Nuclear Physics B最新文献

We summarize our theory on existence, uniqueness and regularity of solutions for linear equations in infinitely many derivatives of the form$f\left({\partial }_t\right)\varphi =J\left(t\right),t\ge 0,$ where f is an analytic function such as the (analytic continuation of the) Riemann zeta function. We explain how to analyse initial value problems for these equations, and we prove rigorously that the function$\varphi \left(t\right)=\sum _{n\ge 1}\frac{\mu \left(n\right)}{n^h}J(t-\ln (n\left)\right),$ in which μ is the Möbius function and J satisfies some technical conditions to be specified in Section 4, is the solution to the zeta nonlocal equation$\zeta ({\partial }_t+h)\varphi =J\left(t\right),t\ge 0,$ in which ζ is the Riemann zeta function and $h>1$. We also present explicit examples of solutions to initial value problems for this equation. Our constructions can be interpreted as highlighting the importance of the cosmological daemon functions considered by Aref'eva and Volovich (2011) [1]. Our main technical tool is the Laplace transform as a unitary operator between the Lebesgue space $L^2$ and the Hardy space $H^2$.

In the present work, we construct models of static wormholes in 4-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity with an (an)isotropic energy momentum tensor (EMT) and a Maxwell field as supporting matters for the wormhole geometry assuming a constant redshift function. We obtain exact spherically symmetric wormhole solutions in 4D EGB gravity for isotropic and anisotropic matter sources under the effect of electric charge. The solutions are more generalized in the sense of incorporating the charge contributions. Furthermore, we examine the null, weak and strong energy conditions at the wormhole throat of radius $r=r_0$. We demonstrate that at the wormhole throat, the classical energy conditions are violated by arbitrary small amount. Additionally, we analyze the wormhole geometry incorporating semiclassical corrections through embedding diagrams. We discover that the wormhole solutions are in equilibrium as the anisotropic and hydrostatic forces cancel each other.

I summarize the apparent relevance of anthropic selection in understanding unnatural features of the Standard Model, and the consequent implications for theory. This topic, pioneered by Weinberg, could make him the last giant of physics.

In this study, we present a approach to mimetic gravity incorporating a non-zero nonmetricity tensor with vanishing torsion and curvature, establishing a generalized mimetic-$f\left(Q\right)$ gravity framework. Using the Lagrange multiplier method, we have obtained and discussed characteristics of the theory's field equations. In order to study cosmic evolution given by the hybrid scale factor, we implemented the reconstruction method in two different ways. In the first case, we have obtained corresponding Lagrange multiplier η and potential U for the specific $f\left(Q\right)=f\left(Q\right)=Q-6\lambda M^2{\left(\frac{Q}{6M^2}\right)}^{\alpha }$ function, while in the second scenario we have recovered $f\left(Q\right)$ functional and mimetic potential for the given Lagrange multiplier ${\eta }_0+\gamma H^2$. Subsequently, we explore the fundamental properties of the $f\left(Q\right)=Q-6\lambda M^2{\left(\frac{Q}{6M^2}\right)}^{\alpha }$ model and analyse the energy conditions to establish its validity. Our findings indicate that the introduced framework allows for the derivation of cosmological models that satisfy necessary energy constraints. Specifically, we show that the considered model enters the quintessence region for the equation of state parameter w, simultaneously violating the strong energy condition (SEC), leading to repulsive behaviour consistent with accelerated expansion. Thus, the introduced extension demonstrates potential for accurately describing cosmological models.

In this work we study static spherically symmetric solutions of effective field equations related to local and nonlocal higher-derivative gravity models, based on their associated effective delta sources. This procedure has been applied to generate modifications of the Schwarzschild geometry in several contexts (e.g., modified gravity, string theory, noncommutative geometry, generalized uncertainty principle scenarios), but a general analysis of the possible equations of state and their influence on the solutions was still lacking. Here, we aim to fill this gap in the literature and investigate whether these metrics might be able to reproduce features of the solutions of higher-derivative gravity models. In particular, we present an equation of state such that the solution matches the Newtonian-limit one in both regimes of large and small r. A significant part of the work is dedicated to studying the curvature regularity of the solutions and the comparison with the linearized solutions. Explicit metrics are presented for effective sources originating from local and nonlocal models. The results obtained here might be regarded as possible links between the previous research on linearized higher-derivative gravity and the solutions of the nonlinear complete field equations, which remain unknown at the moment.

A universal dual relation $T_0(n+1)=T_{HP}\left(n\right)$ between the minimum temperature ($T_0(n+1)$) black hole phase and Hawking-Page (HP) transition ($T_{HP}\left(n\right)$) black hole phase in two successive dimensions was introduced in [1], which was reminiscent of the AdS/CFT correspondence, as the HP transition temperature could be treated as the temperature of the dual physical quantity on the boundary and the latter corresponds to the one in the bulk. In this paper, we derive analytically the dual relations in Gauss-Bonnet (GB) gravity and GB-Maxwell gravity. For the GB (charged/uncharged) spherical AdS black holes, the dual relations are exactly the same with the ones in Einstein gravity. Especially for the GB hyperbolic AdS black holes, since there exist the HP transition with reentrance and triple points, the dual relations only hold while they characterize actually the duality between the (large/small) HP transition temperature and the extremum (minimum/maximum) temperature in two successive dimensions. In the grand canonical ensemble of GB gravity, the Gibbs energy has the similar qualitative behavior with the cases in the canonical ensemble of GB gravity, while there is an additional effect of electric potential on the HP transition. These dual relations are interesting in understanding the HP transition, and may bring some clue on the applications in the holographic principle and the black hole thermodynamics.

In this study, we examine the modular transformations of the (root-) T$\bar{\text{T}}$ deformed torus partition function of a two-dimensional CFT (with a gravitational anomaly) from the holographic perspective by computing the on-shell actions of various saddle solutions of the dual gravity theories.

It is known that the formation of a wormhole typically involves a violation of the Weak Energy Condition (WEC), but the reverse is not necessarily true. In the context of Brans-Dicke gravity, the generalized Campanelli-Lousto solution, which we shall unveil in this paper, demonstrates a WEC violation that coincides with the appearance of unbounded sheets of spacetime within the region where $0<r<r_{\text{s}}$. The emergence of a wormhole in the region where $r>r_{\text{s}}$ is thus only an indirect consequence of the WEC violation. Whereas the two regions, $0<r<r_{\text{s}}$ and $r>r_{\text{s}}$, in general are disconnected by physical singularities at $r=r_{\text{s}}$, they are both part of the same mathematical solution, and their behavior can provide insights into the WEC, which is a mathematical property of the solution. Furthermore, we utilize the generalized Campanelli-Lousto solution to construct a Kruskal-Szekeres diagram, which exhibits a “gulf” sandwiched between the four quadrants in the diagram, a novel feature in Brans-Dicke gravity. Overall, our findings shed new light onto a complex interplay between the WEC and wormholes in the Brans-Dicke theory.

In this paper, we study the thermodynamic properties and stability of static charged BTZ black holes with the inclusion of higher-order quantum corrections. The corrections to the entropy, mass, and Helmholtz free energy are derived, revealing the intricate interplay between quantum effects and classical gravitational forces in the context of black hole thermodynamics. The study of the specific heat capacity shows that higher-order corrections stabilize the system by removing the instabilities present at lower orders. The analysis of the van der Waals-like isotherms demonstrates the continuous transition from a highly compressible to an almost incompressible regime as the volume is decreased, akin to the behavior of supercritical fluids. Notably, the isotherms do not exhibit any regions of negative compressibility, indicating the absence of instabilities. Furthermore, the convexity of the Helmholtz free energy as a function of volume confirms the stability of the charged BTZ black hole system. These findings provide valuable insights into the complex thermodynamic landscape of three-dimensional black holes and the role of quantum corrections in shaping their behavior.

We construct an integrable sigma model with a generalized $F$ structure, which involves a generalized Nijenhuis structure $J$ satisfying $J^3=-J$. Utilizing the expression of the generalized complex structure on the metric Lie group manifold G in terms of operator relations on its Lie algebra $g$, we formulate a Yang-Baxter sigma model with a generalized complex structure. Additionally, we present multi-Yang-Baxter sigma models featuring two and three compatible Nijenhuis structures. Examples for each of these models are provided.