Fortschritte Der Physik-Progress of Physics最新文献

Many papers on modified gravity theories (MGTs), and metric-affine geometry have been published. New classes of black hole (BH), wormhole (WH), and cosmological solutions involving nonmetricity and torsion fields were constructed. Nevertheless, the fundamental problems of formulating nonmetric Einstein–Dirac–Maxwell (EDM), equations, and study of important nonmetric gravitational, electromagnetic and fermion effects, have not been solved in MGTs. The main goal of this work is to elaborate on a model of nonmetric EDM theory as a generalization of f(Q) gravity. The authors developed anholonomic frame and connection deformation method which allowed authors to decouple in general form and integrate nonmetric gravitational and matter fields equations. New classes of generated quasi-stationary solutions are defined by effective sources with Dirac and Maxwell fields, nonmetricity and torsion fields, and generating functions depending, in general, on all space-time coordinates. For respective nonholonomic parameterizations, such solutions describe nonmetric EDM deformations of BH and cosmological metrics. Variants of nonmetric BH, WH, and toroid solutions with locally anisotropic polarizations of the gravitational vacuum and masses of fermions, and effective electromagnetic sources, are constructed and analyzed. Such nonmetric deformed physical objects cannot be characterized in the framework of the Bekenstein–Hawking paradigm if certain effective horizon/holographic configurations are not involved. It is shown how to define and compute other types of nonmetric geometric thermodynamic variables using generalizations of the concept of G. Perelman W-entropy.

The physical scalar product between spin-networks has been shown to be a fundamental tool in the theory of topological quantum neural networks (TQNNs). These are a class of quantum neural networks supported on graphs and related to topological quantum field theory (TQFT), which have been previously introduced by the authors, recovering deep neural networks (DNNs) as their semiclassical limit. However, the effective evaluation of the scalar product remains an obstacle for the applicability of the theory. Inspired by decimation techniques for the computation of the partition function in statistical mechanics, an analytical technique is introduced for the exact evaluation of hexagonal spin-networks of arbitrary size, and describe the corresponding algorithm for the evaluation of the physical scalar product defined by Noui and Perez. The transition amplitudes on certain classes of spin-networks with both classical and quantum recoupling are investigated, obtaining a “continuous” spectrum of the transitions for the former and a discrete one for the latter. The theoretical and computational framework is expected to impact applications in string/tensor-networks for solid state physics, lattice gauge theories, and quantum gravity approaches.

This paper examines the thermodynamic properties and stability of deformed AdS-Schwarzschild black holes, focusing on the effects of deformation ($�\alpha$) and thermal correction parameters ($�{\beta }_1$, $�{\beta }_2$) on phase transitions and heat capacity. The results show that higher $�\alpha$ values raise the Hawking-Page critical temperature, enhancing thermal stability. Thermal corrections significantly affect smaller black holes but minimally impact larger ones, leaving second-order phase transitions unchanged. Heat capacity analysis identifies stability regions, with sign changes marking instability. These findings highlight the role of deformation and thermal corrections in black hole stability, offering insights for extending our understanding of black hole thermodynamics.

In this paper, the authors investigate the second-order normal quantum fluctuation on the worldsheet of a probe string in the Bañados–Teitelboim–Zanelli (BTZ) black hole. These fluctuations is treated as the projection of Hawking radiation on the worldsheet and indeed modify the action growth of the string. Then in the string field theory/boundary conformal field theory framework, via the boundary vertex operator, the authors study the correlation function of the Schrödinger functional of excited fields on the worldsheet and further extract the field's formula. This study could shed light on the potential connection between complexity growth and correlation function.

Action-dependent field theories are systems where the Lagrangian or Hamiltonian depends on new variables that encode the action. They model a larger class of field theories, including non-conservative behavior, while maintaining a well-defined notion of symmetries and a Noether theorem. This makes them especially suited for open systems. After a conceptual introduction, a quick presentation of a new mathematical framework is made for action-dependent field theory: multicontact geometry. The formalism is illustrated with a variety of action-dependent Lagrangians, some of which are regular and others singular, derived from well-known theories whose Lagrangians have been modified to incorporate action-dependent terms. Detailed computations are provided, including the constraint algorithm for the singular cases, in both the Lagrangian and Hamiltonian formalisms. These are the one-dimensional wave equation, the Klein–Gordon equation and the telegrapher equation, Maxwell's electromagnetism, Metric-affine gravity, the heat equation and Burgers' equation, the Bosonic string theory, and $��(�2�+�1�)�$-dimensional gravity and Chern–Simons equation.

Based on the Sen spacetime, the orbital energy and angular momentum are calculated, and the solution for the motion of a test particle derived to the second post-Newtonian order. The effect of the Sen black hole's charge $�q_m$ on the periastron advance and orbital period is obtained. In particular, it is found that $�q_m$ has an influence on perihelion precession at both the first and second post-Newtonian orders, whereas its effect on the orbital period is confined solely to the second post-Newtonian order. Finally, the precession of the star S2 is used to constrain our model and the value of $��q_m�/�M�$ is 0.51.