Field transformation rules of the standard fermionic T-duality require fermionic isometries to anticommute, which leads to complexification of the Killing spinors and results in complex valued dual backgrounds. We generalize the field transformations to the setting with non-anticommuting fermionic isometries and show that the resulting backgrounds are solutions of double field theory. Explicit...
Horndeski theories [1]
\begin{align}
&S=\int\mathrm{d}^4x\sqrt{-g}\left(\mathcal{L}2 + \mathcal{L}_3 + \mathcal{L}_4 + \mathcal{L}_5 + \mathcal{L{BH}}\right),\
&\mathcal{L}2=F(\pi,X),\
&\mathcal{L}_3=K(\pi,X)\Box\pi,\
&\mathcal{L}_4=-G_4(\pi,X)R+2G{4X}(\pi,X)\left[\left(\Box\pi\right)^2-\pi_{;\mu\nu}\pi^{;\mu\nu}\right],\
...
The main subject of study in the general relativity and other branches of science is the geometry of (pseudo)-Riemannian spaces defined by a metric. To better imagine and understand the properties of a particular spacetime, it is often useful to define a surface in some ambient space that has such a metric - in other words, to construct an isometric embedding. However, the search for an...
The usual Vaidya spacetime may be extended to include both null dust and null string fluids leading to the generalised Vaidya spacetime. Nowadays, this metric is widely used to describe the gravitational collapse, a radiating star with a generalised Vaidya atmosphere, black holes in dynamical cosmology backgrounds. In our work we consider horizon structure of this spacetime. We have calculated...
We considered the Tsallis holographic dark energy model in frames of Nojiri-Odintsov gravity with $f(R)=R+\lambda R^2-\sigma{\mu}/{R}$. The equations describing the cosmological evolution in this case contain third derivative of the scale factor on time. Therefore this requires to impose initial condition on the second derivative $a$ (which is equivalent to the condition on $\dot{H}(0)$). The...
Penrose process states that due to collision or decay there might be particles with negative energy in the ergosphere of a rotating black hole. Recently, the analogue of this process has been found for charged particles in Reissner-Nordstrom spacetime.
In this work the Penrose process is considered for charged particles in charged Vaidya spacetime. This metric is dynamical one with mass and...
We consider dynamics of the massive minimally coupled scalar field theory in an expanding Friedmann-Lemaitre-Robertson-Walker universe. We consider the standard toy model of the conformally flat space-time where the conformal factor becomes constant at the distant past and the distant future. Employing Schwinger-Keldysh diagrammatic technique, we compute infrared loop corrections to the...
Cosmological particle creation: Weyl geometry + Scalar field
Victor Berezin
Institute for Nuclear Research of the Russian Academy of Sciences,
60th October Anniversary Prospect 7a, 117312 Moscow, Russia
E-mail: berezin@inr.ac.ru
Abstract
We investigated the possibility of the homogeneous and isotropic...
One of the ways to study the space near a black hole is to study the behavior of a test body in its gravitational field. In this paper, we consider the deviation of geodesics, which is physically responsible for the tidal forces acting on a body in the field of a rotating black hole. The modified geodesic deviation equation in the curved space-time of a axially-symmetric Kerr black hole is...
We describe thermodynamics properties and Hawking-Page phase transition of the Schwarzschild black hole in the Anti-de Sitter-Beltrami (SAdSB) spacetime.
We discuss the Beltrami or inertial coordinates of the Anti-de Sitter(AdS) spacetime. Transformation between the non-inertial and inertial coordinates of the AdS spacetime is introduced to construct the solution of spherical gravitating mass...
In the last decade, de Sitter (dS) and Anti-de Sitter (AdS) spacetimes have generated a lot of interest. This led to the creation of a new kinds of Special Relativity (SR), the so-called dS-SR and AdS-SR: relativity with dS(AdS) radius $R$. The existence of inertial frames of reference and inertial coordinate systems are the keystones of the SR. It can be proved by direct calculations that the...
Recent works have explored interesting phenomena about quantum field theory in de Sitter space. One of the simple ways to estimate the behaviour of a system with matter in an external electric or gravitational field is to calculate the effective equation of motion for small perturbations of a background field in one-loop order. Further approximations allow us to introduce the notion of Debye...
According to the Penrose process there might be particles with negative energy in the ergosphere of a rotating black hole. Later, it was shown that there might be also particles with zero energy but with not zero angular momentum. In this work we consider properties of such particles. In particular, we investigate the question about the inertial forces for such particles in equatorial plane...
We consider a massive scalar field theory on static four-dimensional space-times with horizons. We study the near horizon behaviour of the quantum expectation values of the stress--energy tensor operator for the thermal states with arbitrary temperatures. It turns out that the dependence of the expectation values on the temperature and tensor structure of the stress--energy tensor are...
A phenomenological description of the process of particle production is explored on the example of the action of an ideal fluid with a variable number of particles. The Euler formalism is used because it allows to include the continuity equation in the matter action explicitly through a corresponding constraint. To pass to a model with a variable number of particles, it suffices to replace the...
We investigate the free energy and entropy of the Gaussian massive scalar field theory in the static de Sitter space-time for arbitrary temperature.There are two types of contributions to the free energy: one is of the "area type" and can be attributed to the horizon, while the other is of the "volume type" and is associated with the interior of the space-time. The latter contribution in the...
At the moment one the most prominent sign of the new physics beyond SM and GR is dark matter phenomenon. Despite large number of theories built to describe it, still none succeed. Simple models, that are able to explain observational data are of special interest. One of the recent models of this kind is mimetic gravity proposed by A. Chamseddine and V. Mukhanov. This theory describes dark...
We examine the Chandrasekhar limit for white dwarfs in $f(R)$
gravity, with a simple polytropic equation of state describing
stellar matter. We use the most popular $f(R)$ gravity model,
namely the $f(R)=R+\alpha R^2$ gravity, and calculate the
parameters of the stellar configurations with polytropic equation
of state of the form $p=K\rho^{1+1/n}$ for various values of the
parameter $n$....
An approach is developed in the embedding theory, which considers the theory from a position close to the mimetic gravity. In this approach, there is a class of solutions in which the equations of motion of the theory in the nonrelativistic approximation describe general relativity with additional matter, which is close in properties to dust-like matter but has some complex self-interaction....
There is a famous theorem that Black holes don't have hairs. It means what, a black hole has three charges, i.e. mass, angular momentum, and electric charge. However, Hawking showed that black hole can possess so could soft hair. Another method to evade no hair theorem is gravitational decoupling. Applying this method one can obtain hairy Schwarzschild, Reissner-Nordström, Kerr black holes....
Уравнения теории вложения мы линеаризуем относительно фона, который представляет собой прямое произведение прямой по времени на нетривиальное плоское вложение трёхмерного многообразия. Такого рода приближение является специальным случаем предела слабого гравитационного поля в теории вложения. Линеаризованные уравнения при этом совпадают с 6 из 10 линеаризованными уравнениями Эйнштейна. Главное...
