM is solved. The wave functions (graphically) as well as quasi-normal modes to those of the Press solution (1973) are compared. The present investigation is important in connection to further study related to the Zerilli potential and Regge-Wheeler potential in case of black hole.

While the configuration of a static spherically symmetric distribution of perfect fluid in an electric field has received extensive attention in the literature, only a few works have investigated the conformally flat case. The model exhibits a remarkable property being regular or singularity free is proposed. This is unexpected given that Coulombic repulsion opposes the collapse of a star to the center generally making the center unreachable. The conformally flat geometry thus enables the approach to the center of a charged star as shown in our model. Presently there is no known reported exact model that satisfies all the elementary requirements for physical acceptability. Some reported models that have claimed to be physically reliable have been shown to be deficient. The conditions for the existence of physically relevant models and show that exact solutions satisfying the conditions exist is investigated. Then a model satisfying all the requirements with isotropic particle pressure graphically for a carefully chosen parameter space is exhibited. The model admits a barotropic equation of state. The interior spacetime is successfully matched to the exterior Reissner-Nordstrom metric. The causality criterion as well as the adiabatic stability lower bound of Chandrasekar are shown to hold. The energy conditions are also valid within the stellar radius. Other interesting models are considered.