Quantum dynamics in canonical and micro-canonical ensembles. Part I. Anderson localization of electrons

The new numerical approach for consideration of quantum dynamics and calculations of the average values of quantum operators and time correlation functions in the Wigner representation of quantum statistical mechanics has been developed. The time correlation functions have been presented in the form of the integral of the Weyl's symbol of considered operators and the Fourier transform of the product of matrix elements of the dynamic propagators. For the last function the integral Wigner- Liouville's type equation has been derived. The numerical procedure for solving this equation combining both molecular dynamics and Monte Carlo methods has been developed. For electrons in disordered systems of scatterers the numerical results have been obtained for series of the average values of the quantum operators including position and momentum dispersions, average energy, energy distribution function as well as for the frequency dependencies of tensor of electron conductivity and permittivity according to quantum Kubo formula. Zero or very small value of static conductivity have been considered as the manifestation of Anderson localization of electrons in 1D case. Independent evidence of Anderson localization comes from the behaviour of the calculated time dependence of position dispersion.Comment: 8 pages, 10 figure

МОДЕЛЬ ИССЛЕДОВАНИЯ УСТОЙЧИВОСТИ СИСТЕМЫ «РУЛЬ - ПРИВОД» МАНЕВРЕННОГО БЕСПИЛОТНОГО ЛЕТАТЕЛЬНОГО АППАРАТА

One of the important problems of the designing of maneuverable unmanned aerial vehicles (UAV) is to ensure aeroelastic stability with automatic control system (ACS). One of the possible types of aeroelastic instability of UAV with ACS is loss of stability in the «rudder-actuator» system. To study the stability of the «rudder-actuator» system of the maneuverable UAV the linearized model was developed. The system consists of hard rudder, performing flexural and torsional oscillations, and the fixedly mounted control surface electric actuator. The «rudder-actuator» system has three degrees of freedom: bending of the rudder, the rotation of the rudder and the angular displacement of the actuator shaft. The rudder, performing bending-torsion oscillations in aerodynamic flow, in fact, is the loading for the actuator. Investigation of the «rudder-actuator» system stability is carried out by frequency method with the use of frequency characteristics of the open-loop system. An example of stability analysis of the «rudder-actuator» system is given.Рассматривается модель исследования устойчивости системы «руль-привод», разработанная в интересах решения задач совместного проектирования конструкции планера и системы автоматического управления маневренного беспилотного летательного аппарата с учетом требований аэроупругой устойчивости. Исследование устойчивости проводится частотным методом с использованием частотных характеристик разомкнутой системы «руль-привод». Приводится пример исследования устойчивости системы «руль-привод»

Landau Level Crossings and Extended-State Mapping in Magnetic Two-dimensional Electron Gases

We present longitudinal and Hall magneto-resistance measurements of a ``magnetic'' two-dimensional electron gas (2DEG) formed in modulation-doped Zn$_{1-x-y}$Cd$_{x}$Mn$_{y}$Se quantum wells. The electron spin splitting is temperature and magnetic field dependent, resulting in striking features as Landau levels of opposite spin cross near the Fermi level. Magnetization measurements on the same sample probe the total density of states and Fermi energy, allowing us to fit the transport data using a model involving extended states centered at each Landau level and two-channel conduction for spin-up and spin-down electrons. A mapping of the extended states over the whole quantum Hall effect regime shows no floating of extended states as Landau levels cross near the Fermi level.Comment: 10 pages, 4 figures, submitted to Phys. Rev.

НЕЛИНЕЙНАЯ МОДЕЛЬ ИССЛЕДОВАНИЯ УСТОЙЧИВОСТИ СИСТЕМЫ «РУЛЬ – ПРИВОД» МАНЕВРЕННОГО БЕСПИЛОТНОГО ЛЕТАТЕЛЬНОГО АППАРАТА

One of the important problems of the designing of maneuverable unmanned aerial vehicles (UAV) is to ensure aeroelastic stability with automatic control system (ACS). One of the possible types of aeroelastic instability of UAV with ACS is loss of stability in the system "surface control – actuator".  A nonlinear model for the study of the stability of the system "surface control – actuator" is designed for solving problems of joint design of airframe and ACS with the requirements of aeroelasticity. The electric actuator is currently the most widely used on highly maneuverable UAV. The wide bandwidth and the availability of frequency characteristic lifts are typical for the modern electric actuator. This exacerbates the problem of providing aeroelastic stability of the UAV with ACS, including the problem of ensuring the stability of the system "surface control – actuator". In proposed model the surface control, performing bending-torsion oscillations in aerodynamic flow, in fact, is the loading for the actuator. Experimental frequency characteristics of the isolated actuator, obtained for different levels of the control signal, are used for the mathematical description of the actuator, then, as dynamic hinge moment, which is determined by aeroelastic vibrations of the surface control in the air flow, is calculated. Investigation of the stability of the system "surface control – actuator" is carried out by frequency method using frequency characteristics of the open-loop system. The undeniable advantage of the proposed model is the simplicity of obtaining the transfer functions of the isolated actuator. The experiment by its definition is a standard method of determining frequency characteristics of the actuator in contrast to time-consuming experiments for determining the dynamic stiffness of the actuator (with the surface control) or the transfer function of the actuator using electromechanical simulation of aeroelastic loading of the surface control, that also used in research stability problems of the system "surface control – actuator".Одной из актуальных задач проектирования современных высокоманевренных беспилотных летательных аппаратов (БЛА) является обеспечение аэроупругой устойчивости с системой автоматического управления (САУ). Одним из возможных видов аэроупругой неустойчивости БЛА с САУ является потеря устойчивости в системе «руль – привод». В интересах решения задач совместного проектирования конструкции БЛА и САУ с учетом требований аэроупругости разработана нелинейная модель исследования устойчивости системы «руль – привод». В качестве привода рассмотрен электропривод, который в настоящее время наиболее широко используется на высокоманевренных БЛА. Для современного электропривода характерны: широкая полоса пропускания и наличие подъемов частотной характеристики. Это обостряет проблемы обеспечения аэроупругой устойчивости БЛА с САУ, в том числе проблему обеспечения устойчивости системы «руль – привод».  В предлагаемой модели руль, совершающий изгибные и крутильные колебания в аэродинамическом потоке, является по сути нагружением привода. Для математического описания привода используются экспериментальные частотные характеристики изолированного рулевого привода, полученные для различных уровней управляющего сигнала, а динамический шарнирный момент, определяемый аэроупругими колебаниями руля в потоке, находится расчетным способом. Исследование устойчивости проводится частотным методом с использованием частотных характеристик разомкнутой системы «руль – привод». Неоспоримым преимуществом предлагаемой модели является простота получения передаточной функции изолированного рулевого привода по управляющему сигналу. Эксперимент по ее определению представляет собой стандартный способ определения частотных характеристик рулевого привода в отличие от трудоемких экспериментов по определению динамической жесткости рулевого привода или передаточной функции привода при электромеханическом моделировании аэроупругого нагружения руля, также используемых в задачах исследования устойчивости системы «руль – привод»

Should the teaching of biological evolution include the origin of life?

The development of mainstream research on the origin of life as an outcome of Darwinian evolution is discussed. It is argued that prebiotic evolution and the origin of life should not be excluded from the syllabus and should be part of classes on biological evolution, and that the transition from non-living to living matter is best understood when seen as part of evolutionary biology. The wide acceptance of evolutionary approaches to the study of the emergence of life in European and Latin American countries is discussed

Optical Identification and Spectroscopic Redshift Measurements of 216 Galaxy Clusters from the SRG/eROSITA All-Sky Survey

We present the results of the optical identification and spectroscopic redshift measurements of 216 galaxy clusters detected in the SRG/eROSITA all-sky X-ray survey. The spectroscopic observations were performed in 2020-2023 with the 6-m BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences, the 2.5-m telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Moscow State University, the 1.6-m AZT-33IK telescope at the Sayan Solar Observatory of the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences, and the 1.5-m Russian-Turkish telescope (RTT-150) at the T\"{U}B\.{I}TAK Observatory. For all of the galaxy clusters presented here the spectroscopic redshift measurements have been obtained for the first time. Of these, 139 galaxy clusters have been detected for the first time in the SRG/eROSITA survey and 22 galaxy clusters are at redshifts $z_{spec} \gtrsim 0.7$, including three at $z_{spec} \gtrsim 1$. Deep direct images with the rizJK filters have also been obtained for four distant galaxy clusters at $z_{spec} > 0.7$. For these observations the most massive clusters are selected. Therefore, most of the galaxy clusters presented here most likely will be included in the cosmological samples of galaxy clusters from the SRG/eROSITA survey

Behavioral metabolution: the adaptive and evolutionary potential of metabolism-based chemotaxis

We use a minimal model of metabolism-based chemotaxis to show how a coupling between metabolism and behavior can affect evolutionary dynamics in a process we refer to as behavioral metabolution. This mutual influence can function as an in-the-moment, intrinsic evaluation of the adaptive value of a novel situation, such as an encounter with a compound that activates new metabolic pathways. Our model demonstrates how changes to metabolic pathways can lead to improvement of behavioral strategies, and conversely, how behavior can contribute to the exploration and fixation of new metabolic pathways. These examples indicate the potentially important role that the interplay between behavior and metabolism could have played in shaping adaptive evolution in early life and protolife. We argue that the processes illustrated by these models can be interpreted as an unorthodox instantiation of the principles of evolution by random variation and selective retention. We then discuss how the interaction between metabolism and behavior can facilitate evolution through (i) increasing exposure to environmental variation, (ii) making more likely the fixation of some beneficial metabolic pathways, (iii) providing a mechanism for in-the-moment adaptation to changes in the environment and to changes in the organization of the organism itself, and (iv) generating conditions that are conducive to speciatio

Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631

We present an observational study of the luminous red nova (LRN) AT\,2021biy in the nearby galaxy NGC\,4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from $\sim 231$\,days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT\,2021biy shows a short-duration blue peak, with a bolometric luminosity of $\sim 1.6 \times 10^{41}$\,erg\,s$^{-1}$, followed by the longest plateau among LRNe to date, with a duration of 210\,days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT\,2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum ($T_{\mathrm{BB}} \approx 2050$ K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT\,2021biy has local dust properties similar to those of V838\,Mon in the Milky Way Galaxy. Inspection of archival {\it Hubble Space Telescope} data taken on 2003 August 3 reveals a $\sim 20$\,\msun\ progenitor candidate with log\,$(L/{\rm L}_{\odot}) = 5.0$\,dex and $T_{\rm{eff}} = 5900$\,K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17--24\,\msun\ primary component.Comment: 21 pages, 14 figures. Accepted by Astronomy and Astrophysic