E. L. Karapetyan | Searcharxiv

arXiv2026

Topological defects and scalar field modes in warped geometries

We develop a general framework for investigating the influence of topological defects on the local characteristics of a quantum scalar field in a warped geometry background. The Ricci tensor and curvature scalar are decomposed into contributions from the warp factor, the radial geometry and the angular defect structure. For an arbitrary curvature coupling parameter, the field equation is separated into independent radial, angular and warp-coordinate parts. A complete set of normalized mode functions is obtained for general values of the angular deficit parameters. The general formalism is applied to several specific cases, such as conformally flat warped spacetimes, generalized cosmic strings, global monopoles and anti-de Sitter (AdS)-type warped geometries. The Hadamard two-point function is then evaluated for a global monopole in AdS spacetime using the obtained mode functions.

hep-th↗

arXiv2025

Studies of stationary features in jets: 3C 279 quasar I. On-sky scattering and dynamics

A recent study on the dynamics of the quasi-stationary component (QSC) in the jet of BL~ Lacertae highlighted its significance in evaluating the physical properties of relativistic transverse waves in the parsec-scale jet. Motivated by this finding, we selected a different type of blazar, the flat-spectrum radio quasar (FSRQ) 3C~279, which hosts a QSC at an angular median distance of 0.35~mas from the radio core, as revealed by 27 years of VLBA monitoring data at 15~GHz. We investigate the positional scatter and dynamics of a QSC in the 3C~279 jet, aiming to detect the presence of a relativistic transverse wave and estimate its characteristics. We employ an analytical statistical method to estimate the mean intrinsic speed of the QSC, while moving average and refinement methods are used to smooth its trajectory. Analysis of the QSC position scatter shows that the jet axis change its direction by about $21^{\circ}$ over 27 years and jet mean intrinsic full opening angle is $\approx 0.30^{\circ} \pm 0.03^{\circ}$. The apparent displacement vectors of the QSC exhibit strong asymmetry and anisotropy along the jet direction, indicating pronounced anisotropic displacements of the core along the jet axis. We estimated the mean intrinsic speed of the QSC to be superluminal, $\overline{β_{\rm s}} \approx 10$ in units of the speed of light, which, within the framework of the seagull-on-wave model, is interpreted as evidence for a relativistic transverse wave propagating through the QSC. Analysis of the reversing trajectory of the QSC enables the classification and characterisation of reversal patterns, which, in turn, allows the determination of key transverse wave parameters such as frequency, amplitude, inclination angle, and magnetic energy of the wave (abbrev.).

astro-ph.GA↗