Fortschritte Der Physik-Progress of Physics最新文献

In this paper, the cosmic evolution in the context of five-dimensional Einstein Chern-Simons gravity theory by using flat homogeneous and isotropic universe model is studied. The interaction is taken into account between dark sector of the evolving universe along with holographic dark energy model with Hubble horizon. Our study with well-known models EChS -β₅ and EChS -$�\stackrel{\sim }{{\beta }_5}$ for Einstein Chern-Simons gravity theory in five dimensions are carried. Some cosmological parameters through graphical representations such as coincidence parameter u, equation of state parameter $�{\omega }_{\Lambda }$, deceleration parameter q and squared speed of sound parameter $�v_s^2$ is analyzed. It is found that these cosmological parameters show consistent behavior with current cosmic scenario. Also, the behavior of generalized second law of thermodynamics in the underlying gravity theory with Bekenstein-Hawking entropy and its validity for some fixed values of constants appearing in each model are explored.

The topological structures that arise from two-dimensional (2D) models are relevant physically and the first step toward understanding more complex systems. In this work, one studies the kink-like solutions of the matter field that emerge in a 2D dilaton gravity scenario. Considering this scenario, the linear stability of the matter field and the translational mode is examined. Due to the specific profile of the solutions found, a differential configurational complexity (DCC) analysis of the system is necessary to confirm the nature of the structures. Furthermore, the interforce and scattering process is studied, considering a pair of kink-antikink-like solutions in a fixed time ($��t�=�0�$).

Euclidean Wilson loops for BMN Plane Wave Matrix Models is computed. The stringy counterpart of these Wilson loops corresponds to various semi-classical open string embedding that probe a class of half BPS geometries in Type IIA supergravity. These geometries fall under the general category of Lin-Lunin and Maldacena (LLM). As a special class of solutions within the LLM category, Wilson operators corresponding to the non-Abelian T dual (NATD) of $��A�d�S_5�\times �S^5�$ is constructed. The analysis shows close agreement between matrix model and string theory calculations.

For the first time the direct construction of string models on quantum annealers has been explored and has been investigated their efficiency and effectiveness in the model discovery process. Through a thorough comparison with traditional methods such as simulated annealing, random scans, and genetic algorithms, it is highlighted the potential advantages offered by quantum annealers, which in this study promised to be roughly 50 times faster than random scans and genetic algorithm and approximately four times faster than simulated annealing.

Taking the Noether gauge symmetry approach into account, spherically symmetric static black hole solutions of the non-minimal gauge-gravity Lagrangian of the $��R^{\beta }�F^2�$ model is found. At first, a system of differential equations for the general non-minimal couplings of $��Y��\left(�R�\right)��F^2�$ type is considered, and then, it is regarded as a particular $��R^{\beta }�F^2�$ non-minimal model to find the exact black hole solution and analyze its symmetries. As the next step, the thermodynamical quantities of the black hole and its interesting behavior is calculated. Besides, thermal stability and examining the possibility of the van der Waals-like phase transition is addressed.

Energy conditions and quasinormal modes (QNMs) for scalar perturbations of regular charged black holes within the framework of General Relativity coupled to non-linear electrodynamics (NLE) are discussed. The frequencies are computed numerically adopting the WKB method, while in the eikonal limit an analytic expression for the spectra is obtained. The impact of the electric charge, the angular degree, and the overtone number on the spectra is investigated in detail. All frequencies are characterized by a negative imaginary part, and that each type of energy conditions imply a different quasinormal spectrum are found.

In this paper, a well-motivated parameterization of the Hubble parameter (H) is revisited that renders two models of dark energy showing some intriguing features of the late-time accelerating Universe. A general quintessence field is considered as a source of dark energy. Tighter constraints using recently updated cosmic observational datasets for the considered models have been obtained. The two models described here show a nice fit to the considered uncorrelated Hubble datasets, Standard candles, Gamma Ray Bursts, Quasars, and uncorrelated Baryonic Acoustic Oscillations datasets. Using the constrained values of the model parameters, some features of the late-time accelerating models and obtained the present value of the deceleration parameter (q₀), the present value of the Hubble parameter (H₀) and the transition redshift ($�z_t$) from deceleration to acceleration have been discussed. The current value of the deceleration parameter for both models is consistent with the Planck 2018 results. The evolution of the geometrical and physical parameters is discussed through graphical representations for both models with some diagnostic analysis. The statistical analysis performed here shows greater results and overall, the outcomes of this investigation are superior to those previously found.

This paper presents a dual gravity model for a (2+1)-dimensional system with a limit on finite charge density and temperature, which will be used to study the properties of the holographic phase transition to paramagnetism-ferromagnetism in the presence of Horndeski gravity terms. In our model, the non-zero charge density is supported by a magnetic field. As a result, the radius $��\rho �/�B�$ indicates a localized condensate, as the Horndeski gravity parameter is increased, that is represented by γ. Furthermore, such condensate shows quantum Hall-type behavior. This radius is also inversely related to the total action coefficients of our model. It is observed that increasing the Horndeski parameter decreases the critical temperature of the holographic model and leads to the harder formation of the magnetic moment at the bottom of the black hole. However, when removing the magnetic field, the ferromagnetic material presents a disorder of its magnetic moments, which is observed through the entropy of the system. The authors also found that at low temperatures, spontaneous magnetization and ferromagnetic phase transition.

The investigation of thin accretion disc surrounding the Einstein- Euler- Heisenberg- Anti- de Sitter black hole is demonstrated. Additionally, the black hole event horizons and compute their effective potential and equations of motion is analyzed. The specific energy, specific angular momentum, and specific angular velocity of the particles that move in circular orbits above the thin accretion disk are obtained. Also, the effects of parameters of the Einstein- Euler- Heisenberg- Anti De sitter black hole on specific angular velocity, specific heat energy, and specific angular momentum, have been discussed in detail. The positions of the innermost stable circular orbits and illustrate the effective potential are displayed. Furthermore, the circular orbits of black hole are obtained numerically and locates the position of the innermost stable circular orbit and event horizon. Also, the Gamma ray burst emitted from the Einstein Euler Heisenberg Anti de sitter black hole is studied.

In recent years, $��f�\left(�Q�\right)�$ gravity has enjoyed considerable attention in the literature and important results have been obtained. However, the question of how many physical degrees of freedom the theory propagates—and how this number may depend on the form of the function f—has not been answered satisfactorily. In this article it is shown that a Hamiltonian analysis based on the Dirac-Bergmann algorithm—one of the standard methods to address this type of question—fails. The source of the failure is isolated and it is shown that other commonly considered teleparallel theories of gravity are affected by the same problem. Furthermore, it is pointed out that the number of degrees of freedom obtained in Phys. Rev. D 106 no. 4, (2022) by K. Hu, T. Katsuragawa, and T. Qui (namely eight), based on the Dirac-Bergmann algorithm, is wrong. Using a different approach, it is shown that the upper bound on the degrees of freedom is seven. Finally, a more promising strategy for settling this important question is proposed.