arXiv subjects

Valentin Pomakov

Publications and source records attributed to Valentin Pomakov.

3 recordsLinked to original sources

arXiv2026

Bridging Superfluid and Nonminimally Coupled BEC Dark Matter through RAQUAL

Motivated by their common condensed-matter inspiration and their shared aim of reconciling MOND-like phenomenology on galactic scales with particle dark matter on larger scales, we investigate the relation between Superfluid Dark Matter (SFDM) and Bose--Einstein Condensate Dark Matter (BECDM). Since SFDM is formulated in the Newtonian regime whereas BECDM is fully relativistic, we first show that the MONDian formulation of SFDM arises as the Newtonian, low-acceleration limit of a Relativistic AQUAdratic Lagrangian (RAQUAL) theory in the Einstein frame. We then transform its covariant interaction sector to the Jordan frame and compare it with BECDM. The phonon--baryon interaction of SFDM maps onto the BECDM derivative coupling to the Einstein tensor, supplemented by a small non-minimal coupling to the Ricci scalar. The interaction sectors are therefore equivalent up to a linear perturbation of the Einstein--Hilbert term. Their kinetic sectors, however, remain inequivalent: the standard quadratic kinetic term of BECDM cannot be mapped onto the non-analytic kinetic term required by SFDM. The two models are consequently related but not dynamically equivalent. This mapping provides a covariant interpretation of the SFDM interaction and clarifies which theoretical properties can be transferred between the two frameworks.

gr-qc↗

arXiv2026

Analog regular black holes and black hole mimickers for surface-gravity waves in fluids

Recent advances in the observation of black-hole candidates have renewed interest in probing their near-horizon structure and in searching for departures from the standard singular solutions of general relativity. In this context, significant effort has been devoted to regular black holes and to horizonless black-hole mimickers, motivated primarily by quantum-gravitational effects. Depending on the value of the regularization parameter relative to the object mass, typical spherically symmetric solutions can describe either of these two scenarios. Regular black-hole configurations generically feature an outer and an inner horizon surrounding a maximally symmetric core; the inner horizon in turn triggers mass inflation and semiclassical instabilities. The horizonless branch of the same solutions, by contrast, supports stable inner light rings when sufficiently compact, yet is itself subject to instabilities associated with long-lived quasinormal modes. Here we investigate how to emulate these spacetimes in an analogue-gravity platform based on surface-gravity waves in a shallow-water basin, with the aim of reproducing these instabilities experimentally. We begin by identifying the flow profiles and boundary conditions required to replicate the relevant effective geometries. In particular, we show that the inner-core metrics can be simulated with a non-rotating central-drainage configuration, and we propose a graded-drainage profile to connect them to an asymptotically flat exterior region. We then assess the experimental feasibility of studying the instabilities mentioned above with current technology. Our conclusion is that, while the required setup is realizable in principle, alternative media, such as Bose-Einstein condensates, may offer a more practical route to faithfully capturing the targeted physical features.

gr-qc↗

arXiv2022

The redshift evolution of extragalactic magnetic fields

Faraday rotation studies of distant radio sources can constrain the evolution and the origin of cosmic magnetism. We use data from the LOFAR Two Metre Sky Survey: Data Release 2 (LoTSS DR2) to study the dependence of the Faraday rotation measure (RM) on redshift. By focusing on radio sources that are close in terms of their projection on the sky, but physically unrelated (random pairs), we measure the RM difference, $\Delta$RM, between the two sources. Thus, we isolate the extragalactic contribution to $\Delta$RM from other contributions. We present a statistical analysis of the resulting sample of random pairs and find a median absolute RM difference |$\Delta$RM| $ = (1.79 \pm 0.09)$ rad/m$^{2}$ , with |$\Delta$RM| uncorrelated both with respect to the redshift difference of the pair and the redshift of the nearer source, and a median excess of random pairs over physical pairs of $(1.65 \pm 0.10)$ rad/m$^{2}$. We seek to reproduce this result with Monte Carlo simulations assuming a non vanishing seed cosmological magnetic field and a redshift evolution of the comoving magnetic field strength that varies as $1/(1 + z)^{\gamma}$. We find the best fitting results $B_0 \equiv B_{\rm comoving}(z = 0) \lesssim (2.0 \pm 0.2)$ nG and $\gamma \lesssim 4.5 \pm 0.2$ that we conservatively quote as upper limits due to an unmodelled but non vanishing contribution of local environments to the RM difference. A comparison with cosmological simulations shows our results to be incompatible with primordial magnetogenesis scenarios with uniform seed fields of order nG.

astro-ph.CO↗