arXiv subjects

G. F. Akhtaryanova

Publications and source records attributed to G. F. Akhtaryanova.

4 recordsLinked to original sources

arXiv2026

Galactic microlensing by Lobo-Parsaei-Riazi phantom wormhole: Paczyński light curves and probabilistic features

Gravitational microlensing can provide a possible observational method for distinguishing between the signatures of massive and massless phantom wormholes. In this work, we consider Galactic microlensing by the bounded Lobo-Parsaei-Riazi phantom wormhole (LPR), assuming source stars located in the Galactic Bulge and in the Large Magellanic Cloud (LMC). We derive the weak-field deflection angle up to fourth post-Newtonian order and compute the Einstein radius, Einstein-radius crossing time, and idealized point-source Paczyński-type light curves. We also estimate the optical depth and event rate in a simplified model in which the wormhole lenses are assumed to be gravitationally bound to the Galaxy. The LPR parameter $γ$, which is related to the radial equation-of-state parameter by $ω= 1/ γ$, affects the ADM mass, the Einstein radius, and the microlensing timescale. In the massive phantom branch $-1 < γ< 0$, the leading deflection term is proportional to $1/r$, and the resulting point-source light curves are Paczyński-like. The massless comparison case $γ= 1$ is qualitatively different because the leading $1/r$ term vanishes and gutters may appear. The idealized observational predictions are compared with those for a Schwarzschild black hole.

gr-qc↗

arXiv2026

Stability regions of glued wormholes with massless Kim-Lee backreacted spacetimes as interior

Asymptotic zero Arnowitt-Deser-Misner (ADM) mass wormholes, such as the zero-mass traversable Ellis-Bronnikov wormhole, are of great interest for astrophysical applications such as in the galactic microlensing. However, when considered individually, they are unstable to small perturbations. On the other hand, there is a possibility that they can be stable as an interior partner of a traversable glued wormhole obtained by suitably gluing the interior to the observationally relevant massive exterior spacetimes across spherically symmetric thin shells. Although the exterior spacetime has non-zero ADM mass, massless interior partner remains massless sharing the stability of the glued wormhole. The dynamics of the thin-shell then demarcates the stability regions of the glued wormhole that we wish to study here by employing the novel concepts of thin-shell "mass" and of "external force" constraints discovered by Garcia, Lobo and Visser. We shall consider two classes, where the zero ADM mass interior are Kim-Lee wormholes glued to the exterior Schwarzschild vacuum and Reissner-Nordström spacetime respectively. It turns out that the stability regions in both cases are almost similar although the two interior Kim-Lee spacetimes are physically very different, one scalar charged and the other electrically charged. The conditions under which the stability of glued wormholes could be achieved are analyzed in detail.

gr-qc↗

arXiv2026

Galactic microlensing by backreacted massless wormholes

We study here a novel application of Kim \& Lee charged wormholes assuming them to be dark halo objects playing the role of lenses in the Galactic microlensing with source stars belonging to the Galactic Bulge and the Large Magellanic Cloud. First, we observe that both the backreacted scalar ($α$) and electrically ($Q$) charged wormholes have the same zero ADM mass as has the background Ellis-Bronnikov wormhole having a special equation of state parameter $γ=-1$. In particular, we argue that, for $α\neq 0$, the solution formally resembles, but can at best be sourcewise different from, that of the background wormhole. The charge ($Q\neq 0$) thus provides an extra degree of freedom that introduces a non-trivial redshift function $Φ$ to the background, alters its throat radius to $r_{th}$, yet keeps the wormhole massless. Second, we focus on this electrically charged case and calculate the light deflection angle up to 4$^{th}$ PPN order, analyze the effect of $Q$ on the lensing observables such as the image positions, magnification, centroid and time delay of images of the source stars. Third, we analyze the probabilistic features such as optical depth and event rate estimated on the basis of the hypothesis that the wormhole lens could be bound or unbound to our Galaxy. Finally, we report an intriguing qualitative prediction that, compared to the Schwarzschild black hole, the Paczyński light curves of the electrically charged wormhole are much dimmer that also show characteristic gutters at the times the source enters and exits the Einstein ring. \textit{The gutters gradually come together as $Q$ approaches the extreme limit $r_{th}/\sqrt{2}$, at which the Einstein radius $R_{E}$ vanishes so that the source crosses it instantly.} It is speculated that re-analyzing past data on Galactic microlensing may betray the presence of charged wormholes.

gr-qc↗

arXiv2026

Galactic microlensing by acoustic Schwarzschild black holes

This work explores the application of acoustic black holes as a novel class of lenses in Galactic microlensing, potentially representing dark matter halo objects. While sharing key features like an event horizon, their underlying fluid-dynamical description differs from the vacuum solutions of Einstein's equations, suggesting potentially distinct observational signatures. This work investigates these distinctions by calculating the galactic microlensing predictions for acoustic black holes and comparing them to the standard Schwarzschild case. Using the observed parameters of known black hole candidates (Cygnus X-1, A0620-00, GRO J1655-40) as illustrative lenses, we demonstrate that the acoustic black holes tuning parameter $ξ$ significantly alters key observables. Our results show that an increase in $ξ$ leads to a larger Einstein ring radius, a longer event duration, and a higher peak magnification in the microlensing Paczyński light curves. Furthermore, we find that the microlensing event rate is enhanced for acoustic black holes compared to their Schwarzschild counterparts, with the probability of detection growing with $ξ$. These findings establish galactic microlensing as a promising astrophysical channel for constraining analogue gravity metrics, with the primary effects being potentially detectable in the statistical analysis of current and future microlensing survey data.

gr-qc↗