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A comprehensive diagnostics of new-generation dispersive elements based on Bragg structures was completed. The influence of inscription parameters on the properties of samples was studied and a threshold inscription intensity of ~ 6.38 TW/cm2 at which the linear absorption coefficient as well as the phase and polarization stresses sharply increase was found. When inscription is made with an average intensity below the threshold, the linear absorption in dry silica samples remains at a level of 10-5 cm-1, which is approximately two orders of magnitude lower than that of currently available commercial samples. The measured values of the dispersion characteristics using a white light interferometer coincided are in a good agreement with the calculated values provided by the manufacturer. The results of the diagnostics show that the new-generation dispersive elements are promising for compressing kilowatt-level radiation of average power., Comment: 9 pages, 8 figures

The low-frequency variability of the mid-latitude atmosphere involves complex nonlinear and chaotic dynamical processes posing predictability challenges. It is characterized by sporadically recurring, often long-lived patterns of atmospheric circulation of hemispheric scale known as weather regimes. The evolution of these circulation regimes in addition to their link to large-scale teleconnections can help extend the limits of atmospheric predictability. They also play a key role in sub- and inter-seasonal weather forecasting. Their identification and modeling remains an issue, however, due to their intricacy, including a clear conceptual picture. In recent years, the concept of metastability has been developed to explain regimes formation. This suggests an interpretation of circulation regimes as communities of states in which the atmospheric system remains in their neighborhood for abnormally longer than typical baroclinic timescales. Here we develop a new and effective method to identify such communities by constructing and analyzing an operator of the system's evolution via hidden Markov model (HMM). The method makes use of graph theory and is based on probabilistic approach to partition the HMM transition matrix into weakly interacting blocks -- communities of hidden states -- associated with regimes. The approach involves nonlinear kernel principal component mapping to consistently embed the system state space for HMM building. Application to northern winter hemisphere using geopotential heights from reanalysis yields four persistent and recurrent circulation regimes. Statistical and dynamical characteristics of these circulation regimes and surface impacts are discussed. In particular, unexpected high correlations are obtained with EL-Nino Southern Oscillation and Pacific decadal oscillation with lead times of up to one year., Comment: 17 pages, 6 figures

Experimental data and results of numerical simulations are presented, concerning excitation of narrowband gigahertz-range wave trains in coaxial guiding structures that are partially filled with ferromagnetic material and may involve periodically arranged metal inserts. The experiments performed confirm the possibility of exciting weakly damped electromagnetic waves by feeding high voltage, unilateral electromagnetic pulses of short duration into the line. The coax line was of outer diameter 50.5 mm, filled with an isotropic dielectric (relative dielectric constant {\epsilon} = 2.25) and a set of ferrite rings with {\epsilon}=16 and saturated-state {\mu} about 4 to 5. With a peak voltage of the primary pulse close to 160 kV and a magnetizing field of 17.5 kA/m, the parameters of the waves excited reached magnitudes as: frequency 1.89 GHz to 2.1 GHz; bandwidth 16%; VHF power at the output about 20 MW., Comment: 4 pages, 10 figures

Results of research are presented concerning operative modes of a high-voltage (relativistic) pulsed magnetron for the 8 mm wavelength range. Technical solutions are proposed for improving the output system of the device, such as to increase the efficiency of power extraction from the field-particle interaction space. The stability of the magnetron operation has been increased, enhanced quantitative indices of the output power to 381 kW in each of the two linear polarizations. And a stabilized frequency spectrum from 35.7 to 40 GHz of the EHF radiation generated., Comment: 4 pages, 6 figures

We consider a spin valve composed of a superconducting film (S) between two ferromagnetic insulators (FI) on two sides. In the dirty limit the superconductor is described by Usadel equations. Appropriate boundary conditions were chosen for two S-FI interfaces, which are described via the interface parameter spin mixing angle. By numerically solving the Usadel equations, the density of states (DOS) at different spin mixing angles were obtained. It was shown previously that critical temperature of such FI-S-FI structure depends on the mutual alignment of the FI layers magnetization. We follow the evolution of DOS at change of misalignment of ferromagnets magnetization and probe the zero bias peak creation. The DOS characteristic features may give a fruitful information about triplet superconducting components creation and interplay inside the S layer.

Magnetic field-induced electric polarization has been observed in trigonal non-centrosymmetric paramagnetic Pr3Ga5SiO14 langasite. We detected quadratic electric polarization along the a-axis in the basal ab plane for various magnetic-field orientations. Electric polarization along the c-axis is only evident starting from the fourth power of magnetic field, in accordance with the trigonal symmetry. The magnetic properties of Pr3Ga5SiO14 primarily stem from the local anisotropic magnetic moment of the two lowest Pr3+ singlets (quasi-doublet) in the crystal electric field. The random distribution of Ga/Si in the 2d positions leads to a local distortion of C2 symmetry and to a splitting distribution of the quasi-doublet. By considering the interactions of local moments among different Pr3+ positions within a phenomenological approach for the allowed magnetoelectric coupling, we derive the electric polarization in terms of symmetry-allowed combinations of local magnetic susceptibilities and field components. The magnetic field dependence of electric polarization in the basal plane, P_{a,b*}, is mainly determined by the accumulation of effective local susceptibilities, exhibiting similar behavior in low fields, while polarization along the c-axis, P_c, arises from the non-equivalence of local effective magnetic susceptibilities in different Pr3+ positions. Our findings suggest that the temperature dependencies of magnetic and magnetoelectric susceptibilities are highly sensitive to the distribution of the quasi-doublet splitting, which reflects the local symmetry breaking.

In this work, we studied X-ray source SRGe~J021932.4$-$040154 (SRGe J021932), which we associated with a single X-ray active star of spectral class G2V-G4V and the rotational period $\rm P_{rot} < 9.3$ days. Additional analysis of TESS light-curves allowed for the rotational period estimation of $3.2 \pm 0.5$ days. SRGe J021932 was observed with the SRG/eROSITA during eUDS survey in 2019 in a much dimmer state compared to the XMM-Newton catalogue 4XMM-DR12. Detailed analysis revealed that the archival XMM-Newton observations captured the source during a flaring event in 2017. The XMM-Newton light curve demonstrates a strong flare described with the Gaussian rise and exponential decay, typical for stellar flares, characterized by timescales of ${\sim}400$~s and ${\sim}1300$~s, respectively. The spectral analysis of the quiescent state reveals ${\sim}10$~MK plasma at luminosity of $(1.4\pm0.4) \times 10^{29}$ erg/s (0.3-4.5 keV). The spectrum of the flare is characterized by temperature of ${\sim}40$ MK and luminosity $(5.5\pm0.6)\times 10^{30}$ erg/s. The total energy emitted during the flare ${\sim}1.7 \times 10^{34}$ erg exceeds the canonical threshold of $10^{33}$ erg, allowing us to classify the observed event as a superflare on a rapidly-rotating solar-type star. Additionally, we present the upper limit on the surface starspot area based on the brightness variations and consider the hypothesis of the object being a binary system with G-type and M-type stars, suggested by two independent estimations of radial velocity variations from APOGEE-2 and Gaia., Comment: Published in Journal of High Energy Astrophysics

An analytically solvable model of unsaturated lipid bilayer is derived by introducing finite bending angle of the unsaturated bond relative to straight part of the lipid chain considered previously in our model of semi-flexible strings. It is found that lateral pressure profile of unsaturated lipids has distinct maximum in the unsaturated bond region due to enhanced excluded volume effect caused by the bent bond, leading to an increase of entropic repulsion between the lipid chains. Simultaneously, just away from the unsaturated bond some parts of the neighbouring lipid chains have less probability to collide by geometrical reasons, causing depletion of entropic repulsion relative to saturated lipid chains case and resulting in the local minima of the lateral pressure profile surrounding the maximum at the bent unsaturated bond. Lipid chain order parameter, lateral pressure profile, and area per lipid are computed for POPC and compared with those for DPPC lipid bilayer.

The magnetic properties of Ho-doped langasites (La:Ho)$_3$Ga$_5$SiO$_{14}$ are dominated by the Ising-like magnetic moments of the Ho$^{3+}$ ions. In their saturated regime, the induced magnetic state breaks both time and space inversion symmetries, leading to a novel linear magnetoelectric effect. However, due to distortions induced by a shared Ga/Si occupancy of the 2d sites, resolving the microscopic nature of the magnetic configuration remains a difficult task. Here we combine polarized neutron diffraction and angular dependent magnetization experiments to determine the local distortions of the Ho$^{3+}$ magnetic moments in doped langasites (La$_{1-x}$Ho$_x$)$_3$Ga$_5$SiO$_{14}$ with $x \approx 0.015$ and $x \approx 0.045$. We propose a model for a field-induced magnetic configuration with arbitrary orientations of the local Ising axis of Ho$^{3+}$ in distorted positions. The operations of broken local $C_2$ symmetry and rotations around the trigonal $C_3$ axis connect different sites, restoring the global P321 symmetry of the crystal and simplifying the description of the magnetic properties. The superposition of two distorted Ho$^{3+}$ positions connected by $C_2$ symmetry determines the local magnetic susceptibility tensor, which no longer appears Ising-like at low fields.

We propose a conjectural correspondence between the spectra of the Bethe algebra for the quantum toroidal $\mathfrak{gl}_2$ algebra on relaxed Verma modules, and $q$-hypergeometric opers with apparent singularities. We introduce alongside the notion of apparent singularities for linear $q$-difference operators and discuss some of their properties. We also touch on a generalization to $\mathfrak{gl}_n$., Comment: Latex, 30 pages

Using tremendous photon statistics gained with the stray light aperture of the NuSTAR telescope over 11 years of operation, we set strong limits on the emission of close to monochromatic photons from the radiative decays of putative dark matter sterile neutrinos in the Milky Way. In the energy range of 3-20 keV covered by the NuSTAR, the obtained limits reach the bottom edge of theoretical predictions of realistic models where sterile neutrinos are produced in the early Universe. Only a small region is left to explore, if the sterile neutrinos form the entire dark matter component., Comment: 11 pages, 11 figures, accepted by Phys. Rev. Lett

A quasi-exponential is an entire function of the form $e^{cu}p(u)$, where $p(u)$ is a polynomial and $c \in \mathbb{C}$. Let $V = \langle e^{h_1u}p_1(u), \dots, e^{h_Nu}p_N(u) \rangle$ be a vector space with a basis of quasi-exponentials. We show that if $h_1, \dots, h_N$ are nonnegative and all of the complex zeros of the Wronskian $\operatorname{Wr}(V)$ are real, then $V$ is totally nonnegative in the sense that all of its Grassmann-Pl\"{u}cker coordinates defined by the Taylor expansion about $u=t$ are nonnegative, for any real $t$ greater than all of the zeros of $\operatorname{Wr}(V)$. Our proof proceeds by showing that the higher Gaudin Hamiltonians $T_\lambda^G(t)$ introduced in [ALTZ14] are universal Pl\"ucker coordinates about $u=t$ for the Wronski map on spaces of quasi-exponentials. The result that $V$ is totally nonnegative follows from the fact that $T_\lambda^G(t)$ is positive semidefinite, which we establish using partial traces. We also show that if $h_1 = \cdots = h_N = 0$ then $T_\lambda^G(t)$ equals $\beta^\lambda(t)$, which is the universal Pl\"ucker coordinate for the Wronski map on spaces of polynomials introduced in [KP23]., Comment: 24 pages

Flexible transparent electrodes, encompassing the combination of optical transparency and electrical conductivity, empower numerous optoelectronic applications. While the main efforts nowadays concentrate on developing wire meshes and conductive oxides, those technologies are still in a quest to find a balance between price, performance, and versatility. Here we propose a new platform, encompassing the advantages of nanophotonic design and roll-to-roll large-scale lithography fabrication tools, granting an ultimate balance between optical, electrical, and mechanical properties. The design is based on an array of silica microspheres deposited on a patterned thin aluminum film attached to a flexible polymer matrix. Microspheres are designed to squeeze 80% light through nanoscale apertures with the aid of the photonic nanojet effect given the light impinges the structure from the top. The photonic structure blocks the transmission for the backpropagation direction thus granting the device with the high 5-fold level of asymmetry. The patterned layer demonstrates a remarkable 2.8 {\Omega}/sq sheet resistance comparable to that of a continuous metal layer. The high conductivity is shown to be maintained after a repeatable application of strain on the flexible electrode. The technical specifications of the demonstrated transparent electrode establish it as a viable option for integrating into advanced optoelectronic devices such as solar cells, touchscreens, and organic light-emitting diodes to name a few. Its notable capacity to optimize light transmittance while ensuring consistent electrical performance, alongside its mechanical flexibility, makes the demonstrated device an essential component for applications, where such attributes are critically required., Comment: 16 pages, 5 pages, 1 table

We show that many tame modules of the quantum toroidal $\mathfrak{gl}_2$ algebra can be explicitly constructed in a purely combinatorial way using the theory of $q$-characters. The examples include families of evaluation modules obtained from analytic continuation and automorphism twists of Verma modules of the quantum affine $\mathfrak{gl}_2$ algebra. The combinatorial bases in the modules are labeled by colored plane partitions with various properties., Comment: Latex, 26 pages, 12 figures

The polynomial ideals studied by A. Garsia and C. Procesi play an important role in the theory of Kostka polynomials. We give multiparameter flat deformations of these ideals and define an action of the extended affine symmetric group on the corresponding quotient algebras multiplied by the sign representation. We show that the images of these modules under the affine Schur-Weyl duality are dual to the local Weyl modules for the loop algebra $\mathfrak{sl}_{n+1}[t^{\pm 1}].$, Comment: Latex, 24 pages

Efficient doping of semiconductor nanowires remains a major challenge towards the commercialization of nanowire-based devices. In this work we investigate the growth regimes and electrical properties of MBE-grown p- and n-type gallium phosphide nanowires doped with Be and Si respectively. Electrical conductivity of individual nanowires is quantitatively studied via atomic force microscopy supported with numerical analysis. Based on conductivity measurements, we provide growth strategies for achieving the doping level up to 5E18 and 2E19 $cm^{-3}$ for GaP:Si and GaP:Be nanowires respectively, which is high enough to be demanded for technological applications.

The low frequency variability of the extratropical atmosphere involves hemispheric-scale recurring, often persistent, states known as teleconnection patterns or regimes, which can have profound impact on predictability on intra-seasonal and longer timescales. However, reliable data-driven identification and dynamical representation of such states are still challenging problems in modeling dynamics of the atmosphere. We present a new method, which allows both to detect recurring regimes of atmospheric variability, and to obtain dynamical variables serving as an embedding for these regimes. The method combines two approaches from nonlinear data analysis: partitioning a network of recurrent states with studying its properties by the recurrence quantification analysis and the kernel principal component analysis. We apply the method to study teleconnection patterns in a quasi-geostrophical model of atmospheric circulation over the extratropical hemisphere as well as to reanalysis data of geopotential height anomalies in the mid-latitudes of the Northern Hemisphere atmosphere in the winter seasons from 1981 to the present. It is shown that the detected regimes as well as the obtained set of dynamical variables explain large-scale weather patterns, which are associated, in particular, with severe winters over Eurasia and North America. The method presented opens prospects for improving empirical modeling and long-term forecasting of large-scale atmospheric circulation regimes., Comment: 20 pages, 14+3 figures

We consider the Schr\"odinger operators which are constructed from the $\lambda$-opers corresponding to solutions of the $\widehat{\mathfrak{sl}}_2$ Gaudin Bethe Ansatz equations. We define and study the connection coefficients called the $Q$-functions. We conjecture that the $Q$-functions obtained from the $\lambda$-opers coincide with the $Q$-functions of the Bazhanov-Lukyanov-Zamolodchikov opers with the monster potential related to the quantum KdV flows. We give supporting evidence for this conjecture., Comment: Revised version, new section about the action of the reproduction procedures on opers and Q functions. 1 figure

The paper is devoted to the Thomson scattering (TS) diagnostics recently developed for the Globus-M2 spherical tokamak and prototyping the ITER divertor TS diagnostics. The distinctive features of the system are the use of spectrometers, acquisition system and lasers that meet the base requirements for ITER TS diagnostics. The paper describes the diagnostic system that allows precise measurements of TS signals, as well as the results of the first measurements of electron temperature and density in both central region of the plasma column and scrape-off layer. The system provides measurements of electron temperature $T_{e}$ in the range of 5 eV to 5 keV and density $n_{e}$ in the range of $5{\cdot}10^{17}{\div}3.25{\cdot}10^{20} m^{-3}$. The use of two ITER-grade probing lasers of different wavelengths (Nd:YAG 1064.5 nm and Nd:YLF 1047.3 nm) allows reliable measurement of $T_{e}$ in multi-colour mode, i.e., assuming that spectral calibration is unknown.

The large side aperture of the NuSTAR telescope for unfocused photons (so-called stray light) is a known source of rich astrophysical information. To support many studies based on the NuSTAR stray light data, we present a fully automatic method for determining detector area suitable for background analysis and free from any kind of focused X-ray flux. The method's main idea is `a trous' wavelet image decomposition, capable of detecting structures of any spatial scale and shape, which makes the method of general use. Applied to the NuSTAR data, the method provides a detector image region with the highest possible statistical quality, suitable for the NuSTAR stray light studies. We developed an open-source Python nuwavdet package, which implements the presented method. The package contains subroutines to generate detector image region for further stray light analysis and/or to produce a list of detector bad-flagged pixels for processing in the NuSTAR Data Analysis Software for conventional X-ray analysis., Comment: 9 pages, 10 figures. Published in Journal of Astronomical Telescopes, Instruments, and Systems (JATIS)

Quantum batteries, which are quantum systems to be used for storage and transformation of energy, are attracting research interest recently. A promising candidate for their investigation is the Dicke model, which describes an ensemble of two--level systems interacting with a single--mode electromagnetic wave in a resonator cavity. In order to charge the battery, a coupling between the ensemble of two--level systems and resonator cavity should be turned off at a certain moment of time. This moment of time is chosen in such a way, that the energy gets fully stored in the ensemble of two--level systems. In our previous works we have investigated a ``bound luminosity'' superradiant state of the extended Dicke model and found analytical expressions for dynamics of coherent energy transfer between superradiant condensate and the ensemble of the two--level systems. Here, using our previous results, we have derived analytically the superlinear law for the quantum battery charging power $P\sim N^{3/2}$ as function of the number $N$ of the two--level systems in the battery, and also $N$-dependence for the charging time $t_c\sim N^{-1/2}$. The $N$--exponent $3/2$ of the charging power is in quantitative correspondence with the recent result ${1.541}$ obtained numerically by other authors. The physics of the Dicke quantum battery charging is considered in detail.

Analytic solution of semiclassical dynamics equations of the Dicke model in a superradiant state is presented. The time dependences of the amplitudes of superradiant bosonic condensate and coherent two-level atomic array in the microwave cavity prove to be expressed via Jacobi elliptic functions of real time and manifest existence of an adiabatic invariant of motion in the strongly coupled system. The periodic beatings of the photonic and atomic coherent state amplitudes are shifted in time revealing an effect of 'bound luminosity', when energy stored in the two-level system during 'darkness' in the cavity is suddenly converted into photonic condensate that 'illuminates' the cavity for half a period, before it plunges into 'darkness' again.

When estimating target parameters in nonparametric models with nuisance parameters, substituting the unknown nuisances with nonparametric estimators can introduce ``plug-in bias.'' Traditional methods addressing this suboptimal bias-variance trade-off rely on the \emph{influence function} (IF) of the target parameter. When estimating multiple target parameters, these methods require debiasing the nuisance parameter multiple times using the corresponding IFs, which poses analytical and computational challenges. In this work, we leverage the \emph{targeted maximum likelihood estimation} (TMLE) framework to propose a novel method named \emph{kernel debiased plug-in estimation} (KDPE). KDPE refines an initial estimate through regularized likelihood maximization steps, employing a nonparametric model based on \emph{reproducing kernel Hilbert spaces}. We show that KDPE: (i) simultaneously debiases \emph{all} pathwise differentiable target parameters that satisfy our regularity conditions, (ii) does not require the IF for implementation, and (iii) remains computationally tractable. We numerically illustrate the use of KDPE and validate our theoretical results., Comment: To appear at the Forty-first International Conference on Machine Learning (ICML 2024)

We define and study the shuffle algebra $Sh_{m|n}$ of the quantum toroidal algebra $\mathcal E_{m|n}$ associated to Lie superalgebra $\mathfrak{gl}_{m|n}$. We show that $Sh_{m|n}$ contains a family of commutative subalgebras $\mathcal B_{m|n}(s)$ depending on parameters $s=(s_1,\dots,s_{m+n})$, $\prod_i s_i=1$, given by appropriate regularity conditions. We show that $\mathcal B_{m|n}(s)$ is a free polynomial algebra and give explicit generators which conjecturally correspond to the traces of the $s$-weighted $R$-matrix computed on the degree zero part of $\mathcal E_{m|n}$ modules of levels $\pm 1$., Comment: Latex 31 page

Proposed by the author Q-ball mechanism of the pseudogap state and high-Tc superconductivity in cuprates was recently supported by micro X-ray diffraction data in HgBa$_2$CuO$_{4+y}$. This provides a remarkable opportunity to investigate X-ray diffraction produced by the quantum thermodynamic time crystals, a direct embodiment of those are just the Euclidean Q-balls considered in the aforementioned theory. Simultaneously, it is also demonstrated that T-linear temperature dependence of electrical resistivity in the Q-ball phase arises due to scattering of electrons on the condensed charge/spin fluctuations inside the Q-balls. This gives a clue concerning possible mechanism of T-linear behaviour of electrical resistivity in the strange metal phase of high-T$_c$ cuprates. For this purpose the Green's functions of X-ray photons and fermions scattered by the Q-balls in the pseudogap phase of high-Tc superconductors are calculated using the Feynman diagrammatic technique. The Bragg's peaks intensity, provided by the imaginary part of the retarded photon Green's function, is calculated. In total, obtained results describe X-ray and electron scattering on the finite size Q-ball of CDW/SDW density, that oscillates with bosonic frequency $\Omega=2\pi nT$ in Matsubara time, i.e. the quantum thermodynamic time crystal. It is found, that theoretical results are in good correspondence with X-ray diffraction data in HgBa$_2$CuO$_{4+y}$ reported recently. The T-linear dependence of electrical resistivity arises due to inverse temperature dependence of the Q-ball radius as function of temperature., Comment: 21 pages, 9 figures

Local deformation of atomically thin van der Waals materials provides a powerful approach to create site-controlled chip-compatible single-photon emitters (SPEs). However, the microscopic mechanisms underlying the formation of such strain-induced SPEs are still not fully clear, which hinders further efforts in their deterministic integration with nanophotonic structures for developing practical on-chip sources of quantum light. Here we investigate SPEs with single-photon purity up to 98% created in monolayer WSe$_2$ via nanoindentation. Using photoluminescence imaging in combination with atomic force microscopy, we locate single-photon emitting sites on a deep sub-wavelength spatial scale and reconstruct the details of the surrounding local strain potential. The obtained results suggest that the origin of the observed single-photon emission is likely related to strain-induced spectral shift of dark excitonic states and their hybridization with localized states of individual defects., Comment: 8 pages, 4 figures