Studying the flat limit of AdS/CFT is an important task that aims to make contact with flat-space scattering, BMS symmetries, and ultimately the physics of our universe. A particularly interesting low-energy corner of the holographic principle is the fluid/gravity correspondnce which connects the dynamics of long-wavelength perturbations in AdS space to the one of a relativistic conformal...
We consider different types of reducibility of a matrix $n\times n$ intertwining operator and reveal criterion for regular reducibility. It is shown that in contrast to the scalar case $n = 1$ there are for any $n\geqslant 2$ regularly absolutely irreducible matrix intertwining operators of any order $N\geqslant 2$, i.e. operators which cannot be factorized into a product of a matrix...
We construct an analogue of Yang--Baxter deformations defined by a single Killing vector, that is a solution generating transformation in Einstein--Maxwell dilaton theory. We show that these are nothing but a coordinate transformation in a parent theory related to EMd theory by KK reduction. Similarly (almost-abelian) bi-vector Yang--Baxter deformations are coordinate transformations in the...
Quench is an abrupt change in a system's parameters. In the quantum context, it can be viewed as a perturbation of the initial state of a quantum field theory relative to a known density matrix, such as that for the vacuum state or a finite-temperature state. Within the framework of the inflationary model of the early universe, a quantum quench can be used to study the system's evolution...
We present and study new nontopological soliton solutions in the U(1) gauged nonlinear O(3) sigma-model with a symmetry breaking potential in 3+1 dimensional space-time. The configurations are endowed with an electric and magnetic field and also carry a nonvanishing angular momentum density. We discuss properties of these solitons and investigate the domains of their existence. The negative...
A topological geon is an asymptotically (anti-)de Sitter or flat spacetime with topology $\mathbb{R}\times{}M$, where $M$ is the punctured projective space, $M=\mathbb{R}P^3\,\backslash\{p\}$, and the removed point $p$ corresponds to the spacelike infinity. The spacelike slice $M$ is conventionally obtained as the quotient $W/\mathbb{Z}_2$ of a symmetric wormhole $W$ by the isometric action of...
We study a novel variation of the large D limit in which s-wave sector is described by a 2D gravity nearly decoupled from other modes, but temperature remains finite. We discuss the quantum description of such system and it's thermal behavior
A black hole can evaporate through the mechanism proposed by Hawking. In the case of a Schwarzschild black hole, this leads to the temperature of the black hole increasing without bound as its mass decreases. However, if the black hole possesses multiple horizons, as in the case of regular black holes, the picture changes dramatically. In our work, we analyze the behavior of the Hawking...
Coexistence of heavy particles and primordial black holes in early Universe can result in baryon asymmetry production. It requires C and CP symmetries violation of particles scattering on relativistic symmetric plasma. Generation mechanism is considered with including expansion effects. Several possible realizations can be considered with different resulting asymmetry and available parameters space.
We perform numerical semiclassical calculations of the false vacuum decay probability for a scalar field in the Schwarzschild spacetime. The suppression $F$ of the decay probability $P \sim e^{-F}$ is given as a functional of a semiclassical solution. That solution is defined on a certain contour in complex time. We consider a model with potential $V(\phi) = \frac{1}{2}m^2 \phi^2 - \frac{1}{2}...
Models of black holes that differ from idealized vacuum and electrovacuum solutions of Einstein's equations often contain parameters whose physical interpretation is unclear. However, to propose a black hole model for experimental verification, we must clearly understand which parameters describe the black hole and what physical constraints can be imposed on each parameter. When considering...
In this talk, we will explore the dynamics of entanglement entropy and entanglement islands within a two-sided Reissner-Nordström black hole placed in a cavity bounded by a reflecting wall. This setup alters the dynamics of entanglement entropy, causing it to saturate at a value that is potentially lower than the thermodynamic entropy of the black hole, which contradicts the Page curve...
Pseudoscalar particles called axions are promising candidates for dark matter constituents [1]. The hypothetical interaction of axions with leptons (e.g., electrons) produces an effective electron-electron interaction. When considering electrons in hexatomic molecules, e.g., RaOCH$_3$, such interaction via axion exchange is capable of violating the parity parity of molecular Hamiltonian. Thus,...
Features of deviation of circular trajectories in the central field in non-relativistic and relativistic cases are investigated. All potentials for which perturbed trajectories in the non-relativistic case are closed and asymptotically flat spherically symmetric metrics with closed perturbed orbits are found. It is shown that in the general theory of relativity there are metrics in which the...
The standard non-renormalizable action of quantum gravity without the contribution of matter
\begin{equation}
S = \frac{1}{2\kappa} \int d^4x \sqrt{-g} \left( R - 2\Lambda \right).
\end{equation}
is investigated.
Dimensional analysis, generally accepted in the study of continuous phase transitions in statistical physics, has obtained and the infrared-effective action for describing...
Isometric embedding of a pseudo-Riemannian spacetime is a description of this spacetime as a surface in an ambient spacetime of higher dimension. This procedure has been used for more than a century in the examination of solutions of Einstein equations, since the embedding class (i.e. the minimal codimension of a surface in a flat ambient spacetime) is an invariant characteristic of a...
The application of the Horndeski theory in late-time cosmology is strongly limited by the strict coincidence of the propagation speeds of gravitational and electromagnetic waves. This restriction assumes that a photon with minimal coupling is not modified even at scales at which General Relativity (GR) may need modification. We have shown that the four-dimensional Galileon, obtained as a...
In this talk, I will focus on non-singular solutions that can be realized within Horndeski theories, whose distinctive structure allows for controlled violations of energy conditions without introducing pathologies. I will review the typical stability challenges that arise at the level of linear perturbations and highlight how they constrain such solutions. Finally, I will discuss illustrative...
We discuss latest results on Kaluza-Klein compactifications of Horndeski-type theories (beyond Horndeski and DHOST included). We show the subclass of such theories that obeys principal phenomenological constraints for dark energy models.
We investigate the possibility of addressing the cosmological constant problem through a self-tuning mechanism within the framework of beyond Horndeski theory. In particular, we propose a cosmological scenario in which self-tuning operates during inflation but switches off prior to reheating, while leaving behind the correct dark energy density. Furthermore, we explore the use of self-tuning...
We consider a class of two-dimensional dilaton gravity models with linear dilaton vacuum including Callan-Giddings-Harvey-Strominger (CGHS) model as the special case. General thermodynamic properties of black holes in such models are evaluated. We focus on the CGHS model and its modification with regular black holes as empty-space solutions characterized by ever-present finite curvature. We...
