arXiv subjects

Alexander Tsirulev

Publications and source records attributed to Alexander Tsirulev.

4 recordsLinked to original sources

arXiv2026

Charged topological geons with a self-gravitating scalar field

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 manifold $M$ is conventionally obtained from a spherically symmetric spatial slice of a wormhole spacetime as the quotient manifold by the isometric action of the group $\mathbb{Z}_2$. We study the general properties of static, spherically symmetric, charged topological geons supported by a selfgravitating, minimally coupled scalar field with negative kinetic energy and an arbitrary selfinteraction potential. In the most general case, it turns out that the gravitational mass of such a geon is completely determined by its electric charge and size (for a given scalar field), that is, the size of the corresponding wormhole throat. We discuss the properties of the charged Ellis-Bronnikov-Sorkin geon and argue that it can be considered as a possible classical model of elementary particles beyond the Standard Model, in particular, as dark matter particles.

gr-qc↗

arXiv2025

Computation of operator exponentials using the Dunford-Cauchy integral

We consider an n-qubit quantum system with a Hamiltonian, defined by an expansion in the Pauli basis, and propose a new algorithm for classical computing the exponential of the Hamiltonian. The algorithm is based on the representation of the exponential by the Dunford-Cauchy integral, followed by an efficient computation of the resolvent, and is suitable for Hamiltonians that are sparse in the Pauli basis. The practical efficiency of the algorithm is demonstrated by two illustrative examples.

quant-ph↗

arXiv2024

Tidal Disruption of Stars by Supermassive Black Holes and Naked Singularities with Scalar Hair

In this paper we study tidal forces near strongly gravitating objects at the centers of galaxies. In our approach, dark matter surrounding the centers of galaxies is modeled by a nonlinear scalar field. We focus on static, asymptotically flat, spherically symmetric black holes and naked singularities supported by a real self-gravitating scalar field minimally coupled to gravity. We consider the influence of dark matter on the tidal forces caused by the central objects and some features of the motion of matter near these configurations. It turns out, first, that the event horizon radius of a scalar field black hole can be arbitrarily small as well as the radius of the innermost stable circular orbit, and tidal forces near this orbit can be very large. Second, we show that if strongly gravitating objects in the centers of galaxies are naked singularities, then bright flares (tidal disruption events) in the nuclei of galaxies can be explained in different way. In the vicinity of a scalar field naked singularity, baryonic matter is concentrated in the gravitational potential well forming a "gray shell" consisting of cold compressed matter. In this case, the flares are caused by the collisions of stars with this shell.

gr-qc↗

arXiv2020

Null and Timelike Geodesics Near the Throats of Phantom Scalar Field Wormholes

We study geodesic motion near the throats of asymptotically flat, static, spherically~symmetric traversable wormholes supported by a self-gravitating minimally coupled phantom scalar field with an arbitrary self-interaction potential. We assume that any such wormhole possesses the reflection symmetry with respect to the throat, and consider only its observable "right~half". It turns out that the main features of bound orbits and photon trajectories close to the throats of such wormholes are very different from those near the horizons of black holes. We~distinguish between wormholes of two types, the first and second ones, depending on whether the redshift metric function has a minimum or maximum at the throat. First, it turns out that orbits located near the centre of a wormhole of any type exhibit retrograde precession, that is, the angle of pericentre precession is negative. Second, in the case of high accretion activity, wormholes of the first type have the innermost stable circular orbit at the throat while those of the second type have the resting-state stable circular orbit in which test particles are at rest at all times. In our study, we have in mind the possibility that the strongly gravitating objects in the centres of galaxies are wormholes, which can be regarded as an alternative to black holes, and the scalar field can be regarded as a realistic model of dark matter surrounding galactic centres. In this connection, we~discuss qualitatively some observational aspects of results obtained in this article.

gr-qc↗