International Journal of Modern Physics D

The preface to the special issue of Int. J. Mod. Phys. D “New trends in Cosmology, Particle Physics and Astrophysics” briefly reviews some new ideas in the development of Modern Astrophysics, Cosmology, Particle and Astroparticle Physics inspired by discussions at the Sixth International Conference on Particle Physics and Astrophysics (ICPPA2022).

In this paper, we study spin effects in the neutrino gravitational scattering by a supermassive black hole with a magnetized accretion disk having a finite thickness. We exactly describe the propagation of ultrarelativistic neutrinos on null geodesics and solve the spin precession equation along each neutrino trajectory. The interaction of neutrinos with the magnetic field is due to the nonzero diagonal magnetic moment. Additionally, neutrinos interact with plasma of the accretion disk electroweakly within the Fermi approximation. These interactions are obtained to change the polarization of incoming neutrinos, which are left particles. The fluxes of scattered neutrinos, proportional to the survival probability of spin oscillations, are derived for various parameters of the system. In particular, we are focused on the matter influence on the outgoing neutrinos flux. The possibility to observe the predicted effects for astrophysical neutrinos is briefly discussed.

The observable inflation is a final step in a slow evolution of our space. The latter occurs starting from the Planck scale, so that eventually a huge number of causally disconnected regions of space (pocket universes) will appear. The Multiverse thus formed consists of similar universes and, therefore, does not fulfill its mission. Here, we discuss the way to improve the situation. We study the effect of the quantum fluctuations at high energies on the shape of compact extra dimensions which turn out to be specific to each pocket universe. Low-energy physical parameters depend on extra dimensional metric. Therefore, the low-energy physics is different in different pocket universes. The numerical estimation of the probability of finding a particular metric is based on the model of compact two-dimensional extra space.

The question about the appearance of time in the semiclassical limit of quantum gravity continues to be discussed in the literature. It is believed that a temporal Schrödinger equation for matter fields on the background of a classical gravitational field must be true. To obtain this equation, the Born–Oppenheimer approximation for gravity is used. However, the origin of time in this equation is different in works of various authors. For example, in the papers of Kiefer and his collaborators, time is a parameter along a classical trajectory of gravitational field; in the works of Montani and his collaborators, the origin of time is introducing the Kuchař–Torre reference fluid; in the extended phase space approach, the origin of time is the consequence of existing of the observer in a fixed reference frame. We discuss and compare these approaches. To make the calculations transparent, we illustrate them with the model of a closed isotropic universe. In each approach, one obtains some Schrödinger equation for matter fields with quantum gravitational corrections, but the form of the equation and the corrections depend on additional assumptions which are rather arbitrary. None of the approaches can explain how time had appeared in the Early Universe, since it is supposed that classical gravity and, therefore, classical spacetime had already come into being.

General relativity (GR) passed many astronomical tests but in majority of them GR predictions have been tested in a weak gravitational field approximation. Around 50 years ago a shadow was introduced by Bardeen as a purely theoretical concept but due to an enormous progress in observational and computational facilities this theoretical prediction has been confirmed and the most solid argument for an existence of supermassive black holes in Sgr A^* and M87^* has been obtained.

Stable multiple charged particles can possess electroweak charges, as per the walking technicolor models. An asymmetry of these particles is balanced by sphaleron transitions which among other things can provide an excess of baryons and/or leptons. A possibility to generate sufficient amount of particles with the charge $-2n$ to explain the observed dark matter density by dark atoms (which are bound states of multiple charged techniparticles with n helium nuclei) is considered in the framework of thermodynamic approach.

In this paper, we review the theoretical basis for generation of gravitational waves and the detection techniques used to detect a gravitational wave. To materialize this goal in a thorough way, we first start with a mathematical background for general relativity from which a clue for gravitational wave was conceived by Einstein. Thereafter, we give the classification scheme of gravitational waves such as (i) continuous gravitational waves, (ii) compact binary inspiral gravitational waves and (iii) stochastic gravitational wave. Necessary mathematical insight into gravitational waves from binaries is also dealt with which follows detection of gravitational waves based on the frequency classification. Ground-based observatories as well as space borne gravitational wave detectors are discussed in a length. We have provided an overview on the inflationary gravitational waves. In connection to data analysis by matched filtering there are a few highlights on the techniques, e.g. (i) random noise, (ii) power spectrum, (iii) shot noise and (iv) Gaussian noise. Optimal detection statistics for a gravitational wave detection is also in the pipeline of the discussion along with detailed necessity of the matched filter and deep learning.

In this paper, we present the historical background of the Thirty-Meter Telescope at Mount Mauna Kea and a few facts regarding scientific advancement. However, we will not focus on any politically motivated matters and ethical issues, rather our sincere concern is to highlight the overall history, philosophy, science and technology which have prevailed for any civilized advancement of the society.

Dilaton and axion are ubiquitous in extended supergravities and closed superstrings. We propose new models of modular inflation in four-dimensional $N=1$ supergravity coupled to the chiral dilaton–axion–goldstino supermultiplet, which fit some necessary conditions of superstring cosmology. The model parameters are tuned to obey precision measurements of the cosmic microwave background radiation. We employ the modular-invariant superpotentials and asymptotically modular-invariant Kähler potentials, and achieve axion stabilization with high-scale supersymmetry breaking.

In this paper, we proposed a generalized Lagrangian for three different classes of scalar fields namely quintessence ($\alpha =-1$), phantom ($\alpha =0$) and tachyonic ($\alpha =1$) parameterized by $\alpha$. These three scalar fields can be described by a common single Lagrangian called generalized scalar field Lagrangian (GSL). We obtain mathematically consistent forms of generalized equations of motion parameterized by $\alpha$. It can recover the individual equation of motion of quintessence, phantom and tachyon scalar fields from generalized equation of motion of the unified scalar field.

In this paper, we revise dynamical constraint on primordial black hole (PBH) abundance following the effect of their interaction with stellar cluster in dwarf galaxy Eridanus II in case of PBH clustering. We consider scattering of stars on PBH cluster as a whole, dynamical friction of stars inside cluster and finally we are taking into account tidal forces’ effects due to the finite size of PBH cluster. We obtain the rate of change of kinetic energy of the stars and PBHs to make conclusion about constraints on clusters.