Search

We search for reflection-dominated Compton-thick active galactic nuclei (CT AGN) candidates in the Lockman Hole region using the data of SRG/eROSITA Lockman Hole survey. We selected sources with anomalously hard photon indices in the $0.3 - 8.0$ keV band, untypical for type I AGN. In particular, we required that the upper end of the $90\%$ error interval did not exceed a fiducial boundary of $\Gamma=1.3$. We found 291 sources which constitute a rare subpopulation among extragalactic X-ray sources detected by eROSITA in the Lockman Hole field, $\approx 5\%$. These sources constitute the eROSITA sample of CT AGN candidates in the Lockman Hole field. We further divide the sources into three categories depending on the availability of reliable redshift and statistically significant detection of intrinsic absorption. We present two catalogues: the bright sample (37 sources) and the faint one (254). We estimate the fraction and sky density of reflection-dominated CT AGN candidates. We show examples of individual spectra and use stacking analysis to search for possible redshift evolution of their properties with redshift. We analyse combined eROSITA spectra of bright sources of different categories with a physically motivated spectral model UXCLUMPY and find them fully consistent with the fits to the about $\sim 1$ Msec XMM-Newton data for one of our reflection-dominated CT candidates, Type 2 galaxy $\text{SRGe J105348.6+573032}$. The catalogues of CT AGN candidates could be a good starting point for planning future studies and follow-ups at all wavelengths., Comment: Accepted for publication in MNRAS

We present a new description of the 7.7~$\mu$m region towards the high-mass star-forming region IRAS 23385+6053 taken from open James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer (JWST MIRI/MRS) data. This area is commonly attributed to the $\nu_4$ deformation mode of methane ice. For the first time gaseous and solid methane were analyzed simultaneously in IRAS 23385+6053. The band at 7.58--7.8 $\mu$m (1320--1280 cm$^{-1}$) is interpreted as a wide solid absorption methane feature overlapped by the sharp features of the methane emission. We report the detection of gaseous methane and estimate its emitting area radius~$R$, temperature~$T$ and column density~$N$ as $R=2940$~au, $T=103^{+13}_{-11}$~K, and $N=0.78_{+6.18}^{-0.64}\times10^{17}$~cm$^{-2}$, correspondingly. The ice content was analyzed with the laboratory spectra dataset of methane in different molecular environments obtained on the Ice Spectroscopy Experimental Aggregate (ISEAge). We were able to describe the wide feature of solid methane with the following laboratory spectra: CH$_4$~:~CO$_2$~=~1~:~5 (at $27.4^{+6.0}_{-10.8}$~K) and CH$_4$~:~H$_2$O~=~1~:~10 (at $8.4^{+16.4}_{-1.7}$~K) deposited at 6.7~K and warmed up at a rate of 0.5 K per minute. The derived column densities are $N_{\text{CH}_4}$(CO$_2$)~=~$2.97^{+0.37}_{-0.57}\times10^{17}$~cm$^{-2}$ and $N_{\text{CH}_4}$(H$_2$O)~=~$1.02^{+0.46}_{-0.27}\times10^{17}$~cm$^{-2}$. According to the best fit solid methane is mostly surrounded by CO$_2$ rather than H$_2$O. The residuals analysis reveals the unassigned region at 1283--1297~cm$^{-1}$ (7.71--7.79~$\mu$m) which is tentatively assigned to nitrous oxide (N$_2$O) in various environments., Comment: 12 pages, 6 figures, 1 table, accepted to ApJL

Objective: The objective of this study is to develop and evaluate a systematic approach to optimize Deep Brain Stimulation (DBS) parameters, addressing the challenge of identifying patient-specific settings and optimal stimulation targets for various neurological and mental disorders. Methods: TuneS, a novel pipeline to predict clinically optimal DBS contact configurations based on predefined targets and constraints, is introduced. The method relies upon patient-specific models of stimulation spread and extends optimization beyond traditional neural structures to include automated, model-based targeting of streamlines. Results: Initial findings demonstrate that STN motor streamlines consistently receive a significant portion of the allocated stimulation volume, suggesting that a consistent portion of the stimulation should ideally focus on the STN motor streamlines. At the example of a small cohort of Parkinson's disease patients, the value of model-based contact predictions for assessing stimulation targets while observing constraints is demonstrated. Conclusion: TuneS shows promise as a research tool, enabling systematic assessment of DBS target effectiveness and facilitating constraint-aware optimization of stimulation parameters. Significance: The presented pipeline offers a pathway to improve patient-specific DBS therapies and contributes to the broader understanding of effective DBS targeting strategies., Comment: 8 pages, 9 figures, submitted to IEEE Transactions on Biomedical Engineering

The Kuramoto model (KM) of $n$ coupled phase-oscillators is analyzed in this work. The KM on a Cayley graph possesses a family of steady state solutions called twisted states. Topologically distinct twisted states are distinguished by the winding number $q\in\mathbb{Z}$. These states are known to be stable for small enough $q$. In the presence of small noise, the KM exhibits metastable transitions between $q$-twisted states: A typical trajectory remains in the basin of attraction of a given $q$-twisted state for an exponentially long time, but eventually transitions to the vicinity of another such state. In the course of this transition, it passes in close proximity of a saddle of Morse index $1$, called a relevant saddle. In this work, we provide an exhaustive analysis of metastable transitions in the stochastic KM with nearest-neighbor coupling. We start by analyzing the equilibria and their stability. First, we identify all equilibria in this model. Using the discrete Fourier transform and eigenvalue estimates for rank-1 perturbations of symmetric matrices, we classify the equilibria by their Morse indices. In particular, we identify all stable equilibria and all relevant saddles involved in the metastable transitions. Further, we use Freidlin-Wentzell theory and the potential-theoretic approach to metastability to establish the metastable hierarchy and sharp estimates of Eyring-Kramers type for the transition times. The former determines the precise order, in which the metastable transitions occur, while the latter characterizes the times between successive transitions. The theoretical estimates are complemented by numerical simulations and a careful numerical verification of the transition times. Finally, we discuss the implications of this work for the KM with other coupling types including nonlocal coupling and the continuum limit as $n$ tends to infinity., Comment: 37 pages, 15 figures

The interplay between superconductivity and charge order is a central focus in condensed matter research, with kagome lattice systems offering unique insights. The kagome superconductor LaRu$_{3}$Si$_{2}$ ($T_{\rm c}$ ${\simeq}$ 6.5 K) exhibits a hierarchy of charge order transitions: primary ($T_{\rm co,I}$ ${\simeq}$ 400 K), secondary ($T_{\rm co,II}$ ${\simeq}$ 80 K), and an additional transition at ($T^{*}$ $\simeq$ 35 K). The transitions at $T_{\rm co,II}$ and $T^{*}$ are linked to electronic and magnetic responses as revealed by muon-spin rotation and magnetotransport experiments. However, the connection between superconductivity, charge order, and electronic responses has remained elusive. By employing magnetotransport and X-ray diffraction techniques under pressures of up to 40 GPa, we observe that $T_{\rm c}$ rises to 9 K at 2 GPa, remains nearly constant up to 12 GPa, and then decreases to 2 K at 40 GPa, resulting in a dome-shaped phase diagram. The resistivity anomaly at $T^{*}$ and magnetoresistance also exhibit a similar dome-shaped pressure dependence. Furthermore, we find that charge order transitions from long-range to short-range above 12 GPa, correlating with the suppression of $T_{\rm c}$, suggesting superconductivity is closely tied to the charge-ordered state. Specifically, $T_{\rm c}$ peaks when charge order and the normal-state electronic responses are optimized. In contrast to systems like the cuprates, transition metal dichalcogenides, and other kagome materials, where superconductivity typically competes with charge order, LaRu$_{3}$Si$_{2}$ displays a pronounced interdependence between these two phenomena. This distinctive behavior sheds new light on the connection between superconductivity and charge order, offering avenues for theoretical advancements in understanding superconductivity.

The yields of the inverse beta decay events produced by antineutrinos from a certain nuclear reactor fuel component are used by many experiments to check various model predictions. Yet measurements of the absolute yields feature significant uncertainties coming, mainly, from the understanding of the antineutrino detection efficiency. This work presents a simple novel approach to directly determine the $^{235}$U to $^{239}$Pu inverse beta decay yield ratio using the fuel evolution analysis. This ratio can be used for a sensitive test of reactor models, while the proposed method, results in smaller systematic uncertainties., Comment: 5 pages, 2 figures

Electron antineutrinos are emitted in the decay chains of the fission products inside a reactor core and could be used for remote monitoring of nuclear reactors. The DANSS detector is placed under the core of the 3.1 GW power reactor at the Kalinin Nuclear Power Plant (KNPP) and collects up to 5000 antineutrino events per day. DANSS measured changes of the reactor power by antineutrino counting rates over 7 years with 1.0% accuracy in one week periods. The systematic uncertainty of this measurement is less than 0.8%. It is comparable to the accuracy of conventional methods of the reactor power measurements while it is based on completely different approach. For the first time the 239Pu and 235U fission fractions were reconstructed using antineutrino inverse beta-decay spectrum which is a completely new technique. This method was applied to the data from three reactor fuel campaigns (approximately 1.5 year each). The reconstructed fission fractions in about one week measurements and the fission fractions provided by KNPP coincide within about 3% accuracy. This provides confidence in both completely different approaches of the fission fraction determination.

Deep Brain Stimulation (DBS) is a therapy widely used for treating the symptoms of neurological disorders. Electrical pulses are chronically delivered in DBS to a disease-specific brain target via a surgically implanted electrode. The stimulating contact configuration, stimulation polarity, as well as amplitude, frequency, and pulse width of the DBS pulse sequence are utilized to optimize the therapeutic effect. In this paper, the utility of therapy individualization by means of patient-specific mathematical modeling is investigated with respect to a specific case of a patient diagnosed with Essential Tremor (ET). Two computational models are compared in their ability to elucidate the impact of DBS stimulation on the dentato-rubrothalamic tract: (i) a conventional model of Volume of Tissue Activated (VTA) and (ii) a well-established neural fiber activation modeling framework known as OSS-DBS. The simulation results are compared with tremor measured in the patient under different DBS settings using a smartphone application. The findings of the study highlight that temporally static VTA models do not adequately describe the differences in the outcomes of bipolar stimulation settings with switched polarity, whereas neural fiber activation models hold potential in this regard. However, it is noted that neither of the investigated models fully accounts for the measured symptom pattern, particularly regarding a bilateral effect produced by unilateral stimulation., Comment: 7 pages, 5 figures, 5 tables

Static manifolds with boundary were recently introduced to mathematics. This kind of manifolds appears naturally in the prescribed scalar curvature problem on manifolds with boundary, when the mean curvature of the boundary is also prescribed. They are also interesting from the point of view of General Relativity. For example, the (time-slice of the) photon sphere on the Riemannian Schwarzschild manifold splits it into static manifolds with boundary. In this paper we prove a number of theorems, which relate the topology and geometry of a given static manifold with boundary to some properties of the zero-level set of its potential (such as connectedness and closedness). Also, we characterize the round ball in the Euclidean 3-space with standard potential as the only scalar-flat static manifold with mean-convex boundary, whose zero-level set of the potential has Morse index one. This result follows from a general isoperimetric inequality for 3-dimensional static manifolds with boundary, whose zero-level set of the potential has Morse index one. Finally, we prove some uniqueness theorem for the domains bounded by the photon sphere on the Riemannian Schwarzschild manifold., Comment: 28 pages; Theorem 1.10 is slightly improved; some typos are corrected

The best available line list of OH [Brooke et al. (2016)] contains the high-quality line frequencies, yet the line intensities need refinement because the model function used to interpolate the RKR potential and to extrapolate it into the repulsion region was not analytic [Medvedev et al. Mol. Phys. (2024)], and also because the coupling between the ground $X^2\Pi$ and first excited $A^2\Sigma^+$ electronic states was treated by the perturbation theory. In this paper, we performed ab initio calculations of all necessary molecular functions at $r=0.4$-8.0 bohr, and then we construct fully analytic model functions entering the Hamiltonian. The model functions were fitted to both the \ai\ data and the available experimental data on the line positions and energy levels, the relative line intensities, and the transition dipole moments derived from the measured permanent dipoles. The system of three coupled Schr\"odinger equations for two multiplet components of the $X$ state plus the $A$ state was solved to calculate the energy levels and the line intensities. The new set of the \EinA\ permits to decrease the scatter of the logarithmic populations of the ro-vibrational levels derived from the observed radiation fluxes [Noll et al. (2020)], to achieve better agreement with the measured relative intensities, and to obtain significant differences in the intensities of the $\Lambda$ doublets for large $v$ and $J$ as observed by Noll et al. The $X$-$A$ coupling fully modifies the Q-line intensities at high $J$ by removing the well-known $J^{-2}$ dependence. A new line list is constructed where the transition frequencies are from Brooke \etal\ and the \EinA\ are from the present study. However, not all the problems with the intensities were resolved, presumably due to the neglect of the interaction with the $^4\Sigma^-,^2\Sigma^-$ and $^4\Pi$ repulsive electronic terms.

The model explaining the spectral "zebra" pattern of the high-frequency interpulse (HFIP) of the Crab pulsar radio emission is proposed. The observed emission bands are diffraction fringes in the spectral domain. The pulsar's own plasma-filled magnetosphere plays a role of a frequency-dependent "diffraction screen". The observed features such as the proportional band spacing, high polarization, constant position angle, and others are explained. The model allows one to perform "tomography" of the pulsar magnetosphere. Indeed, we have obtained the plasma density profile directly from observations, without assuming a particular magnetosphere. Our model is testable and several predictions are made. The two "high-frequency components" observed at the same frequencies as the HFIP are proposed to be related to HFIP., Comment: 7 pages, published in PRL, matches published version

We report the discovery of a short, large amplitude X-ray flare from AT2019vcb (aka Tormund), a tidal disruption event at $z=0.088$. The discovery is based on the data from the SRG/eROSITA X-ray telescope which happened to observe the source seven months after the onset of the optical TDE. eROSITA observation occurred 13 days after a soft flare was detected in the XMM-Newton data by Quintin et al. 2023. Both events bear similar characteristics in terms of timing and spectral properties. eROSITA spectrum is described as an accretion disk with a characteristic temperature of $\sim180$ eV and luminosity $\sim8\times10^{43}$ erg/s. The eROSITA flare lasted less than 12 hours and had an amplitude $\ge70$ with respect to the quiescent level, no flares were detected in later eROSITA observations (6-18 months later). The XMM-Newton and eROSITA flares provide strong evidence that the TDE AT2019vcb is a bona fide QPE source. Our work further strengthens the direct connection between TDEs and QPE following similar recent results in a TDE AT2019qiz by Nicholl et al. 2024., Comment: submitted to MNRAS, comments welcome

RhBi$_2$ is a polymorphic system that exhibits two distinct phases. RhBi$_2$ in the triclinic phase has been identified as a weak topological insulator with a van Hove singularity point close to the Fermi energy. Thus, triclinic RhBi$_2$ is expected to exhibit exotic quantum properties under strain or pressure. In this study, we report on the emergence of superconductivity in the monoclinic RhBi$_2$ under external pressures. The electrical resistivity behavior of the monoclinic RhBi$_2$ single crystal is studied at a wide range of applied external pressures up to 40 GPa. We observe a pressure-induced superconductivity with a dome-shaped dependence of the critical temperature on pressure at pressures above 10 GPa. A maximum critical temperature ($T_\mathrm{c}$) value of $T_\mathrm{c}$ = 5.1 K is reached at the pressure of 16.1 GPa. Furthermore, we performed detailed ab initio calculations to understand the electronic band structures of monoclinic RhBi$_2$ under varying pressures. The combination of topology and pressure-induced superconductivity in the RhBi$_2$ polymorphic system may provide us with a new promising material platform to investigate topological superconductivity., Comment: 6 pages, 5 figure

We report superconductivity in the ternary compound IrBi$_{0.8}$Te$_{1.2}$ with critical temperature 1.7 K. The replacement of Bi by Te leads to the metallic conductivity in contrast to the semiconducting parent compound IrBiTe. The superconductivity can be further enhanced by application of external pressure. $T_c$ demonstrates dome-shaped dependence on pressure with a maximum value of 2.6 K at 26.5 GPa. Pressure effects on electronic properties and lattice dynamic of IrBi$_{0.8}$Te$_{1.2}$ were studied by pressure dependent electrical resistivity, Hall effect and Raman spectroscopy measurements., Comment: 15 pages, 4 figures

We consider the overfitting behavior of minimum norm interpolating solutions of Gaussian kernel ridge regression (i.e. kernel ridgeless regression), when the bandwidth or input dimension varies with the sample size. For fixed dimensions, we show that even with varying or tuned bandwidth, the ridgeless solution is never consistent and, at least with large enough noise, always worse than the null predictor. For increasing dimension, we give a generic characterization of the overfitting behavior for any scaling of the dimension with sample size. We use this to provide the first example of benign overfitting using the Gaussian kernel with sub-polynomial scaling dimension. All our results are under the Gaussian universality ansatz and the (non-rigorous) risk predictions in terms of the kernel eigenstructure.

SRGe J194401.8+284452 is the brightest point-like X-ray object within the position uncertainty ellipse of an unidentified $\gamma$-ray source 4FGL J1943.9+2841. We performed multi-wavelength spectral and photometric studies to determine its nature and possible association with the $\gamma$-ray source. We firmly established its optical counterpart with the Gaia based distance of about 415 pc. Our data show that the object is a cataclysmic variable with an orbital period of about 1.5 hours. SRGe J194401.8+284452 exhibits fast spontaneous transitions between the high and low luminosity states simultaneously in the optical and X-rays, remaining relatively stable between the transitions on scales of several months/years. This can be caused by an order of magnitude changes in the accretion rate. The brightness of the source is about 17 mag and 20 mag in the optical range and $5\times 10^{-12}$ and $5\times 10^{-13}$ erg/cm$^2$/s in the $0.3- 10$ keV range in the high and low states, respectively. We constrained the mass of the white dwarf ($0.3 - 0.9$ $M_\odot$) and its temperature in the low state (14750 $\pm$ 1250 K), the mass of the donor star ($\leq$ 0.08 $\pm$ 0.01 $M_ \odot$). In the low state, we detected regular optical pulsations with an amplitude of 0.2 mag and a period of 8 min. They are likely associated with the spin of the white dwarf, rather than with its non-radial pulsations. In the high state, the object demonstrates only stochastic optical brightness variations on time scales of $1 - 15$~minutes with amplitudes of $0.2 - 0.6$~mag. We conclude, that SRGe J194401.8+284452 can be classified as an intermediate polar, and its association with the $\gamma$-ray source is very unlikely.

HCN molecules serve as an important tracer for chemical evolution of elemental nitrogen in the regions of star and planet formation. This is largely explained by the fact that N atoms and N$_2$ molecules are poorly accessible for the observation in the radio and infrared ranges. In turn, gas-phase HCN can be observed at various stages of star formation including disks arounds young stars, cometary comas and atmospheres of the planetary satellites. Despite the large geography of gas-phase observations, an identification of interstellar HCN ice is still lacking. In this work we present a series of infrared spectroscopic measurements performed at the new ultra-high vacuum cryogenic apparatus aiming to facilitate the search for interstellar HCN ice. A series of high resolution laboratory infrared spectra of HCN molecules embedded in the H$_2$O, H$_2$O:NH$_3$, CO, CO$_2$ and CH$_3$OH ices at 10~K temperature is obtained. These interstellar ice analogues aim to simulate the surroundings of HCN molecules by the main constituents of the icy mantles on the surface of the interstellar grains. In addition, the spectra of HCN molecules embedded in the solid C$_6$H$_6$, C$_5$H$_5$N and C$_6$H$_5$NH$_2$ are obtained to somehow simulate the interaction of HCN molecules with carbonaceous material of the grains rich in polycyclic aromatic hydrocarbons. The acquired laboratory spectroscopic data are compared with the publicly available results of NIRSpec James Webb Space Telescope observations towards quiescent molecular clouds performed by the ICEAge team., Comment: 10 pages, 6 figures, accepted to ApJL

Every continuous map between two compact Riemannian manifolds is homotopic to a harmonic map (HM). We show that a similar situation holds for continuous maps between a post-critically finite (p.c.f.) fractal and a circle. Specifically, we provide a geometric proof of Strichartz's theorem stating that for a given degree and appropriate boundary conditions there is a unique HM from the Sierpinski Gasket (SG) to a circle. Furthermore, we extend this result to HMs on p.c.f. fractals. Our method uses covering spaces for the SG, which are constructed separately for HMs of a given degree, thus capturing the topology intrinsic to each homotopy class. After lifting continuous functions on the SG with values in the unit circle to continuous real-valued functions on the covering space, we use the harmonic extension algorithm to obtain a harmonic function on the covering space. The desired HM is obtained by restricting the domain of the resultant harmonic function to the fundamental domain and projecting the range to the circle. We show that with suitable modifications the method applies to p.c.f. fractals, a large class of self-similar domains. We illustrate our method of constructing the HMs using numerical examples of HMs from the SG to the circle and discuss the construction of the covering spaces for several representative p.c.f. fractals, including the 3-level SG, the hexagasket, and the pentagasket., Comment: 25 pages, 15 figures

Dark matter particles were suggested to have an electric charge smaller than the elementary charge unit $e$. The behavior of such a medium is similar to a collisionless plasma. In this paper, we set new stringent constraints on the charge and mass of the millicharged dark matter particle based on observational data on the Bullet X-ray Cluster., Comment: (6 pages, 1 figure)

Although polymers are widely used in laser-irradiation research, their microscopic response to high-intensity ultrafast XUV or X-ray irradiation is still largely unknown. Here we comparatively study homologous series of alkenes. XTANT-3 hybrid simulation toolkit is used to determine their damage kinetics and irradiation threshold doses. The code simultaneously models the nonequilibrium electron kinetics, the energy transfer between electrons and atoms via nonadiabatic electron-ion (electron-phonon) coupling, nonthermal modification of the interatomic potential due to electronic excitation, and the ensuing atomic response and damage formation. It is shown that the lowest damage threshold is associated with local defect creation such as dehydrogenation, various group detachment from the backbone, or polymer strand cross-linking. At higher doses, the disintegration of the molecules leads to a transient metallic liquid state. We identify nonthermal effects as the leading mechanism of damage, whereas the thermal (electron-ion coupling) channel influences the kinetics only slightly in the case of femtosecond-pulse irradiation. Despite notably different properties of the studied alkene polymers, the ultrafast-X-ray damage threshold doses are found to be very close to ~0.05 eV/atom in all three materials: polyethylene, polypropylene, and polybutylene.

Self-portraits captured from a short distance might look unnatural or even unattractive due to heavy distortions making facial features malformed, and ill-placed head poses. In this paper, we propose SUPER, a novel method of eliminating distortions and adjusting head pose in a close-up face crop. We perform 3D GAN inversion for a facial image by optimizing camera parameters and face latent code, which gives a generated image. Besides, we estimate depth from the obtained latent code, create a depth-induced 3D mesh, and render it with updated camera parameters to obtain a warped portrait. Finally, we apply the visibility-based blending so that visible regions are reprojected, and occluded parts are restored with a generative model. Experiments on face undistortion benchmarks and on our self-collected Head Rotation dataset (HeRo), show that SUPER outperforms previous approaches both qualitatively and quantitatively, opening new possibilities for photorealistic selfie editing.

At ambient conditions, SiC is known to be resistant to irradiation with swift heavy ions (SHI) decelerating in the electronic stopping regime. However, there is no experimental data on the SiC irradiation at elevated temperatures. To investigate this problem, we evaluate the stability of SiC to SHI impacts at high temperatures up to 2200 K. We apply the combination of the Monte-Carlo code TREKIS-3, describing excitation of the electronic and atomic systems using temperature-dependent scattering cross-sections, with molecular-dynamic modeling of the lattice response to the excitation. We demonstrate that increasing irradiation temperature increases the energy transferred to the atomic lattice from the excited electronic system. This material heating leads to formation of a stable nanometric damaged core along the trajectory of 710 MeV Bi ion when the irradiation temperature overcomes the threshold of ~1800 K. In this case, a chain of nanometric voids along the ion trajectory forms due to the mass transport from the track core by edge dislocations. Voids of larger sizes appear at higher irradiation temperatures. At lower irradiation temperatures, the damaged regions recrystallize completely within ~100 ps after the ion passage.

Ultrafast laser radiation or beams of fast charged particles primarily excite the electronic system of a solid driving the target transiently out of thermal equilibrium. Apart from the nonequilibrium between the electrons and atoms, each subsystem may be far from equilibrium. From the first principles, we derive the definition of various atomic temperatures applicable to electronically excited ensembles. It is shown that the definition of the kinetic temperature of atoms in the momentum subspace is unaffected by the excitation of the electronic system. When the electronic temperature differs from the atomic one, an expression for the configurational atomic temperature is proposed, applicable to the electronic-temperature-dependent interatomic potentials (such as ab-initio molecular dynamics simulations). We study how the configurational temperature behaves during nonthermal phase transition, triggered by the evolution of the interatomic potential due to the electronic excitation. It is revealed that upon the ultrafast irradiation, the atomic system of a solid exists temporarily in a multi-temperature state: separate equilibria in the momentum and configurational subspaces. Complete equilibration between the various atomic temperatures takes place at longer timescales, forming the energy equipartition. Based on these results, we propose a formulation of multi-temperature heat transport equations.

We prove that $n$-sphere $\mathbb{S}^n$, $n\geq 2$, admits structurally stable diffeomorphisms $\mathbb{S}^n\to\mathbb{S}^n$ with non-orientable expanding attractors of any topological dimension $d\in\{1,\ldots,[\frac{n}{2}]\}$ where $[x]$ is an integer part of $x$. One proves that $n$-torus $\mathbb{T}^n$, $n\geq 2$, admits structurally stable diffeomorphisms $\mathbb{T}^n\to\mathbb{T}^n$ with orientable expanding attractors of any topological dimension $1\leq q\leq n-1$. We also prove that given any closed $n$-manifold $M^n$, $n\geq 2$, and any $d\in\{1,\ldots,[\frac{n}{2}]\}$, there is an axiom A diffeomorphism $f: M^n\to M^n$ with a $d$-dimensional non-orientable expanding attractor. Similar statements hold for axiom A flows.

We present a model of non-ionizing scattering of electrons on atomic ensemble in matter, applicable in a wide electron energy range from ~eV up to relativistic ones. The approach based on the dynamic-structure factor formalism considers collective response of the atomic and electronic systems of a target. It accounts for dynamical screening of atomic nuclei in matter by valence (collective) and core-shell electrons during the scattering events, dependent on the incident electron velocity. The proposed formalism for the cross section enables us to describe in a unified manner the electron scattering on the ensemble of isolated atomic nuclei at high incident electron energies, reducing to the scattering on phonons with decrease of the energy. Our model can be used, e.g., in transport Monte Carlo codes to describe the energy exchange between excited electrons and atomic ensemble in matter. An example of swift heavy ion track formation in quartz simulated with the proposed cross section shows a reasonable agreement with the experiment validating the model.

The $W$-random graphs provide a flexible framework for modeling large random networks. Using the Large Deviation Principle (LDP) for $W$-random graphs from [9], we prove the LDP for the corresponding class of random symmetric Hilbert-Schmidt integral operators. Our main result describes how the eigenvalues and the eigenspaces of the integral operator are affected by the large deviations in the underlying random graphon. To prove the LDP, we demonstrate continuous dependence of the spectral measures associated with integral operators on the underlying graphons and use the Contraction Principle. To illustrate our results, we obtain leading order asymptotics of the eigenvalues of the integral operators corresponding to certain random graph sequences. These examples suggest several representative scenarios of how the eigenvalues and the eigenspaces of the integral operators are affected by large deviations. Potential implications of these observations for bifurcation analysis of Dynamical Systems and Graph Signal Processing are indicated., Comment: 17 pages

We introduce the DREAMS project, an innovative approach to understanding the astrophysical implications of alternative dark matter models and their effects on galaxy formation and evolution. The DREAMS project will ultimately comprise thousands of cosmological hydrodynamic simulations that simultaneously vary over dark matter physics, astrophysics, and cosmology in modeling a range of systems -- from galaxy clusters to ultra-faint satellites. Such extensive simulation suites can provide adequate training sets for machine-learning-based analyses. This paper introduces two new cosmological hydrodynamical suites of Warm Dark Matter, each comprised of 1024 simulations generated using the Arepo code. One suite consists of uniform-box simulations covering a $(25~h^{-1}~{\rm M}_\odot)^3$ volume, while the other consists of Milky Way zoom-ins with sufficient resolution to capture the properties of classical satellites. For each simulation, the Warm Dark Matter particle mass is varied along with the initial density field and several parameters controlling the strength of baryonic feedback within the IllustrisTNG model. We provide two examples, separately utilizing emulators and Convolutional Neural Networks, to demonstrate how such simulation suites can be used to disentangle the effects of dark matter and baryonic physics on galactic properties. The DREAMS project can be extended further to include different dark matter models, galaxy formation physics, and astrophysical targets. In this way, it will provide an unparalleled opportunity to characterize uncertainties on predictions for small-scale observables, leading to robust predictions for testing the particle physics nature of dark matter on these scales., Comment: 28 pages, 8 figures, DREAMS website: https://www.dreams-project.org

We propose a high precision algorithm for solving the Gelfand-Levitan-Marchenko equation. The algorithm is based on the block version of the Toeplitz Inner-Bordering algorithm of Levinson's type. To approximate integrals, we use the high-precision one-sided and two-sided Gregory quadrature formulas. Also we use the Woodbury formula to construct a computational algorithm. This makes it possible to use the almost Toeplitz structure of the matrices for the fast calculations.

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.

We discuss an algorithm whereby the massive galaxy clusters detected in the SRG/eROSITA all-sky survey are identified and their photometric redshifts are estimated. For this purpose, we use photometric redshift estimates for galaxies and WISE forced photometry. To estimate the algorithm operation quality, we used a sample of 634 massive galaxy clusters from the Planck survey with known spectroscopic redshifts in the range $0.1 < z_{spec} < 0.6$. The accuracy of the photometric redshift estimates for this sample is $\delta z_{phot}/(1+z_{phot}) \approx 0.5$%, the fraction of large deviations is 1.3%. We show that these large deviations arise mainly from the projections of galaxy clusters or other large-scale structures at different redshifts in the X-ray source field. Measuring the infrared (IR) luminosities of galaxy clusters allows one to estimate the reliability of the optical identification of the clusters detected in the SRG/eROSITA survey and to obtain an additional independent measurement of their total gravitational masses, $M_{500}$. We show that the masses $M_{500}$ of the galaxy clusters estimated from their IR luminosity measurements have an accuracy $\sigma_{\lg\,M_{500}} = 0.124$, comparable to the accuracy of the mass estimation for the galaxy clusters from their X-ray luminosities.

The Impulsive Goodwin's Oscillator (IGO) is a mathematical model of a hybrid closed-loop system. It arises by closing a special kind of continuous linear positive time-invariant system with impulsive feedback, which employs both amplitude and frequency pulse modulation. The structure of IGO precludes the existence of equilibria, and all its solutions are oscillatory. With its origin in mathematical biology, the IGO also presents a control paradigm useful in a wide range of applications, in particular dosing of chemicals and medicines. Since the pulse modulation feedback mechanism introduces significant nonlinearity and non-smoothness in the closedloop dynamics, conventional controller design methods fail to apply. However, the hybrid dynamics of IGO reduce to a nonlinear, time-invariant discrete-time system, exhibiting a one-to-one correspondence between periodic solutions of the original IGO and those of the discrete-time system. The paper proposes a design approach that leverages the linearization of the equivalent discrete-time dynamics in the vicinity of a fixed point. A simple and efficient local stability condition of the 1-cycle in terms of the characteristics of the amplitude and frequency modulation functions is obtained., Comment: extended version of the conference paper, accepted by IEEE CDC 2024

Let $M^n$, $n\geq 3$, be a closed orientable $n$-manifold and $\mathbb{D}_k(M^n;a,b,c)$ the set of axiom A diffeomorp\-hisms $f: M^n\to M^n$ satisfying the following conditions: (1) $f$ has $k\geq 1$ nontrivial basic sets each is either an orientable codimension one expanding attractor or an orientable codimension one contracting repeller, and other trivial basic sets which are $a$ sinks, $b$ sources, $c$ saddles; (2) the invariant manifolds of isolated saddles are intersected transversally. We classify the diffeomorphisms from $\mathbb{D}_k(M^n;a,b,c)$ up to the global conjugacy on non-wandering sets for the following subsets $\mathbb{S}_k(M^n;a,b,c), \mathbb{P}_k(M^n;0,0,1), \mathbb{M}_k(M^n;0,0,1)$ of $\mathbb{D}_k(M^n;a,b,c)$ where $\mathbb{S}_k(M^n;a,b,c)$ satisfies to the following conditions: ($1_{\mathbb{S}}$) every nontrivial basic set of any $f\in\mathbb{S}_k(M^n;a,b,c)$ is uniquely bunched, and there is at least one nontrivial attractor and at least one nontrivial repeller, i.e. $k\geq 2$; ($2_{\mathbb{S}}$) $c\geq 1$ and all isolated saddles have the same Morse index belonging to $\{1,n-1\}$. The subset $\mathbb{P}_k(M^n;0,0,1)\subset\mathbb{D}_k(M^n;0,0,1)$ satisfies to the following conditions: ($1_{\mathbb{P}}$) any boundary point of $f\in\mathbb{P}_k(M^n;0,0,1)$ is fixed; ($2_{\mathbb{P}}$) a unique isolated saddle has Morse index different from $\{1,n-1\}$. The subset $\mathbb{M}_k(M^n;0,0,1)\subset\mathbb{D}_k(M^n;0,0,1)$ satisfies to the following conditions: ($1_{\mathbb{M}}$) any boundary point of $f\in\mathbb{M}_k(M^n;0,0,1)$ is fixed; ($2_{\mathbb{M}}$) a unique isolated saddle has Morse index belonging to $\{1,n-1\}$. The classification is based on a description of topological structure of supporting manifolds $M^n$.

Force-free electrodynamics is the theoretical paradigm used to describe electromagnetic fields in a region where the inertia of plasma is negligible compared to the strength of the electromagnetic field. While these fields are studied extensively around accreting black holes in an attempt to describe energy extraction, force-free fields also routinely appear in the study of cosmological magnetic fields. Despite this, there are no systematic studies of exact force-free fields in an expanding universe. In this paper, we use geometric methods to find a wide variety of force-free solutions in a fixed Friedmann-Lemaitre-Robertson-Walker metric background. The method we use can be directly generalized to any arbitrary electrically neutral space-time, and hence, provides a powerful tool to study force-free fields in general.

The latest experimental [Noll et al. Atmos. Chem. Phys. 20(2020)5269] and theoretical [Brooke et al. J. Quant. Spectr. Rad. Transfer 168(2016)142] data on the OH emission intensities are analyzed with use of the NIDL. It is found that the calculated intensities of the $\Delta v>6$ transitions should not be trusted. The analysis of the OH data revealed that the NIDL theory is not applicable to the satellite bands. The effect of small reduced mass previously discovered in H$_2$ [Ushakov et al. J. Mol. Spectrosc. 399(2024)111863], causing the NIDL straight-line slope to be larger than the one associated with the repulsive branch of the potential, is demonstrated, and the same should be true of all the diatomic hydrides. We performed ab initio calculations of the OH repulsive branch and compared it with the one of Brooke et al. and the other due to Varandas and Voronin [Chem. Phys. 194(1995)91]. We found that the ab initio PEF closely follows the Varandas-Voronin potential in the repulsive region important for calculating the overtone intensities [Medvedev, J. Chem. Phys. 137(2012)174307]. Assumption is made that different potentials can be used to calculate transition frequencies and intensities for spectroscopic databases., Comment: 12 pages, 4 figures

This contribution presents the recent research developments within the Cosmic Ray Extremely Distributed Observatory (CREDO) in the search for resolution of various scientific puzzles, ranging from fundamental physical questions to applications like the determination of earthquake precursors. The state-of-the art theoretical, numerical and computational aspects of these phenomena are addressed, as well as recent experimental developments for detection., Comment: 9 pages, 7 figures. Based on the contribution to the XVIII Mexican Workshop on Particles and Fields in Puebla, Mexico, November 2022. M\'exico