Search

The Gaia mission has triggered major developments in the field of Galactic dynamics in recent years, which we discuss in this review. The structure and kinematics of all Galactic components - disc, bar/bulge and halo - are now mapped in great detail not only in the Solar neighbourhood, but across a large part of the Milky Way. The dramatic improvements in the coverage and precision of observations revealed various disequilibrium processes, such as perturbations in the Galactic disc and the deformations of the outer halo, which are partly attributed to the interaction with satellite galaxies. The knowledge of the gravitational potential at all scales has also advanced considerably, but we are still far from having a consistent view on the key properties of the Galaxy, such as the bar pattern speed or the mass profile and shape of the dark halo. The complexity and interplay of several dynamical processes makes the interpretation of observational data challenging, and it is fair to say that more theoretical effort is needed to fully reap the fruit of the Gaia revolution., Comment: Accepted review article in the special issue of New Astronomy Reviews "Gaia, the first crop of discoveries"

We present experimental results of characterization of Silicon photomultipliers (SiPM) in a temperature range from 90~mK to 40~K. Two SiPMs, one from ONSEMI and one from Hamamatsu Photonics were tested. Operating voltage ranges, dark count rates, afterpulsing effects and photon detection efficiencies (PDE) were determined with illumination by 275 and 470~nm light fed into the cryostat via an optical fiber. A cryogenic shutter provided a true dark condition, where thermal radiation from room temperature is shielded and the thermal excitations in the chips are frozen. A second tunneling breakdown was observed at this condition, which substantially limits the operating voltage range for the temperatures 20-30 K. Below $\sim$5 K, both SiPMs recover to an operating over-voltage range of 3-5 V. We found the chips function through the entire tested temperature range, and are capable of withstanding thermal cycling with no major performance degradation., Comment: 10 pages, 8 figures

We present a design and performance tests of an intense source of cold hydrogen atoms for loading large magnetic traps. Our source is based on a cryogenic dissociator of molecular hydrogen at 0.6 K followed by a series of thermal accommodators at 0.5, 0.2 and 0.13 K with inner surfaces covered by a superfluid helium film. All components are thermally anchored to corresponding stages of a dilution refrigerator. The source provides a continuous flux of 7$\cdot$$10^{13}$ H atoms/s in a temperature range of 130-200 mK. We have successfully used the source for loading a large Ioffe-Pritchard magnetic trap recently built in our laboratory [arXiv:2108.09123 or Rev. Sci. Instr. 93 (2), 023201 (2022)]. Calorimetric measurements of the atomic recombination heat allow reliable determination of the atomic flux and H gas density in the trap. We have tested the performance of the source and loading of H atoms into the trap at various configurations of the trapping field, reducing the magnetic barrier height to 75% and 50% of the nominal value of 0.8 T (0.54 K) as well as at the open configuration of the trap at its lower end, when the atoms are in contact with the trapping cell walls covered by a superfluid helium film. In the latter case, raising the trapping cell temperature to 200-250 mK, the low-field seeking atoms at densities exceeding 10$^{11}$ cm$^{-3}$ can be stored for the time over 1000 s, sufficiently long for experiments on precision spectroscopy of cold H gas.

Solid-state synthesis is widely used in exploratory research to study various structural modifications that affect the properties (critical temperature, critical current density, irreversibility field, etc.) of superconductors. The popularity of this method is due to its relative simplicity and availability of the necessary equipment. Combining solid-state synthesis and top-seeded melt growth allows us to increase the grain size in a Tm- and Nd-based 1-2-3 superconductor. Samples with a grain size up to 0.1 mm have been obtained. X-ray diffraction, scanning electron microscopy and magnetization measurements have been used for investigating this superconducting material. The magnetization width {\Delta}M has increased significantly in the synthesized samples. However the temperature dependence of the intragrain critical current density and the pinning force scaling give evidences that the pinning mechanism in the obtained superconductor is essentially the same as in polycrystalline superconductors synthesized by standard solid-state technology. The increase in grain size in the synthesized samples is the main reason for the high values of {\Delta}M., Comment: 12 pages, 7 figures

The dynamics of the Earth's outer radiation belt, filled by energetic electron fluxes, is largely controlled by electron resonant interactions with electromagnetic whistler-mode waves. The most coherent and intense waves resonantly interact with electrons nonlinearly, and the observable effects of such nonlinear interactions cannot be described within the frame of classical quasi-linear models. This paper provides an overview of the current stage of the theory of nonlinear resonant interactions and discusses different possible approaches for incorporating these nonlinear interactions into global radiation belt simulations. We focused on observational properties of whistler-mode waves and theoretical aspects of electron nonlinear resonant interactions between such waves and energetic electrons.

A comparative analysis of two types of dielectric laser accelerators (DLA) based on periodic (grating) and flat dielectric structures to accelerate electrons in the energy range from 300 keV to 3 GeV is presented. The main attention is paid to the conditions, efficiency and restrictions of each acceleration method, as well as the influence of laser radiation parameters on electron acceleration processes. Single and double (both grating and flat) dielectric structures and their impact on acceleration are considered. For the study of two types of quartz DLA, the Ti:Sa laser system with a generation band width 790-810 nm (FWHM), the laser electric field 6 GeV/m are used. The study showed that a flat dielectric structure provides more effective acceleration in a wide range of energies, especially with a symmetrical geometry (double structures), compared with the periodic structure. If we consider only a periodic structure, then with the selected symmetrical geometry, for the ultra relativistic electrons, it demonstrates the acceleration rate two times of magnitude more than for single configuration. However, the use of a one-sided periodic structure turns out to be preferable for accelerating electrons with moderate energies, ~0.5-0.9 MeV, where the acceleration rate in a one-sided configuration is higher than in a symmetric (double) periodic structure. The space-time distributions of laser-excited electromagnetic fields in the accelerating channel and their influence on the electron beam is analyzed also. The advantage of a flat structure over a periodic one, which arises due to the design features of the corresponding dielectric accelerators, is discussed., Comment: 24 pages, 6 figures, 34 references

To search for a conceptual picture describing the magnetization plateau phenomenon, we surveyed the crystal structures and the spin lattices of those magnets exhibiting plateaus in their magnetization vs. magnetic field curves by probing the three questions: (a) why only certain magnets exhibit magnetization plateaus, (b) why there occur several different types of magnetization plateaus, and (c) what controls the widths of magnetization plateaus. We show that the answers to these questions lie in how the magnets under field absorb Zeeman energy hence changing their magnetic structures. The magnetic structure of a magnet insulator is commonly described in terms of its spin lattice, which requires the determination of the spin exchanges nonnegligible strengths between the magnetic ions. Our work strongly suggests that a magnet under magnetic field partitions its spin lattice into antiferromagnetic (AFM) or ferrimagnetic fragments by breaking its weak magnetic bonds. Our supposition of the field-induced partitioning of spin lattice into magnetic fragments is supported by the anisotropic magnetization plateaus of Ising magnets and by the highly anisotropic width of the 1/3-magnetization plateau in azurite. The answers to the three questions (a) - (c) emerge naturally by analyzing how these fragments are formed under magnetic field., Comment: A survey of the magnetization plateau phenomenon; 128 pages including the Supporting Information

Acoustic black holes represent a special class of metastructures allowing efficient absorption based on the slow sound principle. The decrease of the wave speed is associated with the spatial variation of acoustic impedance, while the absorption properties are linked to thermoviscous losses induced by the local resonances of the structure. While most of the developments in the field of sonic black holes are dedicated to one-dimensional structures, the current study is concerned with their two-dimensional counterparts. It is shown that the change of the dimensionality results in the change of noise insulation mechanism, which relies on the opening of band-gaps rather then thermoviscous losses. The formation of band-gaps is associated with the strong coupling between the resonators constituting the considered structures. Numerically and experimentally it is shown than the structure is characterized by broad stop-bands in transmission spectra, while the air flow propagation is still allowed. In particular, a realistic application scenario is considered, in which the acoustic noise and the air flow are generated by a fan embedded into a ventilation duct. The obtained results pave the way towards the development of next-level ventilated metamaterials for efficient noise control.

Deep neural network models have a complex architecture and are overparameterized. The number of parameters is more than the whole dataset, which is highly resource-consuming. This complicates their application and limits its usage on different devices. Reduction in the number of network parameters helps to reduce the size of the model, but at the same time, thoughtlessly applied, can lead to a deterioration in the quality of the network. One way to reduce the number of model parameters is matrix decomposition, where a matrix is represented as a product of smaller matrices. In this paper, we propose a new way of applying the matrix decomposition with respect to the weights of convolutional layers. The essence of the method is to train not all convolutions, but only the subset of convolutions (basis convolutions), and represent the rest as linear combinations of the basis ones. Experiments on models from the ResNet family and the CIFAR-10 dataset demonstrate that basis convolutions can not only reduce the size of the model but also accelerate the forward and backward passes of the network. Another contribution of this work is that we propose a fast method for selecting a subset of network layers in which the use of matrix decomposition does not degrade the quality of the final model., Comment: Increase the size of matrix pictures for better UX in PDF view

Due to observational challenges, the mass function of black holes (BH) at lower masses is poorly constrained in the local universe. Understanding the occupation fraction of BHs in low-mass galaxies is crucial for constraining the origins of supermassive BH seeds. Compact stellar systems (CSSs), including ultra-compact dwarf galaxies (UCDs) and compact elliptical galaxies (cEs), are potential intermediate-mass BH hosts. Despite the difficulties posed by their limited spheres of influence, stellar dynamical modeling has been effective in estimating central BH masses in CSSs. Some CSSs may harbor a BH constituting up to 20% of their host stellar mass, while others might not have a central BH. In support of our ongoing efforts to determine the BH masses in select CSSs in the Virgo cluster using JWST/NIRSpec IFU observations and orbit-superposition dynamical models, we create mock kinematic data mimicking the characteristics of observed cEs/UCDs in the Virgo cluster with different BH masses. We then construct a series of dynamical models using the orbit-superposition code FORSTAND and explore the accuracy of recovering the BH mass. We find that the mass of BHs comprising 1% or more of the total host stellar mass can be accurately determined through kinematic maps featuring higher-order velocity moments. We also assess how BH mass measurement is affected by deprojection methods, regularization factors, anisotropy parameters, orbit initial conditions, the absence of higher-order velocity moments, spatial resolution, and the signal-to-noise ratio., Comment: 18 pages, 14 figures, Accepted for publication in ApJ

A comprehensive numerical modelling of microcavity parameters for micropillar lasers with optical pumping was presented. The structure with a hybrid dielectric-semiconductor top mirror has a significantly higher calculated quality-factor (~65000 for 5 $\mu$m pillar) due to better vertical mode confinement. The minimum laser threshold (~370 $\mu$W for 5 $\mu$m pillar) coincided with a temperature of 130 K, which is close to zero gain to cavity detuning. Lasing up to 220 K was demonstrated with a laser threshold of about 2.2 mW.

A low energy particle confined by a horizontal reflective surface and gravity settles in gravitationally bound quantum states. These gravitational quantum states (GQS) were so far only observed with neutrons. However, the existence of GQS is predicted also for atoms. The GRASIAN collaboration pursues the first observation of GQS of atoms, using a cryogenic hydrogen beam. This endeavor is motivated by the higher densities, which can be expected from hydrogen compared to neutrons, the easier access, the fact that GQS were never observed with atoms and the accessibility to hypothetical short range interactions. In addition to enabling gravitational quantum spectroscopy, such a cryogenic hydrogen beam with very low vertical velocity components - a few cm s$^{-1}$, can be used for precision optical and microwave spectroscopy. In this article, we report on our methods developed to reduce background and to detect atoms with a low horizontal velocity, which are needed for such an experiment. Our recent measurement results on the collimation of the hydrogen beam to 2 mm, the reduction of background and improvement of signal-to-noise and finally our first detection of atoms with velocities < 72 m s$^{-1}$ are presented. Furthermore, we show calculations, estimating the feasibility of the planned experiment and simulations which confirm that we can select vertical velocity components in the order of cm s$^{-1}$.

A tracer sample in a gravitational potential, starting from a generic initial condition, phase-mixes towards a stationary state. This evolution is accompanied by an entropy increase, and the final state is characterized by a distribution function (DF) that depends only on integrals of motion (Jeans theorem). We present a method to constrain a gravitational potential where a sample is stationary by minimizing the entropy the sample would have if it were allowed to phase-mix in trial potentials. This method avoids assuming a known DF, and is applicable to any sets of integrals. We provide expressions for the entropy of DFs depending on energy, $f(E)$, energy and angular momentum, $f(E,L)$, or three actions, $f(\vec{J})$, and investigate the bias and fluctuations in their estimates. We show that the method correctly recovers the potential parameters for spherical and axisymmetric models. We also present a methodology to characterize the posterior probability distribution of the parameters with an Approximate Bayesian Computation, indicating a pathway for application to observational data. Using $N=10^4$ tracers with $20\%$-uncertainties in the 6D coordinates, we recover the flattening parameter $q$ of an axisymmetric potential with $\sigma_q/q\sim 10\%$., Comment: Significant changes in appendix with mathematical results. Final expressions and numerical results are the same. A couple of discussions subsections added, and a new appendix on the possibility of maximizing an entropy in angle-space. Submitted to ApJ

Motivated by the need for realistic, dynamically self-consistent, evolving galaxy models that avoid the complexity of full, and zoom-in, cosmological simulations, we have developed NEXUS, an integral framework to create and evolve synthetic galaxies made of collisionless and gaseous components. NEXUS leverages the power of publicly available, tried-and-tested packages: the stellar-dynamics, action-based library AGAMA; and the adaptive mesh refinement, N-body/hydrodynamical code RAMSES, modified to meet our needs. In addition, we make use of a proprietary module to account for galaxy formation physics, including gas cooling and heating, star formation, stellar feedback, and chemical enrichment. NEXUS' basic functionality consists in the generation of bespoke initial conditions (ICs) for a diversity of galaxy models, which are advanced in time to simulate the galaxy's evolution. The fully self-consistent ICs are generated with a distribution-function based approach, as implemented in the galaxy modelling module of AGAMA -- up to now restricted to collisionless components, extended in this work to treat two types of gaseous configurations: hot halos and gas discs. NEXUS allows constructing equilibrium models with disc gas fractions $0~\leq~f_{\rm gas}~\leq~1$, appropriate to model both low- and high-redshift galaxies. Similarly, the framework is ideally suited to the study of galactic ecology, i.e. the dynamical interplay between stars and gas over billions of years. As a validation and illustration of our framework, we reproduce several isolated galaxy model setups reported in earlier studies, and present a new, `nested bar' galaxy simulation. Future upgrades of NEXUS will include magneto-hydrodynamics and highly energetic particle (`cosmic ray') heating., Comment: MNRAS accepted

The emergence and rapid development of the open RISC-V instruction set architecture opens up new horizons on the way to efficient devices, ranging from existing low-power IoT boards to future high-performance servers. The effective use of RISC-V CPUs requires software optimization for the target platform. In this paper, we focus on the RISC-V-specific optimization of the CatBoost library, one of the widely used implementations of gradient boosting for decision trees. The CatBoost library is deeply optimized for commodity CPUs and GPUs. However, vectorization is required to effectively utilize the resources of RISC-V CPUs with the RVV 0.7.1 vector extension, which cannot be done automatically with a C++ compiler yet. The paper reports on our experience in benchmarking CatBoost on the Lichee Pi 4a, RISC-V-based board, and shows how manual vectorization of computationally intensive loops with intrinsics can speed up the use of decision trees several times, depending on the specific workload. The developed codes are publicly available on GitHub.

We analyse higher-spin theory with general coupling constant $\eta$ at the second order, focusing on the gauge non-invariant vertices $\Upsilon(\omega,\omega)$, $\Upsilon(\Omega,\omega,C)$ and $\Upsilon(\omega,C)$, that are shown to generate nontrivial currents in the Fronsdal equations. Explicit expressions for the currents are found in the frame-like formalism counterpart of the TT gauge worked out in the paper. The nonlinear higher-spin theory is shown to generate all types of Metsaev's currents with the coupling constants manifestly expressed via the complex coupling constant $\eta$ of the higher-spin theory. It is shown that all currents in the higher-spin theory are conformal in the TT gauge except for those bilinear in the higher-spin gauge fields $\omega$., Comment: 47 pages; V2: minor corrections, acknowledgement added, matches the published version

The decrease rate of dust mass due to strong shock waves ($v_s\geq 150$ km s$^{-1}$) from supernovae (SNe) estimated for the Milky Way interstellar medium significantly exceeds the overall production rate by both asymptotic giant branch stars and core collapse SNe. The interplay between the production and destruction rates is critically important for evaluation of the net dust outcome from SNe at different conditions. In light of this, we study the dynamics of initially polydisperse dust grains pre-existing in an ambient medium swept up the SN shock front depending on magnitude of inhomogeneity (clumpiness) in the medium. We find that dust destruction inside the bubble is inhibited in more inhomogeneous medium: the larger amount of dust survives for the higher dispersion of density. This trend is set by the interrelation between radiative gas cooling and dust sputtering in different environment. After several radiative times the mass fraction of the survived dust saturates at the level almost independent on the gas mean density. We note that for more clumpy medium the distributions of dust over thermal phases of a gas inside the bubble and over sizes are smoother and flatter in comparison with those in a nearly homogeneous medium., Comment: 13 pages, 12 figures, New Astronomy in press

Brillouin light scattering (BLS) spectroscopy is a powerful tool for detecting spin waves in magnetic thin films and nanostructures. Despite comprehensive access to spin-wave properties, BLS spectroscopy suffers from the limited wavenumber of detectable spin waves and the typically relatively low sensitivity. In this work, we present the results of numerical simulations based on the recently developed analytical model describing plasmon-enhanced BLS. The effective susceptibility is defined for a single plasmonic nanoparticle in the shape of an ellipsoid of rotation, for the sandwiched plasmonic nanoparticles separated by a dielectric spacer, as well as for the array of plasmonic resonators on the surface of a magnetic film. It is shown that the eccentricity of the metal nanoparticles, which describes their shape, plays a key role in the enhancement of the BLS signal. The optimal conditions for BLS enhancement are numerically defined for gold and silver plasmon systems for photons of different energies. The presented results define the roadmap for the experimental realization of plasmon-enhanced BLS spectroscopy., Comment: 29 pages, 23 formulas, 17 figures

The destruction of clouds by strong shocks and hot winds is the key process responsible for the transp orting of metals and dust from the ISM to the ICM/IGM, and establishing the multiphase structure in and around galaxies. In this work, we perform a detailed analysis of this process using two different approaches for tracking the cloud material (gas and dust): the so-called 'colored' fluid, and the Lagrangian (trace) particles. We find that for the clouds in the hot phase ($T>10^5$ K), the two methods produce significantly different mass fractions and velocities of the cloud material. In contrast, the two methods produce similar results for the clouds that are in the warm/cold phases ($T < 10^5$ K). We find that the Kelvin--Helmholtz instability is suppressed in the warm clouds of size $\sim$100 pc and metallicity $Z\gt 0.1 Z_\odot$ due to effective gas cooling. This causes a delay in the destruction of such clouds that are interacting with the hot ICM flow. We demonstrate that the dust particles that are evacuated from their 'parent' clouds to the hot medium show different dynamics when compared to that of the Lagrangian (trace) particles. Our results indicate that the dust grains swept out to the hot gas are destroyed., Comment: 15 pages, 7 figures

For understanding the nature of gaseous flows in star-forming regions of nearby galaxies it is usually utilized the relation between surface brightness in H$\alpha$ line and velocity dispersion of ionized gas known as ''surface brightness -- velocity dispersion diagram''. Using the three-dimensional gasdynamic simulations we consider the evolution of the synthetic diagrams for supershells driven by multiple supernova explosions in stellar cluster located in the galactic disk. We investigate the shape and structure of the diagrams depending on gaseous density and metallicity, disk scale height values. We show that there are several loci of values typical for young bubbles evolved in dense or rarefied gas at large heights above the disk midplane. We find that the structure of the diagram is depended on age of a supershell and physical conditions of a gas in the disk. We argue that the diagrams obtained for the nearby dwarf galaxies can be interpreted by only using the dynamics of bubbles driven by multiple supernova explosions in low-mass stellar clusters of different age., Comment: 12 pages, 4 figures

Obtaining reliable distance estimates to gas clouds within the Milky Way is challenging in the absence of certain tracers. The kinematic distance approach has been used as an alternative, derived from the assumption of circular trajectories around the Galactic centre. Consequently, significant errors are expected in regions where gas flow deviates from purely circular motions. We aim to quantify the systematic errors that arise from the kinematic distance method in the presence of a Galactic potential that is non-axisymmetric. We investigate how these errors differ in certain regions of the Galaxy and how they relate to the underlying dynamics. We perform 2D hydrodynamical simulation of the gas disk with the moving-mesh code Arepo, adding the capability of using an external potential provided by the Agama library for galactic dynamics. We introduce a new analytic potential of the Milky Way, taking elements from existing models and adjusting parameters to match recent observational constraints. In line with results of previous studies, we report significant errors in the kinematic distance estimate for gas close to the Sun, along sight lines towards the Galactic centre and anti-centre, and associated with the Galactic bar. Kinematic distance errors are low within the spiral arms as gas resides close to local potential minima and the resulting LOS velocity is similar to what is expected for an axisymmetric potential. Interarm regions exhibit large deviations at any given Galactic radius. This is caused by the gas being sped up or slowed down as it travels into or out of spiral arms. In addition, we identify 'zones of avoidance' in the lv-diagram, where the kinematic distance method is particularly unreliable and should only be used with caution, and we find a power law relation between the kinematic distance error and the deviation of the projected LOS velocity from circular motion., Comment: 23 pages, 20 figures, 6 tables, accepted for publication in A&A

The current major challenge to reconstruct the chronology of the Milky Way (MW) is the difficulty to derive precise stellar ages. CMD-fitting offers an alternative to individual age determinations to derive the star formation history (SFH). We present CMDft.Gaia and use it to analyse the CMD of the Gaia Catalogue of Nearby Stars (GCNS), which contains a census of the stars within 100 pc of the Sun. The result is an unprecedented detailed view of the evolution of the MW disk. The bulk of star formation started 11-10.5 Gyr ago at [Fe/H]~solar and continued with a slightly decreasing metallicity trend until 6 Gyr ago. Between 6-4 Gyr ago, a break in the age-metallicity distribution is observed, with 3 stellar populations with distinct metallicities (sub-solar, solar, and super-solar), possibly indicating some dramatic event in the Galaxy. Star formation resumed 4 Gyr ago with a bursty behaviour, metallicity near solar and higher average SFR. The derived metallicity distribution closely matches precise spectroscopic data, which also show stellar populations deviating from solar metallicity. Interestingly, our results reveal the presence of intermediate-age populations with both a metallicity typical of the thick disk and supersolar metallicity. Our many tests indicate that, with high precision Gaia photometric and distance data, CMDft.Gaia can achieve a precision ~10% and an accuracy better than 6% in the dating of even old stellar populations. The comparison with independent spectroscopic data shows that metallicity distributions are determined with high precision, without imposing a-priory metallicity information. This opens the door to obtaining detailed and robust information on the evolution of the stellar populations of the MW over cosmic time. As an example we provide an unprecedented detailed view of the age and metallicity distributions of the stars within 100 pc of the Sun., Comment: 35 pages, 30 figures; to be published in A&A; revised version after minor referee comments

We study interactions of higher-spin massless fields $\varphi$ with conserved currents multilinear in the off-shell matter fields $\phi$. Specifically, we focus on the 3d case where a slight modification of the $\sigma_-$-cohomology technique developed earlier is directly applicable to control nontriviality of the interaction vertices at the convention that the vertices removable by a local field redefinition of a higher-spin field or having schematic form $F(\varphi) G(\phi)$, where $F(\varphi)$ is a gauge invariant field strength of a free higher-spin field, are called deformationally trivial. It is demonstrated how the $\sigma_-$-cohomology approach can be applied to the analysis of nonlinear vertices. Generally, deformationally trivial vertices are not $\sigma_-$-closed while the deformationally non-trivial ones must be in $H(\sigma_-)$. It is shown that, at least in the $3d$ case, the relevant cohomology group $H^1(\sigma_-)=0$ and, hence, no deformationally non-trivial off-shell vertices exist. On the other hand, there exists an infinite class of deformationally trivial vertices, that includes the vertex recently proposed for spin three. Our analysis goes beyond the higher-spin vertices allowing to show that, at least in three dimensions, nonlinear combinations of the off-shell scalar fields and their derivatives cannot obey non-trivial equations., Comment: 16 pages; V2: typos corrected, minor clarifications added, matches the published version

In this work, we present the studies of structural phase transitions in Fe(Se,Te) crystals in the range of about 30% selenium substitution by tellurium. We found a significant change in the properties of the ordered state of these compositions compared to the case of pure FeSe. The resistivity at low temperatures for the studied Fe(Se,Te) is proportional to the square of the temperature while for pure FeSe below the structural transition it depends almost linearly on temperature. The NMR data show a noticeable line broadening below the structural transition and an anomaly in the temperature dependence of the relaxation rate in the tellurium-substituted compounds, which was not observed in the pure FeSe. This reveals in quasi-binary compounds of iron-based superconductors a region of quantum criticality similar to that which exists when the nematicity of FeSe is suppressed under pressure and which precedes the emergence of high-temperature superconductivity in FeSe under hydrostatic pressure.

Interface engineering is one of the promising strategies for the long-term stabilization of perovskite solar cells, preventing chemical decomposition induced by external agents and promoting fast charge transfer. Recently, MXenes-2D structured transition metal carbides and nitrides with various functionalization (=O,-F,-OH) demonstrated high potential for mastering the work function in halide perovskite absorbers and significantly improved the n-type charge collection in solar cells. This work demonstrates that MXenes allow for efficient stabilization of perovskite solar cells besides improving their performances. We introduce a new mixed composite bathocuproine:MXene, i.e., (BCP:MXene) interlayer at the interface between an electron-transport layer (ETL) and a metal cathode in the p-in device structure. Our investigation demonstrates that the use of BCP:MXene interlayer slightly increases the power conversation efficiency (PCE) for PSCs (from 16.5 for reference to 17.5%) but dramatically improves the out of Glove-Box stability. Under ISOS-L-2 light soaking stress at 63$\pm$ 1.5{\textdegree}C, The T80 (time needed to reduce efficiency down to 80% of the initial one) period increased from 460 h to > 2300 h.

Nowadays, methods and techniques of Machine Learning and Deep Learning are being used in various scientific areas. They help to automatize calculations without losing in quality. In this paper the applying of convolutional neural network was considered in frame of problems from statistical physics and computer simulation of magnetic films. In a frame of the first task, CNN was used to determine critical Curie point for Ising model on 2D square lattice. Obtained results were compared with classical Monte-Carlo methods and exact solution. Systems of various lattice sizes and the influence of the size effect on the results' accuracy were considered. Also, authors considered the classical two-dimensional Heisenberg model, a spin system with direct short-range exchange, and studied of its competition with the Dzyaloshinskii-Moriya interaction. A neural network was applied to the recognition of Spiral (Sp), Spiral-skyrmion (SpSk) Skyrmion (Sk), Skyrmion-ferromagnetic (SkF) and Ferromagnetic (FM) phases of the Heisenberg spin system with magnetic skyrmions. The advantage of CNN's application over conventional methods for determination of skyrmion's phases was revealed., Comment: 6 pages, 3 figures

For the search of the chiral magnetic effect (CME), STAR previously presented the results from isobar collisions (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) obtained through a blind analysis. The ratio of results in Ru+Ru to Zr+Zr collisions for the CME-sensitive charge-dependent azimuthal correlator ($\Delta\gamma$), normalized by elliptic anisotropy ($v_{2}$), was observed to be close to but systematically larger than the inverse multiplicity ratio. The background baseline for the isobar ratio, $Y = \frac{(\Delta\gamma/v_{2})^{\text{Ru}}}{(\Delta\gamma/v_{2})^{\text{Zr}}}$, is naively expected to be $\frac{(1/N)^{\text{Ru}}}{(1/N)^{\text{Zr}}}$; however, genuine two- and three-particle correlations are expected to alter it. We estimate the contributions to $Y$ from those correlations, utilizing both the isobar data and HIJING simulations. After including those contributions, we arrive at a final background baseline for $Y$, which is consistent with the isobar data. We extract an upper limit for the CME fraction in the $\Delta\gamma$ measurement of approximately $10\%$ at a $95\%$ confidence level on in isobar collisions at $\sqrt{s_{\text{NN}}} = 200$ GeV, with an expected $15\%$ difference in their squared magnetic fields., Comment: 19 pages, 14 figures

Explicit expressions for multimatrix models with complex and unitary matrices allows to couple these models with well-known unitary, orthogonsl and sympletic ensembles. We consider examples of such mixed ensembles which are solvable in the sense that the partition functions of such ensembles can be considered as tau functions of the classical integrable equations., Comment: 10 pages

We present a new method to infer the 3D dimensional luminosity distributions of edge-on barred galaxies with boxy-peanut/X (BP/X) shaped structures from their 2D surface brightness distributions. Our method relies on forward modeling of newly introduced parametric 3D density distributions for the BP/X bar, disc and other components using an existing image fitting software package (IMFIT). We validate our method using an N-body simulation of a barred disc galaxy with a moderately strong BP/X shape. For fixed orientation angles the derived 3D BP/X shaped density distribution is shown to yield a gravitational potential that is accurate to at least 5% and forces that are accurate to at least 15%, with average errors being ~1.5% for both. When additional quantities of interest, such as the orientation of the bar to the line-of-sight, its pattern speed, and the stellar mass-to-light ratio are unknown they can be recovered to high accuracy by providing the parametric density distribution to the Schwarzschild modelling code FORSTAND. We also explore the ability of our models to recover the mass of the central supermassive black hole. This method is the first to be able to accurately recover both the orientation of the bar to the line-of-sight and its pattern speed even when the disc is perfectly edge-on., Comment: 23 pages, 16 figures, submitted to MNRAS. Comments are welcome

The development of an open and free RISC-V architecture is of great interest for a wide range of areas, including high-performance computing and numerical simulation in mathematics, physics, chemistry and other problem domains. In this paper, we discuss the possibilities of accelerating computations on available RISC-V processors by improving the vectorization of several computer vision and machine learning algorithms in the widely used OpenCV library. It is shown that improved vectorization speeds up computations on existing prototypes of RISC-V devices by tens of percent.

The chiral magnetic effect (CME) is a phenomenon that arises from the QCD anomaly in the presence of an external magnetic field. The experimental search for its evidence has been one of the key goals of the physics program of the Relativistic Heavy-Ion Collider. The STAR collaboration has previously presented the results of a blind analysis of isobar collisions (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) in the search for the CME. The isobar ratio ($Y$) of CME-sensitive observable, charge separation scaled by elliptic anisotropy, is close to but systematically larger than the inverse multiplicity ratio, the naive background baseline. This indicates the potential existence of a CME signal and the presence of remaining nonflow background due to two- and three-particle correlations, which are different between the isobars. In this post-blind analysis, we estimate the contributions from those nonflow correlations as a background baseline to $Y$, utilizing the isobar data as well as Heavy Ion Jet Interaction Generator simulations. This baseline is found consistent with the isobar ratio measurement, and an upper limit of 10% at 95% confidence level is extracted for the CME fraction in the charge separation measurement in isobar collisions at $\sqrt{s_{\rm NN}}=200$ GeV., Comment: 8 pages, 4 figures

Supernovae (SN) explosions are thought to be an important source of dust in galaxies. At the same time strong shocks from SNe are known as an efficient mechanism of dust destruction via thermal and kinetic sputtering. A critically important question of how these two hypotheses of SNe activity control the dust budget in galaxies is still not quite clearly understood. In this paper we address this question within 3D multi-fluid hydrodynamical simulations, treating separately the SNe injected dust and the dust pre-existed in ambient interstellar gas. We focus primarily on how the injected and the pre-existing dust is destroyed by shock waves and hot gas in the SN bubble depending on the density of ambient gas. Within our model we estimate an upper limit of the SN-produced dust mass which can be supplied into interstellar medium. For a SN progenitor mass of 30 $M_\odot$ and the ejected dust mass $M_d=1~M_\odot$ we constrain the dust mass that can be delivered into the ISM as $\geq 0.13~M_\odot$, provided that the SN has injected large dust particles with $a\geq 0.1~\mu$m., Comment: 13 pages, 12 figures, accepted to MNRAS

Using a notion on the excess entropy of glass with respect to the counterpart crystal, we introduce a simple dimensionless order parameter $\xi$, which changes from $\xi \rightarrow 0$ to $\xi \rightarrow 1$. The former case corresponds to a strongly disordered liquid-like structure while the latter situation describes a highly ordered crystal-like glass. This approach is applied to 13 metallic and 2 tellurite glasses. We found that $\xi$ is strongly sensitive to structural state and/or chemical composition. It can be also used for a comparison of the order in glasses belonging to different classes and appear to represent a new way of structural analysis., Comment: 5 pages, 5 figures

We study intermittent coherent structures in solar wind magnetic turbulence from MHD to kinetic plasma scales using Parker Solar Probe data during its first perihelion (at 0.17 au), when the satellite was in the Alfv\'enic slow wind of 340 km/s. The coherent structures are energetic events localized in time and covering wide range of scales. We detect them using Morlet wavelets. For the first time, we apply a multi-scale analyses in physical space to study these structures. At MHD scales within the inertial range, times scales $\tau \in (1, 10^{2} )$ s, we find (i) current sheets including switchback boundaries and (ii) Alfv\'en vortices. Within these events, there are embedded structures at smaller scales: typically Alfv\'en vortices at ion scales, $\tau \in (0.08, 1)$ s, and a compressible vortices at sub-ion scales, $\tau \in (8,80)$ ms. The number of coherent structures grows toward smaller scales: we observe about $\sim 200$ events during 5 h time interval at MHD scales, $\sim 10^{3}$ events ai ion scales and $\sim 10^{4}$ events at sub-ion scales. In general, there are multiple structures of ion and sub-ion scales embedded within one MHD structure. There are also examples of ion and sub-ion scales structures outside of MHD structures. To quantify the relative importance of different type of structures, we do a statistical comparison of the observed structures with the expectations of models of the current sheets and vortices. This comparison is based on amplitude anisotropy of magnetic fluctuations within the structures. The results show the dominance of Alfv\'en vortices at all scales in contrast to the widespread view of dominance of current sheets. This means that Alfv\'en vortices are important building blocs of solar wind turbulence., Comment: Revised version of the article, accepted for publication in Astrophysical Journal, 30 pages, 15 figures

A new efficient approach to the analysis of nonlinear higher-spin equations, that treats democratically auxiliary spinor variables $Z_A$ and integration homotopy parameters in the non-linear vertices of the higher-spin theory, is developed. Being most general, the proposed approach is the same time far simpler than those available so far. In particular, it is free from the necessity to use the Schouten identity. Remarkably, the problem of reconstruction of higher-spin vertices is mapped to certain polyhedra cohomology in terms of homotopy parameters themselves. The new scheme provides a powerful tool for the study of higher-order corrections in higher-spin theory and, in particular, its spin-locality. It is illustrated by the analysis of the lower order vertices, reproducing not only the results obtained previously by the shifted homotopy approach but also projectively-compact vertices with the minimal number of derivatives, that were so far unreachable within that scheme., Comment: To the memory of Lars Brink, 42 pages; V2: erroneous coefficients and typos fixed, clarifications and acknowledgments added, matches the published version, 43 pages

A chemodynamical model of our galaxy is fitted to data from DR17 of the APOGEE survey supplemented with data from the StarHorse catalogue and gaia DR3. Dynamically, the model is defined by action-based distribution functions for dark matter and six stellar components plus a gas disc. The gravitational potential jointly generated by the model's components is used to examine the galaxy's chemical composition within action space. The observational data probably cover all parts of action space that are populated by stars. The overwhelming majority of stars have angular momentum J_\phi>0 implying that they were born in the Galactic disc. High-alpha stars dominate in a region that is sharply bounded by J_\phi \la J_\phi(solar). Chemically the model is defined by giving each stellar component a Gaussian distribution in ([Fe/H],[Mg/Fe]) space about a mean that is a linear function of the actions. The model's 47 dynamical parameters are chosen to maximise the likelihood of the data given the model in 72 three-dimensional velocity spaces while its 70 chemical parameters are similarly chosen in five-dimensional chemo-dynamical space. The circular speed falls steadily from 237\kms at R=4\kpc to 218\kms at R=20\kpc. Dark matter contributes half the radial force on the Sun and has local density 0.011\msun\pc^{-3}, there being 24.5\msun\pc^{-2} in dark matter and 26.5\msun\pc^{-2} in stars within 1.1\kpc of the plane., Comment: 22 pp accepted by MNRAS

We describe the calibration and imaging heuristics developed and deployed in the ALMA interferometric data processing pipeline, as of ALMA Cycle 9. The pipeline software framework is written in Python, with each data reduction stage layered on top of tasks and toolkit functions provided by the Common Astronomy Software Applications package. This framework supports a variety of tasks for observatory operations, including science data quality assurance, observing mode commissioning, and user reprocessing. It supports ALMA and VLA interferometric data along with ALMA and NRO45m single dish data, via different stages and heuristics. In addition to producing calibration tables, calibrated measurement sets, and cleaned images, the pipeline creates a WebLog which serves as the primary interface for verifying the data quality assurance by the observatory and for examining the contents of the data by the user. Following the adoption of the pipeline by ALMA Operations in 2014, the heuristics have been refined through annual development cycles, culminating in a new pipeline release aligned with the start of each ALMA Cycle of observations. Initial development focused on basic calibration and flagging heuristics (Cycles 2-3), followed by imaging heuristics (Cycles 4-5), refinement of the flagging and imaging heuristics with parallel processing (Cycles 6-7), addition of the moment difference analysis to improve continuum channel identification (2020 release), addition of a spectral renormalization stage (Cycle 8), and improvement in low SNR calibration heuristics (Cycle 9). In the two most recent Cycles, 97% of ALMA datasets were calibrated and imaged with the pipeline, ensuring long-term automated reproducibility. We conclude with a brief description of plans for future additions, including self-calibration, multi-configuration imaging, and calibration and imaging of full polarization data., Comment: Accepted for publication by Publications of the Astronomical Society of the Pacific, 65 pages, 20 figures, 10 tables, 2 appendices. Small corrections and additions from the proof stage have been applied

We propose a scenario in which the Large Magellanic Cloud (LMC) is on its second passage around the Milky Way. Using a series of tailored N-body simulations, we demonstrate that such orbits are consistent with current observational constraints on the mass distribution and relative velocity of both galaxies. The previous pericentre passage of the LMC could have occurred 5-10 Gyr ago at a distance >~100 kpc, large enough to retain its current population of satellites. The perturbations of the Milky Way halo induced by the LMC look nearly identical to the first-passage scenario, however, the distribution of LMC debris is considerably broader in the second-passage model. We examine the likelihood of current and past association with the Magellanic system for dwarf galaxies in the Local Group, and find that in addition to 10-11 current LMC satellites, it could have brought a further 4-6 galaxies that have been lost after the first pericentre passage. In particular, four of the classical dwarfs - Carina, Draco, Fornax and Ursa Minor - each have a ~50% probability of once belonging to the Magellanic system, thus providing a possible explanation for the ``plane of satellites'' conundrum., Comment: Updated to match the published version. Simulation data and scripts provided at https://zenodo.org/record/8015660 , and a movie - at https://people.ast.cam.ac.uk/~vasiliev/WelcomeLMC/movie.mp4

On the basis of shear modulus measurements on a Pt-based glass, we calculated temperature dependence of the defect concentration c using the Interstitialcy theory. This temperature dependence is compared with temperature dependence of the normalized full width at half maximum (FWHM) gamma of the first peak of the structure factor S(q) for the same glass available in the literature. It is found that above the glass transition temperature Tg linearly increases with c in the same way for both initial and relaxed (preannealed) samples providing the evidence of defect-induced disordering in the supercooled liquid region independent of glass thermal prehistory. For both states of the samples, the derivative d(gamma)/dc is close to unity. Below Tg, the interrelation between gamma and c is entirely different for initial and relaxed samples. In the former case, strong defect-induced ordering upon approaching Tg is observed while relaxed samples do not reveal any clear ordering/disordering. Possible reasons for these observations are discussed. To further investigate the relationship between the normalized FWHM and defect concentration, we performed molecular dynamic simulation of gamma(c)-dependence in a high-entropy FeNiCrCoCu model glass. It is found that gamma also linearly increases with c while the derivative d(gamma)/dc is again close to unity just as in the case of Pt-based glass., Comment: 15 pages, 6 postscript figures

Thin galactic discs and nuclear stellar discs (NSDs) are fragile structures that can be easily disturbed by merger events. By studying the age of the stellar populations in present-day discs, we can learn about the assembly history of galaxies and place constraints on their past merger events. Following on the steps of our initial work, we explore the fragility of such disc structures in intermediate-mass-ratio dry encounters using the previously constructed $N$-body model of the Fornax galaxy NGC 1381 (FCC 170), which hosts both a thin galactic disc and a NSD. We dismiss major and minor encounters, as the former were previously shown to easily destroy thin-disc structures, whereas the latter take several Hubble times to complete in the specific case of FCC 170. The kinematics and structure of the thin galactic disc are dramatically altered by the mergers, whereas the NSD shows a remarkable resilience, exhibiting only a smooth increase of its size when compared to the model evolved in isolation. Our results suggest that thin galactic discs are better tracers for intermediate-mass-ratio mergers, while NSDs may be more useful for major encounters. Based on our simulations and previous analysis of the stellar populations, we concluded that FCC 170 has not experienced any intermediate-mass-ratio dry encounters for at least $\sim$10 Gyr, as indicated by the age of its thin-disc stellar populations., Comment: 11 pages, 10 figures

Diamond single crystals showing Infra-red features of pressurized CO2-I phase were studied using Transmission Electron Microscopy (TEM) and tomography. Numerous O-containing precipitates with sizes up to 45 nm are observed. The absolute majority of these precipitates decorate dislocation loops or are located inside them; individual scattered precipitates are also present. Morphology of the precipitates varies from quasi-isometric octahedra to highly flattened elongated ones. Close association of the precipitates with the dislocation loops implies their formation by exsolution of oxygen impurity from diamond lattice; the size distribution of the precipitates suggests that the equilibrium state is not yet reached. Presumably, the morphology and precise chemical composition depend on P-T-t evolution of the diamond crystal and corresponding changes in oxygen supersaturation in the lattice. The CO2-containing diamonds often contain micron-sized hexagonal lamellar inclusions. TEM investigation of a lamellae reveals that it consists of high quality graphite showing partial epitaxial relation with comprising diamond. The gap between the graphite and diamond may be enriched with oxygen impurity.

Global polarizations ($P$) of $\Lambda$ ($\bar{\Lambda}$) hyperons have been observed in non-central heavy-ion collisions. The strong magnetic field primarily created by the spectator protons in such collisions would split the $\Lambda$ and $\bar{\Lambda}$ global polarizations ($\Delta P = P_{\Lambda} - P_{\bar{\Lambda}} < 0$). Additionally, quantum chromodynamics (QCD) predicts topological charge fluctuations in vacuum, resulting in a chirality imbalance or parity violation in a local domain. This would give rise to an imbalance ($\Delta n = \frac{N_{\text{L}} - N_{\text{R}}}{\langle N_{\text{L}} + N_{\text{R}} \rangle} \neq 0$) between left- and right-handed $\Lambda$ ($\bar{\Lambda}$) as well as a charge separation along the magnetic field, referred to as the chiral magnetic effect (CME). This charge separation can be characterized by the parity-even azimuthal correlator ($\Delta\gamma$) and parity-odd azimuthal harmonic observable ($\Delta a_{1}$). Measurements of $\Delta P$, $\Delta\gamma$, and $\Delta a_{1}$ have not led to definitive conclusions concerning the CME or the magnetic field, and $\Delta n$ has not been measured previously. Correlations among these observables may reveal new insights. This paper reports measurements of correlation between $\Delta n$ and $\Delta a_{1}$, which is sensitive to chirality fluctuations, and correlation between $\Delta P$ and $\Delta\gamma$ sensitive to magnetic field in Au+Au collisions at 27 GeV. For both measurements, no correlations have been observed beyond statistical fluctuations., Comment: 10 pages, 10 figures; paper from the STAR Collaboration

We review the recent theoretical and observational developments concerning the interaction of the Large Magellanic Cloud (LMC) with the Milky Way and its neighbourhood. An emerging picture is that the LMC is a fairly massive companion (10-20% of the Milky Way mass) and just passed the pericentre of its orbit, likely for the first time. The gravitational perturbation caused by the LMC is manifested at different levels. The most immediate effect is the deflection of orbits of stars, stellar streams or satellite galaxies passing in the vicinity of the LMC. Less well known but equally important is the displacement (reflex motion) of central regions of the Milky Way about the centre of mass of both galaxies. Since the Milky Way is not a rigid body, this displacement varies with the distance from the LMC, and as a result, the Galaxy is deformed and its outer regions (beyond a few tens kpc) acquire a net velocity with respect to its centre. These phenomena need to be taken into account at the level of precision warranted by current and future observational data, and improvements on the modelling side are also necessary for an adequate interpretation of these data., Comment: review article (30 pages)

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Non-central collisions can produce strong magnetic fields on the order of $10^{18}$ Gauss, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and anti-quarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as $v_1(\mathsf{y})$. Here we present the charge-dependent measurements of $dv_1/d\mathsf{y}$ near midrapidities for $\pi^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ in Au+Au and isobar ($_{44}^{96}$Ru+$_{44}^{96}$Ru and $_{40}^{96}$Zr+$_{40}^{96}$Zr) collisions at $\sqrt{s_{\rm NN}}=$ 200 GeV, and in Au+Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the $v_1$ signal on collision system, particle species, and collision centrality can be qualitatively and semi-quantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the $u$ and $d$ quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations.

The polarization of $\Lambda$ and $\bar{\Lambda}$ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild $p_T$ dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and $p_T$ dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy., Comment: 6 pages, 5 figures, Published in Physical Review Letters

Thin stellar discs on both galactic and nuclear, sub-kpc scales are believed to be fragile structures that would be easily destroyed in major mergers. In turn, this makes the age-dating of their stellar populations a useful diagnostics for the assembly history of galaxies. We aim at carefully exploring the fragility of such stellar discs in intermediate- and low- mass encounters, using high-resolution N-body simulations of galaxy models with structural and kinematic properties tailored to actually observed galaxies. As a first but challenging step, we create a dynamical model of FCC 170, a nearly edge-on galaxy in the Fornax cluster with multiple galactic components and including both a galactic scale and nuclear stellar disc (NSD), using detailed kinematic data from the Multi Unit Spectroscopic Explorer and a novel method for constructing distribution function-based self-consistent galaxy models. We then create N-body realisations of this model and demonstrate that it remains in equilibrium and preserves its properties over many Gyr, when evolved with a sufficiently high particle number. However, the NSD is more prone to numerical heating, which gradually increases its thickness by up to 22 per cent in 10 Gyr even in our highest-resolution runs. Nevertheless, these N-body models can serve as realistic representations of actual galaxies in merger simulations., Comment: 13 pages, 9 figures

At very low energies, a light neutral particle above a horizontal surface can experience quantum reflection. The quantum reflection holds the particle against gravity and leads to gravitational quantum states (GQS). So far, GQS were only observed with neutrons as pioneered by Nesvizhevsky and his collaborators at ILL. However, the existence of GQS is predicted also for atoms. The GRASIAN-collaboration pursues the first observation and studies of GQS of atomic hydrogen. We propose to use atoms in order to exploit the fact that orders of magnitude larger fluxes compared to those of neutrons are available. Moreover, recently the qBounce collaboration, performing GQS spectroscopy with neutrons, reported a discrepancy between theoretical calculations and experiment which deserves further investigations. For this purpose, we set up a cryogenic hydrogen beam at 6 K. We report on our preliminary results, characterizing the hydrogen beam with pulsed laser ionization diagnostics at 243 nm.

We consider the dynamics of and emission from growing superbubbles in a stratified interstellar gaseous disc driven by energy release from supernovae explosions in stellar clusters with {masses $M_{cl}= 10^5-1.6\times 10^6~M_\odot$}. Supernovae are spread randomly within a sphere of $r_c=60$ pc, and inject energy episodically with a specific rate $1/130~M_\odot^{-1}$ proportional to the star formation rate (SFR) in the cluster. Models are run for several values of SFR in the range $0.01$ to $0.1~M_\odot$ yr$^{-1}$, with the corresponding average surface energy input rate $\sim 0.04-0.4$ erg cm$^{-2}$ s$^{-1}$. We find that the discrete energy injection by isolated SNe are more efficient in blowing superbubbles: asymptotically they reach heights of up to 3 to 16 kpc for $M_{cl}=10^5-1.6\times 10^5~M_\odot$, correspondingly, and stay filled with a hot and dilute plasma for at least 30 Myr. During this time they emit X-ray, H$\alpha$ and dust infrared emission. X-ray liminosities $L_X\propto {\rm SFR}^{3/5}$ that we derive here are consistent with observations in star-forming galaxies. Even though dust particles of small sizes $a\leq 0.03~\mu$m are sputtered in the interior of bubbles, larger grains still contribute considerably ensuring the bubble luminosity $L_{\rm IR}/{\rm SFR}\sim 5\times 10^7 L_\odot M_\odot^{-1} ~{\rm yr}$. It is shown that the origin of the North Polar Spur in the Milky Way can be connected with activity of a cluster with the stellar mass of $\sim 10^5~M_\odot$ and the ${\rm SFR}\sim 0.1~M_\odot$ yr$^{-1}$ some 25--30 Myr ago. Extended luminous haloes observed in edge-on galaxies (NGC 891 as an example) can be maintained by disc spread stellar clusters of smaller masses $M_\ast \simlt 10^5~M_\odot$., Comment: 13 pages, 18 figures, accepted to MNRAS

In a galaxy merger, the stars tidally stripped from the satellite and accreted onto the host galaxy undergo phase mixing and form finely-grained structures in the phase space. However, these fragile structures may be destroyed in the subsequent galaxy evolution, in particular, by a rotating bar that appears well after the merger is completed. In this work, we investigate the survivability of phase-space structures in the presence of a bar. We find that a bar with amplitude and pattern speed similar to those of the Milky Way would blur and destroy a substantial amount of the substructure that consists of particles with pericentre radii comparable to the bar length. While this appears to be in tension with the recent discovery of phase-space chevrons in \textit{Gaia} DR3 data, the most prominent chevrons in our simulations can still be recovered when applying the same analysis procedure as in observations. Moreover, the smoothing effect is less pronounced in the population of stars whose angular momenta have the opposite sign to the bar pattern speed., Comment: 5 pages, 7 figures, accepted by MNRAS

Point-particle dynamics is reformulated as a field theory. This is achieved by using the unfolded dynamics approach that makes it possible to give dynamical interpretation to the concept of physical dimension which is 1 for a point particle in the $d$-dimensional space-time. The main idea for the description of a $k$-dimensional on-shell system in the $d$-dimensional space is to keep the evolution along $d-k$ dimensions off-shell or, alternatively, restrict it in a specific way respecting the compatibility conditions of the resulting unfolded system. The developed approach gives some hints how a non-linear realization of the symmetry $G$ of a larger-dimensional space in a lower-dimensional system can emerge from a geometrical realization on the fields in an appropriate $G$-invariant space. For the example of a relativistic point particle considered in this paper, $ G$ is the Poincare group. The proposed general scheme is illustrated by simple examples that reproduce conventional results., Comment: 16 pages