Extragalactic Relativistic Jets and Nuclear Regions in Galaxies

Past years have brought an increasingly wider recognition of the ubiquity of relativistic outflows (jets) in galactic nuclei, which has turned jets into an effective tool for investigating the physics of nuclear regions in galaxies. A brief summary is given here of recent results from studies of jets and nuclear regions in several active galaxies with prominent outflows.Comment: 5 pages; contribution to ESO Astrophysical Symposia, "Relativistic Astrophysics and Cosmology", eds. B. Aschenbach, V. Burwitz, G. Hasinger, B. Leibundgut (Springer: Heidelberg 2006

Delay, memory, and messaging tradeoffs in distributed service systems

We consider the following distributed service model: jobs with unit mean, exponentially distributed, and independent processing times arrive as a Poisson process of rate $\lambda n$, with $0<\lambda<1$, and are immediately dispatched by a centralized dispatcher to one of $n$ First-In-First-Out queues associated with $n$ identical servers. The dispatcher is endowed with a finite memory, and with the ability to exchange messages with the servers. We propose and study a resource-constrained "pull-based" dispatching policy that involves two parameters: (i) the number of memory bits available at the dispatcher, and (ii) the average rate at which servers communicate with the dispatcher. We establish (using a fluid limit approach) that the asymptotic, as $n\to\infty$, expected queueing delay is zero when either (i) the number of memory bits grows logarithmically with $n$ and the message rate grows superlinearly with $n$, or (ii) the number of memory bits grows superlogarithmically with $n$ and the message rate is at least $\lambda n$. Furthermore, when the number of memory bits grows only logarithmically with $n$ and the message rate is proportional to $n$, we obtain a closed-form expression for the (now positive) asymptotic delay. Finally, we demonstrate an interesting phase transition in the resource-constrained regime where the asymptotic delay is non-zero. In particular, we show that for any given $\alpha>0$ (no matter how small), if our policy only uses a linear message rate $\alpha n$, the resulting asymptotic delay is upper bounded, uniformly over all $\lambda<1$; this is in sharp contrast to the delay obtained when no messages are used ($\alpha = 0$), which grows as $1/(1-\lambda)$ when $\lambda\uparrow 1$, or when the popular power-of-$d$-choices is used, in which the delay grows as $\log(1/(1-\lambda))$

The effect of confinement and defects on the thermal stability of skyrmions

The stability of magnetic skyrmions against thermal fluctuations and external perturbations is investigated within the framework of harmonic transition state theory for magnetic degrees of freedom. The influence of confined geometry and atomic scale non-magnetic defects on the skyrmion lifetime is estimated. It is shown that a skyrmion on a track has lower activation energy for annihilation and higher energy for nucleation if the size of the skyrmion is comparable with the width of the track. Two mechanisms of skyrmion annihilation are considered: inside the track and escape through the boundary. For both mechanisms, the dependence of activation energy on the track width is calculated. Non-magnetic defects are found to localize skyrmions in their neighborhood and strongly decrease the activation energy for creation and annihilation. This is in agreement with experimental measurements that have found nucleation of skyrmions in presence of spin-polarized current preferably occurring near structural defects

The Location of the Core in M81

We report on VLBI observations of M81*, the northwest-southeast oriented nuclear core-jet source of the spiral galaxy M81, at five different frequencies between 1.7 and 14.8 GHz. By phase referencing to supernova 1993J we can accurately locate the emission region of M81* in the galaxy's reference frame. Although the emission region's size decreases with increasing frequency while the brightness peak moves to the southwest, the emission region seems sharply bounded to the southwest at all frequencies. We argue that the core must be located between the brightness peak at our highest frequency (14.8 GHz) and the sharp bound to the southwest. This narrowly constrains the location of the core, or the purported black hole in the center of the galaxy, to be within a region of +/-0.2 mas or +/-800 AU (at a distance of ~4 Mpc). This range includes the core position that we determined earlier by finding the most stationary point in the brightness distribution of M81* at only a single frequency. This independent constraint therefore strongly confirms our earlier core position. Our observations also confirm that M81* is a core-jet source, with a one-sided jet that extends to the northeast from the core, on average curved somewhat to the east, with a radio spectrum that is flat or inverted near the core and steep at the distant end. The brightness peak is unambiguously identified with the variable jet rather than the core, which indicates limitations in determining the proper motion of nearby galaxies and in refining the extragalactic reference frame.Comment: LaTeX, 10 pages with 3 figures. Typos fixed and slight rewording for clarity from previous version. Accepted for publication in the Astrophysical Journa

Compact jets as probes for sub-parsec scale regions in AGN

Compact relativistic jets in active galactic nuclei offer an effective tool for investigating the physics of nuclear regions in galaxies. The emission properties, dynamics, and evolution of jets in AGN are closely connected to the characteristics of the central supermassive black hole, accretion disk and broad-line region in active galaxies. Recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution.Comment: AASLaTeX, 5 pages, 4 figures. Accepted in Astrophysics and Space Scienc

Determination of Structural Elements Size of the Finemet-type Amorphous Alloy

The sizes of structure elements were determined based on X-ray diffraction data in conjunction with simulation and scanning electron microscopy of the highest resolution for three states of the Fe72.5Cu1Nb2Mo1.5Si14B9alloy (amorphous, nanocrystalline, and recrystallized). It is shown that the sizes of the coherent scattering regions and crystallites for the nanocrystalline and recrystallized states have good agreement. It allows us to consider the cluster structure of solid "amorphous" materials as "ultra-nanocrystalline" consisting of crystallites with sizes of several interatomic distances. © 2021 Elsevier B.V.. All rights reserved.Russian Foundation for Basic Research, РФФИ: 20-38-90117The reported study was funded by RFBR, project number 20-38-90117. We appreciate the assistance from the program of support for the leading universities in the Russia Federation for improvement of their competitivenes

Neutrino spin rotation in dense matter and electromagnetic field

Exact solutions of the Dirac--Pauli equation for massive neutrino with anomalous magnetic moment interacting with dense matter and strong electromagnetic field are found. The complete system of neutrino wavefunctions, which show spin rotation properties are obtained and their possible applications are discussed.Comment: 11 pages, latex, misprints are correcte

The Effect of Copper and Manganese on the Amorphization Process in a Thin Fe–Si–Mg–O Film

The effect of copper and manganese on the amorphization process in the surface layer of a technical Fe-3% Si alloy during annealing in the α → γ transition temperature range was determined by x-ray phase analysis. The presence of 0.5 wt. % Cu and 0.3 wt. % Mn in the initial Fe-3% Si solid solution significantly enhances the amorphization process that occurs when heated in the temperature range 920… 960∘C as an alternative to the α → γ phase transformation. The effect of amplification of amorphization is both in obtaining a larger amount of material in the amorphous state, and in the appearance of two amorphous phases, differing in average interatomic distance. The composition of the amorphous phase is approximately described as Fe89Si6Mg4Mn0.5Cu0.5 in the presence of Cu and Mn atoms and Fe90Si6Mg4 in the case of their absence in the amorphous layer. &nbsp; &nbsp; Keywords: amorphization, non-ambient x-ray diffraction, Fe-3%Si, phase transition, thermal stability

The core shift effect in the blazar 3C 454.3

Opacity-driven shifts of the apparent VLBI core position with frequency (the "core shift" effect) probe physical conditions in the innermost parts of jets in active galactic nuclei. We present the first detailed investigation of this effect in the brightest gamma-ray blazar 3C454.3 using direct measurements from simultaneous 4.6-43 GHz VLBA observations, and a time lag analysis of 4.8-37 GHz lightcurves from the UMRAO, CrAO, and Metsahovi observations in 2007-2009. The results support the standard Konigl model of jet physics in the VLBI core region. The distance of the core from the jet origin r_c(nu), the core size W(nu), and the lightcurve time lag DT(nu) all depend on the observing frequency nu as r_c(nu)~W(nu)~ DT(nu)~nu^-1/k. The obtained range of k=0.6-0.8 is consistent with the synchrotron self-absorption being the dominating opacity mechanism in the jet. The similar frequency dependence of r_c(nu) and W(nu) suggests that the external pressure gradient does not dictate the jet geometry in the cm-band core region. Assuming equipartition, the magnetic field strength scales with distance r as B = 0.4(r/1pc)^-0.8 G. The total kinetic power of electron/positron jet is about 10^44 ergs/s.Comment: Accepted for publication in MNRAS; 10 pages, 6 figure

Solid state amorphization in a thin Fe-Si-Mg-O surface film triggered by the reduction of elements from oxides in the temperature range of the α-γ transformation

The study of the processes occurring in the surface layer of the MgO coated commercial alloy Fe-3%Si-0.5%Cu (grain oriented electrical steel) demonstrated that the amorphous phase in the form of a Fe-based solid solution is formed during continuous heating in the 95%N2 + 5%H2 atmosphere. For the purposes of this study, the following methods were used: non-ambient XRD at 20 –1060°C with heating and cooling at a rate of 0.5 dps, layer-by-layer chemical analysis performed by a glow discharge analyzer, scanning electron microscopy and energy dispersive X-ray spectroscopy. ThermoCalc software was used to calculate the potential phase equilibrium states. The amorphous phase was formed in the α → γ transformation temperature range, when the heating rates were altered in the surface layer of 1 µm initially consisted of a solid α-Fe-based solution with ~1– 2 wt.% Si with (MgFe)2 SiO4, (MgFe)O, SiO2 oxide inclusions. We suppose that (MgFe)2 SiO4 oxides are partly reduced by H2 to Mg2 Si molecular complexes, which become solid solutions in the temperature range of the metastability of the α-Fe crystal lattice with subsequent amorphization as an alternative to the α → γ transition. The amorphous state is obtained at 920 – 960°C and is retained both at subsequent heating (to 1060°C) and cooling (to 20°С), which is super-stable compared to the established metallic glasses. The composition of the amorphous phase can be described by the formula Fe89.5 Si6 Mg4 Cu0.5. © 2020, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Russian Foundation for Basic Research, RFBR: 20‑08‑00332Ministry of Education and Science of the Russian Federation, Minobrnauka: 11.1465.2014/K.Acknowledgements. This study was conducted using equipment provided by the Laboratory of Structural Analysis Techniques and Materials and Nanomaterials Properties of CKP Ural Federal University. The study was financially supported by Government Decree No. 211 of the Russian Federation, Contract No. 02. A03.21.0006 and within the framework of the state task issued by the Ministry of Education and Science of the Russian Federation, project No. 11.1465.2014/K. The reported study was funded by RFBR, project number 20‑08‑00332