We discuss some properties of recently proposed models a ghost-free gravity. For this purpose we study solutions linearized gravitational equations in the framework such theory. mainly focus on version theory with exponential modification exp(□/μ 2)□−1 free propagator. The following three problems are discussed: (i) field point mass; (ii) Penrose limit source boosted to speed light; and (iii) spherical collapse null fluid. first problem demonstrate that it can be solved by using method heat...

We study linearized equations of a ghost-free gravity in four- and higher-dimensional spacetimes. consider versions such theory where the nonlocal modification $\Box$ operator has form $\Box \exp[(-\Box/\mu^2)^N]$, $N=1$ or $N=2n$. first obtain Newtonian gravitational potential for point mass models demonstrate that it is finite regular any number spatial dimensions $d\ge 3$. The second result paper calculation field an ultrarelativistic particle theories. And finally, we head-on collision...

The problem of the vacuum polarization conformal massless fields in static space-times is considered. A tensor ${T}_{\ensuremath{\mu}\ensuremath{\nu}}$ constructed from curvature, Killing vector, and their covariant derivatives proposed which can be used to approximate average value stress-energy 〈T${^}_{\ensuremath{\mu}\ensuremath{\nu}}$${〉}^{\mathrm{ren}}$ such spaces. It shown that if (i) its trace T $_{\ensuremath{\epsilon}}^{\ensuremath{\epsilon}}$ coincides with anomaly 〈T^...

The vacuum polarization of the massive scalar, spinor, and vector fields in Kerr spacetime is investigated. explicit expression for expectation value energy-momentum tensor obtained its properties are discussed.

In this paper we study quantum radiation from an evaporating spherically symmetric non-singular black hole. We used a modified Hayward metric for description of assume that the mass parameter depends on advanced time, and choose dependence so it properly reproduces both hole formation its subsequent evaporation. consider massless scalar field propagating in geometry use 2D approximation calculation average stress-energy tensor. For quantity is sufficient to find map between Killing times...

We study the gravitational field of static p-branes in D-dimensional Minkowski space framework linearized ghost-free (GF) gravity. The concrete models GF gravity we consider are parametrized by non-local form factors $\exp(-\Box/\mu^2)$ and $\exp(\Box^2/\mu^4)$, where $\mu^{-1}$ is scale non-locality. show that singular behavior General Relativity cured short-range modifications introduced non-localities, derive exact expressions regularized fields, whose geometry can be written as a warped...

Abstract It is shown that the usual characteristics of a black hole and physical fields produced by it obtain unified geometrical meaning in five‐dimensional framework. Especially, demonstrated solution for rotating with electric scalar charges can be generated boost transformation fifth coordinate from Kerr solution.

Abstract We analyze the angular momentum balance for a particle undergoing Thomas precession. The relationships among relativistic torque, center of mass, and inertia spinning are clarified. show that spin precession is accompanied by orbital precession, present examples resulting out-of-plane motion.

Recently it was proposed to explain the dynamical origin of entropy a black hole by identifying its degrees freedom with physical modes propagating in interior. The present paper contains further development this approach. no-boundary proposal (analogous cosmological wave function) is put forward for pure quantum state hole. This functional on configuration space fields (including gravitational one) inhabiting three-dimensional Einstein-Rosen bridge topology. For linearized field...

The authors examine 't Hooft's prescription (1985) for cutting off eigenmodes of particle wavefunctions in the vicinity black hole event horizons N dimensions. They find any N>3 that cutoff occurs as a consequence causal structure spacetime independently strength source, agreement with four-dimensional case. separately discuss special case N=2, showing why this depends on source.

Different methods of calculation quantum corrections to the thermodynamical characteristics a black hole are compared. The general relation between on-shell and off-shell approaches is discussed. We consider simplified 2D model with dilaton gravity show in its framework that observable entropy can be presented form ${S}^{\mathrm{TD}}=\ensuremath{\pi}{\overline{r}}_{+}^{2}+{S}^{\mathrm{SM}}\ensuremath{-}{S}_{\mathrm{Rindler}}^{\mathrm{SM}}$. Here, ${\overline{r}}_{+}$ radius horizon shifted...

Massless and massive scalar fields massless spinor are considered at arbitrary temperatures in four dimensional ultrastatic curved spacetime. Scalar models under consideration can be either conformal or nonconformal include self-interaction. The one-loop nonlocal effective action finite temperature free energy for these quantum found up to the second order background field strengths using covariant perturbation theory. resulting expressions of infrared divergences. Spectral representations...

The metric ansatz is used to describe the gravitational field of a beam-pulse spinning radiation (gyraton) in an arbitrary number spacetime dimensions D. First we demonstrate that this belongs class metrics for which all scalar invariants constructed from curvature and its covariant derivatives vanish. Next, it shown vacuum Einstein equations reduce two linear problems (D-2)-dimensional Euclidean space. first find static magnetic potential created by point-like source. second requires...

We study radiation emitted by a time-dependent source of scalar massless field in the framework ghost-free modifications theory. consider simple model emitter: namely, we assume that it is point-like and monochromatic. focus on most common versions theory, where propagator ${\ensuremath{\square}}^{\ensuremath{-}1}$ modified as follows: $\mathrm{exp}(\ensuremath{-}(\ensuremath{\square}/{\ensuremath{\mu}}^{2}{)}^{N}){\ensuremath{\square}}^{\ensuremath{-}1}$, $\ensuremath{\mu}$ characteristic...

We discuss the quantum-mechanical scattering of a massless scalar field on δ-potential in ghost-free theory and obtain analytic solutions for coefficients. Due to non-locality transmission coefficient tends unity frequencies much larger than inverse scale non-locality, even infinitely strong potentials. At same time there exists critical strength barrier below which is always frequency that totally reflected. These properties theories are quite generic distinguish them from local theories....

An expectation value of a stress-energy tensor nonconformal massless scalar field in background geometry cosmic string and at finite temperature is calculated. The result applicable to arbitrary values an angle deficit temperature.

A massless scalar field minimally coupled to gravity and propagating in Schwarzschild spacetime is considered. After dimensional reduction under spherical symmetry the resulting 2D theory canonically quantized renormalized expectation values $〈{T}_{\mathrm{ab}}〉$ of relevant energy-momentum tensor operator are investigated. Asymptotic behaviors analytical approximations given for Boulware, Unruh Hartle-Hawking states. Special attention devoted black-hole horizon region where WKB...

We study the gravitational field of a spinning radiation beam pulse (a gyraton) in $D$-dimensional asymptotically AdS spacetime. It is shown that Einstein equations for such system reduce to set two linear $(D\ensuremath{-}2)$-dimensional space. By solving these we obtain metric which an exact solution with (negative) cosmological constant. The explicit metrics $4D$ and $5D$ gyratons spacetime are given their properties discussed.