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Yuri N. Obukhov

Publications and source records attributed to Yuri N. Obukhov.

At least 19 recordsLinked to original sources

Rotation of the polarization plane in axion fields: application to neutron star polar cap regions

We study observable manifestations of an axion field, focusing on possible polarizational effects for electromagnetic wave propagating in such a special magnetoelectric medium. The corresponding analysis is based on a geometric model of the Casimir type, in the framework of which the rotation angle of the polarization plane is derived to the lowest order. The results obtained are discussed for astrophysical conditions of a neutron star, where an existence of a locally inhomogeneous axion region is predicted in the polar cap.

hep-ph↗

Dynamic effects of external axion fields in a system of many particles with spin

We develop the theoretical model that describes dynamic non-equilibrium effects of external inertial and axion fields in a system of particles with spin. The possibility of using the spin density and the current density of non-relativistic quantum particle systems for the detection of the hypothetical axion-like dark matter is discussed. The resulting closed system of dynamic equations encompasses the continuity equation, the momentum balance equation, and the spin density evolution equation, accounting for the influence of the spin-rotation coupling and the external axion fields. The new formalism opens up new perspectives for an experimental search of dark matter axions.

hep-th↗

Cosmographic constraints on a Gödel-type rotating universe

We investigate the possibility of global cosmic rotation using a Gödel-type rotating cosmological model, constrained through a cosmographic analysis of Type Ia supernovae (SNIa) from the Pantheon+ dataset. Employing a Taylor-expanded apparent magnitude--redshift relation derived via the Kristian-Sachs formalism, we analyze low-redshift SNIa data across five redshift bins (up to $Z \leq 0.5$). Our results reveal a mild but consistent preference for cosmic rotation, with the dimensionless rotation parameter $Ω_0$ peaking at $0.29^{+0.21}_{-0.15}$ for $Z \leq 0.2$, and a broadly aligned anisotropy axis centered around equatorial coordinates $(243^\circ, -49^\circ)$. The inferred Hubble constant $h_0 \approx 0.73$ remains stable across all bins, while the deceleration parameter $q_0$ trends from near-zero to mildly negative values with increasing redshift. Model comparison using the Akaike Information Criterion (AIC) indicates a statistically significant preference for the rotating model over the standard $Λ$CDM cosmology at intermediate redshifts. These findings suggest that cosmic rotation, if present, may influence the late-time expansion history of the universe and warrants further investigation beyond the cosmographic regime.

astro-ph.CO↗

Spin-of-Light Gyroscope and the Spin-Rotation Coupling

We discuss the coupling of photon spin with rotation in connection with a recent proposal of Fedderke et al. [arXiv:2406.16178 [physics.optics]] regarding a precision gyroscope based on the intrinsic spin of light. To this end, we analyze the propagation of electromagnetic radiation in a physical system that uniformly rotates about the direction of wave propagation in the presence of an ambient medium. Finally, we consider the possibility of using this type of spin-of-light gyroscope to measure gravitomagnetic fields.

quant-ph↗

Violating Lorentz invariance minimally by the emergence of nonmetricity? A Perspective

Lorentz invariance belongs to the fundamental symmetries of nature. It is basic for the successful Standard Model of Particle Physics. Nevertheless, within the last decades, Lorentz invariance has been repeatedly questioned. In fact, there exist different research programs addressing this problem. We argue that a most adequate understanding of a possible violation of Lorentz invariance is achieved in the framework of the gauge-theoretic approach to gravity: a non-vanishing nonmetricity of a metric-affine geometry of spacetime heralds the violation of the Lorentz symmetry.

gr-qc↗

Search for manifestations of spin-torsion coupling

We investigate the axial vector torsion-spin coupling effects in the framework of the Poincaré gauge theory of gravity with the general Yang-Mills type Lagrangian. The dynamical equations for the ``electric'' and ``magnetic'' components of the torsion field variable are obtained in the general form and it is shown that the helicity density and the spin density of the electromagnetic field appear as the physical sources. The modified Maxwell's equations for the electromagnetic field are derived, and the electromagnetic wave propagation under the action of the uniform homogeneous torsion field is considered. We demonstrate the Faraday effect of rotation of the polarization for such a wave, and establish the strong bound on the possible cosmic axial torsion field from the astrophysical data.

gr-qc↗

Spacetime geometry from Dirac spinor theory

The quintet of Dirac $4\times 4$ matrices suggests that the fundamental dimension of the internal (spin) space is $n=5$, instead of the conventional dimension $n=4$. Then extending the usual $4\times 4$ tetrads (vierbein), gravity is described in terms of the 5-bein (fünfbein or five legs). We discuss the properties of the spacetime geometry induced from this 5-leg Dirac spinor theory, where the spin connection contains $10\times 4=40$ elements instead of 24 elements in the tetrad formulation of the general relativity theory.

gr-qc↗

A new quantum hydrodynamic description of ferroelectricity in spiral magnets

The strong coupling between magnetism and ferroelectricity was found in rare earth manganites, where the electric polarization could be induced by special magnetic ordering. There is no theoretical model that would allow us to study the static and dynamic properties of electric polarization in strongly correlated magnetic dielectrics. In the presented research, we have taken the main step towards the construction of such a fundamental model, and made a direct connection between the microscopic Katsura-Nagaosa-Balatsky theory and Mostovoy's phenomenological model for magnetically induced polarization. A novel description of the ferroelectricity of spin origin is proposed within the framework of the many-particle quantum hydrodynamics method. It is applied to the study of cells of magnetic ions, where the electric dipole moment is proportional to the vector product of spins. Our approach is based on the many-particle Pauli equation, where the influence of an external magnetic field is considered. We define the electric dipole moment operator of the ion cell and introduce the macroscopic polarization as the quantum mechanical average of that operator. We formulate a model for the description of nonequilibrium polarization and derive a new polarization evolution equation. The polarization switching in ferroelectric magnets with the spiral spin-density-wave state is considered, and we demonstrate that the proposed model yields known results and can predict novel effects. The dynamic magnetoelectric effect can be investigated by employing this novel equation to study the evolution of polarization.

cond-mat.mtrl-sci↗

Hyperfluid model revisited

A new variational theory of a hyperfluid is constructed which is free of the supplementary condition issue and provides a consistent model of the classical matter source in the metric-affine gravity theory.

gr-qc↗

Nonmetricity and hypermomentum: on the possible violation of Lorentz invariance

We outline how the symmetry groups of spacetime are interpreted in a gauge-theoretic approach. Specifically, we focus on the hypermomentum concept and discuss the hyperfluid, that appropriately generalizes the perfect (Euler) fluid of general relativity to the case of continuous media with microstructure. We demonstrate that a possible violation of Lorentz invariance is most adequately understood by means of non-vanishing nonmetricity of a metric-affine geometry of spacetime.

gr-qc↗

Spin-Gravity Coupling in a Rotating Universe

The coupling of intrinsic spin with the nonlinear gravitomagnetic fields of Goedel-type spacetimes is studied. We work with Goedel-type universes in order to show that the main features of spin-gravity coupling are independent of causality problems of the Goedel universe. The connection between the spin-gravitomagnetic field coupling and Mathisson's spin-curvature force is demonstrated in the Goedel-type universe. That is, the gravitomagnetic Stern--Gerlach force due to the coupling of spin with the gravitomagnetic field reduces in the appropriate correspondence limit to the classical Mathisson spin-curvature force.

gr-qc↗

Spin as a probe of axion physics in general relativity

The dynamics of spin in external electromagnetic, gravitational, and axion fields is analysed in the framework of the gravitoelectromagnetism approach in Einstein's general relativity theory. We consistently extend the recent studies from the flat Minkowski geometry to the curved spacetime manifolds, contributing to the discussion of the possible new role of a precessing spin as an ``axion antenna'' that can be used to detect the hypothetical axion-like dark matter. The formalism developed helps to clarify the subtle influence of the gravitational/inertial and axion fields in the ultra-sensitive high-energy spin experiments with charged particles and neutrons at accelerators and storage rings devoted to testing fundamental physical symmetries, including attempts to establish the nature of dark matter in the Universe.

gr-qc↗

General relativity effects in precision spin experimental tests of fundamental symmetries

A search for the $P$- and $CP(T)$-violating electric dipole moments (EDM) of atoms, particles and nuclei with sensitivity up to $10^{-15}$ in units of magnetic dipole moments, allowed by all discrete symmetries, is one of the topical problems of modern physics. According to Sakharov, $CP$-violation is one of the three key criteria of baryogenesis in generally accepted paradigm of the Big Bang cosmology. All three criteria are supported by the Standard Model (SM), but it fails to describe the observed baryon asymmetry of the Universe. This is regarded a strong argument in favor of existence of $CP$-symmetry breaking mechanisms beyond minimal SM, which can lead to measurable EDMs of atoms, particles and nuclei. Direct searches for EDM of charged particles and nuclei are possible only in storage rings (COSY, NICA). After successful studies by the JEDI collaboration at the COSY synchrotron, at the forefront is a search for the proton EDM in an electrostatic storage ring with the proton spin frozen at the magic energy with projected sensitivity $d_p\sim 10^{-29}\,e\cdot$cm. Following a brief introduction to the $CP$-violation physics and the baryogenesis, the review presents a detailed discussion of significant contributions to the spin dynamics from the terrestrial gravity along with the new effects of Earth's rotation in ultrasensitive searches for the EDM of charged particles and neutrons. Quite remarkably, for the projected sensitivity to the proton EDM, these false EDM effects can by one to two orders of magnitude exceed the signal of the proton EDM, and become comparable to an EDM contribution in experiments with ultracold neutrons. We also discuss the role of a precessing spin as a detector of the axion-like dark matter, and consider applications of the quantum gravitational anomalies to the dense matter hydrodynamics and the spin phenomena in the non-central nuclear collisions.

hep-th↗

On parity-odd sector in metric-affine theories

We undertake the construction of quadratic parity-violating terms involving the curvature in the four-dimensional metric-affine gravity. We demonstrate that there are only 12 linearly independent scalars, plus an additional one that can be removed by using the Pontryagin invariant. Several convenient bases for this sector are provided in both components and differential form notation. We also particularize our general findings to some constrained geometries like Weyl-Cartan and metric-compatible connections.

gr-qc↗

Momentum of light in complex media

An important issue in phenomenological macroscopic electrodynamics of moving media is the definition of the energy and momentum of the electromagnetic field in matter. Rather surprisingly, this topic has demonstrated a remarkable longevity, and the problem of the electromagnetic energy and momentum in matter remained open, despite numerous theoretical and experimental investigations. We overview the definition of the momentum of light in matter and demonstrate that, for the correct understanding of the problem, one needs to carefully distinguish situations when the material medium is modeled either as a background for light or as a dynamical part of the total system. The status of Minkowski and Abraham energy-momentum tensors of the electromagnetic field is clarified for the two particular types of complex matter, the spinning fluid and the liquid crystal medium, and summarized for the case of general anisotropic moving material media with a linear constitutive law.

physics.optics↗

Poincaré gauge gravity primer

We give an introductory overview of the classical Poincaré gauge theory of gravity formulated on the spacetime manifold that carries the Riemann-Cartan geometry with nontrivial curvature and torsion. After discussing the basic mathematical structures at an elementary level in the framework of the standard tensor analysis, we formulate the general dynamical scheme of Poincaré gauge gravity for the class of Yang-Mills type models, and consider a selected number of physically interesting consequences of this theory.

gr-qc↗

Gravitomagnetic Helicity

Mass currents in astrophysics generate gravitomagnetic fields of enormous complexity. Gravitomagnetic helicity, in direct analogy with magnetic helicity, is a measure of entwining of the gravitomagnetic field lines. We discuss gravitomagnetic helicity within the gravitoelectromagnetic (GEM) framework of linearized general relativity. Furthermore, we employ the spacetime curvature approach to GEM in order to determine the gravitomagnetic helicity for static observers in Kerr spacetime.

gr-qc↗

Conservation laws in gauge gravity theory

We analyse the conservation laws in the gauge gravity theory which are derived for the general class of gravitational models with the action invariant under the local Poincare and the diffeomorphism group. The consistent Noether-Lagrange formalism is developed, revealing the important role of the auxiliary Goldstone and Stueckelberg fields, with the help of which we construct the composite gauge fields that have a clear geometrical and physical meaning.

gr-qc↗