The formation of spectral-spatial distortions of cosmic microwave background radiation near primordial black holes at redshifts 100-1000 is considered. After hydrogen recombination, the radiation from these objects leads to the significant increase in the population of the hydrogen subordinate levels in their surrounding environment. Consequently, this allows for the observation of a...
Primordial black hole (PBH) production is investigated in a chaotic inflation model with a massive inflaton whose potential $V_0 + m^2\varphi^2/2$ contains a localized bump. The presence of the bump temporarily slows down the inflaton motion and leads to high, narrow peaks in the density perturbation spectrum. The density perturbation spectrum and the resulting PBH mass function are calculated...
Black holes formed in the early Universe (primordial black holes, PBHs) may simultaneously explain several astrophysical anomalies. These include, for example, the existence of supermassive black holes in the young Universe ($z>6$, [Mazzucchelli C. et al., (2017, ApJ)][1]) and black holes with masses of $\sim30 M_\odot$ detected by gravitational-wave observatories ([LVK Scientific...
One possible mechanism for the formation of primordial black holes (PBHs)
is the collapse of domain walls. Previous theoretical models considered PBH
formation in the spherical approximation, whereas full field-theoretic
simulations of non-spherical domain walls clusters are too computationally
demanding to accumulate sufficient statistics.
In this work, we derive the equations of motion...
The interaction of a closed domain wall with the primordial plasma during the radiation-dominated stage of the Universe is studied. When the plasma temperature drops below a threshold value determined by the wall potential parameters, the wall becomes opaque, trapping plasma inside. Relativistic hydrodynamic simulations of the trapped plasma and the wall dynamics are performed. The criterion...
A dynamical mechanism for vacuum energy compensation in both de Sitter (dS) and anti-de Sitter (AdS) space-times is discussed. The proposed cosmological model relies on a non-minimal coupling between a scalar field and the curvature scalar. We demonstrate that this mechanism efficiently eliminates huge initial vacuum energies (both positive and negative), dynamically driving the curvature...
Possible corrections to cosmological inflation models based on scalar-tensor gravity are considered. The influence of non-minimal coupling between a scalar field and curvature on cosmological dynamics and parameters of cosmological perturbations is examined, with particular emphasis on corrections arising from a specific parametrization of this coupling.
Cosmological models based on...
Ricci–Gauss–Bonnet–Weyl (RGW) gravity, based on a pure geometric Lagrangian defined by a specific combination of the Ricci (R), Gauss–Bonnet (G), and Weyl (W) scalars, is proposed and discussed as a potentially viable generalization of General Relativity (GR) for cosmology, astrophysics, and the Solar System. In this RGW gravity, there are no ghosts or unstable perturbations. Within the...
Constructing physically viable models within Horndeski and Beyond Horndeski theories requires strict checks to avoid ghost and gradient instabilities, yet the corresponding stability constraints for dynamical spherically symmetric backgrounds remain incomplete. Previous studies of perturbations over such backgrounds focused exclusively on the odd-parity sector, which yields stability...
This work investigates the physical stability of cosmological bounce scenarios. As a starting point, we consider a previously proposed bounce solution for a homogeneous and isotropic background within a subclass of Horndeski theory. In this model, the scalar perturbation mode is non-dynamical ("frozen"), which allows the system to formally evade standard no-go theorems limiting the...
Bouncing cosmologies and Galilean Genesis provide alternative scenarios to the standard inflationary paradigm. An important question for such models is whether their characteristic cosmological backgrounds exhibit dynamical attractor behaviour, making their evolution insensitive to a broad class of initial conditions. In this talk, I will discuss the attractor properties of bouncing and...
We develop a manifestly conformal-frame-independent approach to assessing perturbative unitarity and apply it to modified Genesis in a $G_2+G_3$ Horndeski model. The construction uses an effective metric determined by the tensor quadratic action, its associated conformal time, and canonically normalized scalar perturbations. We determine the quadratic coefficients and scalar sound speed,...
We consider particle creation of a non‑conformal scalar field in the Early Universe. The deviation from conformality is assumed to be small, which allows us to treat the terms describing the non-conformal scalar field as a perturbation. We derive the Schrödinger equation for the system of gravitational and scalar fields from the path integral making use of a holomorphic representation for the...
We study scalar particle production in a closed isotropic universe within the extended phase space approach. Unlike the treatments in which the gravitational field is treated classically, we quantize the coupled gravitational and matter degrees of freedom and derive the Schrodinger equation for the wave function of the Universe, including perturbative contributions associated with a slight...
We consider a dilatonic dyon black hole solution
with a gravitational radius of $2 \mu$ and two charges,
$Q_1$ (electric) and $Q_2$ (magnetic), within the framework
of a four-dimensional gravitational model comprising one scalar field and one 2-form. The dilaton coupling constant $\lambda$ is fixed by $\lambda^2 = \frac{3}{2}$. This solution is related to the $A_2$ Toda chain.
The...
We explore the quasinormal modes of a massless test scalar field in the gravitational background of a non-extremal dilatonic dyonic black hole. The dyon-like black hole solution is considered within a four-dimensional gravitational model that includes two scalar fields and two 2-forms.
It is governed by two dilatonic coupling vectors (\vec{\lambda}_s) (with (s=1,2)) that satisfy...
We present a new gravitational framework in which the conventional conservation of the energy-momentum tensor is relaxed and replaced by a non-conservation law motivated by relativistic thermodynamics. In this approach, the exchange of energy and momentum between matter and the gravitational sector is treated as a fundamental physical effect rather than as an effective description of an...
Spatial anisotropy of the gravitational constant $G$ is a key prediction of the Spin-Density Model (SDM), in which space-time is considered as a dynamic carrier medium. According to the SDM, large-scale polarization of this medium by active galactic nuclei leads to a dependence of the effective gravitational constant on direction, manifesting as a difference in gravitational attraction in the...
We present the Dark Energy Survey Year 6 3x2pt analysis, which combines cosmic shear, galaxy clustering, and galaxy-galaxy lensing measurements across ~4000 deg². Using an unprecedented sample of lens and source galaxies, this study delivers some of the most precise constraints to date on key cosmological parameters, including the matter density Ωₘ and the amplitude of cosmic structure σ₈. Our...
In the Bergmann-Wagoner-Nordtvedt class of scalar-tensor theories, well known are wormhole solutions existing in the phantom sector of the theory. Exceptional wormholes exist in the canonical sector owing to the phenomenon of conformal continuation, the situation where the Einstein frame manifold maps to only a region of the Jordan frame manifold, and the latter is smoothly continued to a...
We present simulated detectability of traversable wormholes (WHs) in wide binary astrophysical systems without accretion (dormant binary systems) and in the Galactic center. The wormhole spacetime is represented as a gluing of two asymptotically flat Schwarzschild spacetimes, without specifying the detailed geometry of the throat. We consider a traversable WH candidate as a compact object in a...
We study the neutrino sector of an eight-dimensional two-brane model based on $f(R)$ gravity. The metric is warped:
$ds^{2} = e^{2\gamma(u)}\eta_{\mu\nu}dx^{\mu}dx^{\nu} - du^{2} - r^{2}(u)\,d\Omega^{2}_{n-1}.$
Here $u$ is the radial extra coordinate, and the remaining three coordinates parametrise a compact internal manifold. The classical field equations admit a countable family of...
The standard cosmological model $\Lambda\mathrm{CDM}$, successfully describes large-scale structure of the Universe. However, several problems on galactic scales motivate studies of alternative dark matter (DM) models. One of such models is self-interacting dark matter (SIDM), where interactions between DM particles can change the internal structure of DM halos.
In previous studies, our...
Matter consists of particles and fields, and more consistently only of quantum fields. Particles are the localized excitations of quantum fields. Sometimes fermions are called matter’’ and bosons are calledfields’’. Definition: the component of the Universe is called ``dark’’ if it does not emit the light.
{\bf Basic components of observable Universe}:
70\% is the `dark field’ or...
