Fortschritte Der Physik-Progress of Physics最新文献

In this paper, a new definition of temperature is proposed for the FRW(Friedmann–Robertson–Walker) universe, i.e., the effective temperature $��T_{�e�f�f�}�:�=�d�E�/�d�S�$, where $�E$ is the energy and $�S$ is the entropy of the FRW universe. Based on this definition, the effective temperature is derived for the $�N$-dimensional FRW universe in Einstein gravity, Gauss–Bonnet gravity, and Lovelock gravity. For the 4-dimensional FRW universe, the effective temperature is found to be $��T_{�e�f�f�}�=�1�/��\left(�4�\pi �R_A�\right)��$, which is exactly the same form with the Hawking temperature of the Schwarzschild black hole. In higher-dimensional FRW universe, the form of the effective temperature depends on the choices of the gravitational theories or the corresponding coupling constants. The free energy of the FRW universe in the three theories of gravity is also obtained.

A model is presented that provides an explanation for the presence of (Dark Matter and) Dark Energy in the universe. A key idea is to express the volume form of the Lorentzian metric on space–time in terms of a positive function of a new scalar field multiplying a certain four-form given by the wedge product of the differential of the mimetic scalar field and a certain closed three-form. An ansatz for this three-form related to one commonly used to determine the winding number of a map from a three-dimensional hypersurface to a three-sphere is discussed. An action functional depending on the space–time metric, the new scalar field, the mimetic scalar and the three-form is proposed, and the field equations are derived. Special solutions of these equations for a Friedmann–Lemaître universe are presented.

A conformally extended Standard Model with a hidden scalar $�\varphi$ is investigated. It is shown that due to non-perturbative dynamics in the hidden sector, $�\varphi$ develops a vacuum expectation value (vev) in the form of a mass gap which triggers the electroweak symmetry breaking (EWSB) and dynamically generates the SM Higgs boson mass. To estimate the non-perturbatively generated mass scale, a hierarchy of Dyson–Schwinger equations is solved in form of partial differential equations using the exact solution known via a novel technique developed by Bender, Milton, and Savage. A Jacobi Elliptic function is employed as exact background solution and show that the mass gap that arises in the hidden sector can be transmuted to the EW sector, expressed in terms of Higgs-portal mixed quartic coupling $�\beta$ and self interaction quartic coupling $�{\lambda }_{\varphi }$ of $�\varphi$. The suitable parameter space where the observed SM Higgs boson can be successfully generated is identified. Finally, the idea of non-perturbative EW scale generation can serve as a new starting point for better realistic model building in the context of resolving the hierarchy problem in the Standard Model is discussed.

We define a metric $�G$ on the KBc-subalgebra modulo gauge and describe the worldsheet RG-flow as the gradient flow of the action of cubic open string field theory, where the flow lines are kink-solitons. In particular, for a constant tachyon the gradient flow equations are equivalent to the RG-equations. Additionally, a more general family of gradient flow lines is presented, which describes the RG-flow from the conformal manifold of the D-brane under tachyon condensation. We also derive the stability operator of our solution and show that the zero-modes reflect the invariance of the flow under such marginal perturbations. In fact, the beta function is colinear to our solution such that it describes geodesics from the conformal manifold to the tachyon vacuum with respect to $�G$.

This paper aims to propose a Cardy-like formula characterized by the mass, charge, and angular components of the black hole, along with their corresponding solitonic configuration, obtained through a double Wick rotation. The expression also incorporates the dynamical exponent and effective spatial dimensionality as key elements. To validate the proposal, a new concrete example is presented in which recovery of the semiclassical entropy requires the soliton to possess thermodynamic quantities beyond its mass. Additionally, more examples derived from static black hole solutions are presented, employing a Lorentz boost to calculate their thermodynamic parameters. Finally, a case of a rotating configuration is included, for which the Lorentz boost is not required.