We investigate the spatially-resolved dynamics of the collective amplitude Schmid-Higgs (SH) mode in disordered s-wave superconductors and fermionic superfluids. By analyzing the analytic structure of the zero-temperature SH susceptibility in the complex frequency plane, we find that when the coherence length greatly exceeds the mean free path: (i) the SH response at fixed wave vectors exhibits late-time oscillations decaying as 1/t2 with frequency 2Δ, where Δ is the superconducting gap; (ii) sub-diffusive oscillations with a dynamical exponent z=4 emerge at late times and large distances; and (iii) spatial oscillations at fixed frequency decay exponentially, with a period that diverges as the frequency approaches 2Δ from above. When the coherence length is comparable to the mean free path, additional exponentially-decaying oscillations at fixed wave vectors appear with frequency above 2Δ. Furthermore, we show that the SH mode induces an extra peak in the third-harmonic generation current at finite wave-vectors. The frequency of this peak is shifted from the conventional resonance at Δ, thereby providing an unambiguous signature of order parameter amplitude dynamics.

Optimization of the mean completion time of random processes by restart is a subject of active theoretical research in statistical physics and has long found practical application in computer science. Meanwhile, one of the key issues remains largely unsolved: how to construct a restart strategy for a process whose detailed statistics are unknown to ensure that the expected completion time will reduce? Addressing this query here we propose several constructive criteria for the effectiveness of various protocols of non-instantaneous restart in the mean completion time problem and in the success probability problem. Being expressed in terms of a small number of easily estimated statistical characteristics of the original process (MAD, median completion time, low-order statistical moments of completion time), these criteria allow informed restart decision based on partial information.

Both Markovian and arbitrary residence time distributions are considered. The comparison of analytical predictions with the case of a time-decorrelated process shows that correlations can both decrease and increase the corresponding expected waiting time. Besides, the comparison of exponential, subexponential, and heavy-tailed models characterized by equal probabilities to observe the event of interest demonstrates that a faster decrease in the residence time probability density implies a shorter expected waiting time. Interestingly, irrespective of the details of a particular model for both discrete- and continuous-time jump processes considered here, the random waiting time becomes exponentially distributed in the long-time limit, thus, showing remarkable universality.

Изучается зеркальная симметрия многообразий Калаби-Яу, построение моделей N=2 суперконформной теории поля, необходимых для суперструны, а также вычисление специальной Кэлеровой геометрии на пространстве модулей Калаби-Яу при помощи некоторой дуальности с калибровочными линейными сигма моделями.
Доказана эквивалентность конструкций зеркальной симметрии Батырева и Берглунда-Хубша-Кравица для орбифолдов Калаби-Яу, заданных нулями полинома во взвешенном проективном пространстве. Получены уравнения определяющие мономы-деформации зеркального полинома. Рассмотрены зеркальные пары орбифолдов квинтики.
Установлена дуальная калибровочная линейная сигма модель (GLSM) для Калаби-Яу типа Берглунда-Хубша. В рамках этой дуальности проверена так называемая зеркальная версия гипотезы Джокерса о равенстве экспоненты Кэлерова потенциала на пространстве модулей Калаби-Яу и статсуммы GLSM.
Построены N=2 суперконформные теории поля с центральным зарядом равным 9. Левые и правые примарные поля в этих теориях связаны согласно A-D-E классификации модулярно-инвариантных статсумм. Рассмотренны орбифолды произведений минимальных моделей соответствующие многообразиям Калаби-Яу типа Ферма. Получены уравнения взаимной локальности твистованных полей.

Модели Гетеротических струны в 4-х измерениях, полученные ранее Гепнером, представляют собой гибридные теории. В левом секторе этих теорий исходно имеется 10-мерная N=1 Суперконформная теория поля, дополнительные к четырем 6 измерений которой компактифицированы на произведение N=2 минимальных моделей. В правом секторе есть 26-мерная бозонная струна, 6 измерений которой также компактифицированы на произведения N=2 Минимальных моделей, а остальные 13 измерений компактифицированы на тор алгебры Ли E(8)xSO(10). Будет показано, как использовать аксиомы Конформного бутстрапа, включая требование взаимной локальности полей, для построения таких моделей в общем случае. А именно, будет показано, что модели, построенные из требований одновременного выполнения взаимной локальности левых вертексов с генераторами N=1 Пространственно-Временной Суперсимметрии, и выполнение взаимной локальности правых вертексов с генераторами Калибровочной симметрии, а также из дополнительного требования взаимной локальности левых-правых вершин между собой, следует, что такие модели, чтобы быть самосогласованными, обязательно должны обладать калибровочной симметрией, алгебра Ли которой есть E(8)xE(6). Как известно, наличие N=1 Суперсимметрии Пространства-Времени, а также E(8)xE(6) Калибровочной симметрии является необходимым из феноменологических соображений. Рассмотренный ранее класс моделей Гетеротической струнны ограничен тем, что компактификация 6 из 10 измерений пространства-времени в их конструкциях в основном осуществляется на многообразиях Калаби-Яу, соответствующих произведениям $N=2$ Минимальных моделей. Такие многообразия представляют собой специальный подкласс многообразий Калаби-Яу типа Берглунда-Хубша. Будет показано, как, используя подходы Фейгина-Фукса и Батырева-Борисова, распространить нашу конструкцию на общий случай на многообразий Калаби-Яу этого типа.

In recent literature there is an active discussion on well-posedness of description of waves' interaction by a kinetic equation for different models. In this work kinetic equation for capillary waves on a surface of the fluid is considered. While it is clear, that proof of well-posedness of a problem through numerical experiment is impossible, results of a series of numerical experiments, similar to ones from a recent work arXiv:2109.02477 (Phys. Rev. Lett., vol. 129, p. 034101 (2022)) are considered. It is shown, that if one takes into account scaling with respect to parameters of a kinetic equation, results coincide. It means, that a least in the range of parameters used for experiments, kinetic equation qualitatively, though most probably qualitatively as well, describes interaction of capillary waves.

The population-averaged contact maps generated by the chromosome conformation capture technique provide important information about the average frequency of contact between pairs of chromatin loci as a function of the genetic distance between them. However, these datasets do not tell us anything about the joint statistics of simultaneous contacts between genomic loci in individual cells. This kind of statistical information can be extracted using the single-cell Hi-C method, which is capable of detecting a large fraction of simultaneous contacts within a single cell, as well as through modern methods of fluorescent labeling and super-resolution imaging. Motivated by the prospect of the imminent availability of relevant experimental data, in this work, we theoretically model the joint statistics of pairs of contacts located along a line perpendicular to the main diagonal of the single-cell contact map. The analysis is performed within the framework of an ideal polymer model with quenched disorder of random loops, which, as previous studies have shown, allows us to take into account the influence of the loop extrusion process on the conformational properties of interphase chromatin.

Recently, there has been renewed interest in studies of criticality in the spin quantum Hall ef- fect, realized in the Altland-Zirnbauer symmetry class C of disordered, noninteracting fermions in two spatial dimensions. In our study, we develop a nonperturbative analysis of the replica two- dimensional nonlinear sigma model in class C. We explicitly construct the instanton solution with a unit topological charge. By treating fluctuations around the instanton at the Gaussian level, we calculate the instanton correction to the disorder-averaged logarithm of the partition function. We compute non-perturbative corrections to the anomalous dimensions of pure power-law scaling local operators, which determine the spectrum of generalized multifractality. We also calculate instanton corrections to the renormalized longitudinal and Hall spin conductivities and determine the topol- ogy of the phase diagram for class C. Our results demonstrate that the spin quantum Hall effect is indeed a close cousin of the integer quantum Hall effect. In this talk the crossover between class A and class C will be described.

We analyze the effect of the parton color randomization on p_T broadening in the quark-gluon plasma with turbulent color fields. We calculate the transport coefficient qhat for a simplified model of fluctuating color fields in the form of alternating sequential transverse layers with homogenous transverse chromomagnetic fields with random orientation in the SU(3) group and gaussian distribution in the magnitude. Our numerical results show that the color randomization can lead to a sizable reduction of the turbulent contribution to qhat. The magnitude of the effect grows with increasing ratio of the electric and magnetic screening masses.

We calculate the medium modification factor I_pA for 5.02 TeV p+Pb collisions. We use the Monte-Carlo Glauber model to determine the parameters of the quark-gluon plasma fireball in pA jet events. Our calculations show that the jet quenching effect for I_pA turns out to be rather small. We have found that the theoretical I_pA as a function of the underlying event charged multiplicity density, within errors, agrees with data from ALICE for 5.02 TeV p+Pb collisions. However, the experimental errors are too large to draw a firm conclusion on the possible presence of jet quenching.

A theoretical description of altermagnets in the normal and superconducting states is presented. It was made in comparison with metals that do not have spatial inversion symmetry. Having a formally similar mathematical description, these two classes of metals have qualitatively different physical properties.
Submitted to JETP Letters.

We study the scattering of edge states of 2D topological insulator in the uniform external magnetic field due to edge imperfections, common in realistic 2D topological insulator samples. The external magnetic field breaks time-reversal symmetry, opening the possibility of the scattering of otherwise topologically protected fermionic edge states. The scattering happens to be always an over-barrier event, irrespective of the shape of the edge deformation and magnitude of the magnetic field. We use the advanced Pokrovsky–Khalatnikov semiclassical approach, which allows us to obtain analytically both the main exponential and pre-exponential factors of the scattering amplitude for wide classes of analytic deformation profiles.

Magnetic quantum oscillations (MQO) provide a common tool to probe the electronic structure of various conductors. The Fermi surface of most metals is now known due to the MQO. This tool is more precise than its alternatives, but requires low temperatures, clean samples and rather strong magnetic fields. In this paper the MQO of Hall coefficient are measured in rare-earth tritelluride TmTe3 and shown to be much stronger and persist to higher temperature than the Shubnikov-de Haas oscillations. This amplitude enhancement simplifies the MQO experiments and is very general in strongly anisotropic metals. The combined measurements of Hall and diagonal magnetoresistance provide additional useful information. The ratio of their MQO amplitudes depends linearly on magnetic field, and its slope gives a simple and accurate measurement tool of the electron mean free time and its temperature dependence, unachievable from the usual Dingle plot. Our results expand the use and applications of MQO as a powerful tool to investigate the electronic structure.

Modeling the motion of ultracold neutrons (UCN) is important for estimating their losses, accurately measuring their lifetime, and describing other experiments. In material traps, it is necessary to take into account not only specular but also diffuse elastic reflection of UCN from the trap walls. Usually, such diffuse scattering is described using Lambert's cosine law for the angular distribution of scattered neutrons, which does not have a strict theoretical derivation and is often violated. In our work, we propose an experiment that allows measuring the deviation of the angular distribution of UCN during diffuse scattering from the Lambert law. This deviation can be determined by the difference in the number of neutrons emitted through the central and end windows of a long narrow UCN trap. Monte Carlo calculations were performed that correspond to a possible experiment and show a significant effect for different trap shapes. Other issues related to UCN losses during interaction with the walls of material traps were also investigated.

The quasi-two-dimensional organic metal κ-(BEDT-TTF)2Hg(SCN)2Cl upon cooling below T = 30 K passes into the Mott insulator state. External hydrostatic pressure P > 0.7 kbar restores the metallic state and makes it possible to study the behavior of resistance, magnetoresistance and Shubnikov-de Haas oscillations at helium temperatures in the range of external pressures P = 1-8 kbar. The spectrum of the observed Shubnikov-de Haas oscillations agrees well with theoretical calculations of the band structure. At the same time, the oscillation characteristics (cyclotron mass, frequency, amplitude) are significantly affected by electron correlations. Strongly correlated systems also have a specific temperature dependence of resistance. In this case, pressure is the main tool controlling the strength of correlations. Various versions of the influence of pressure on the behavior of the non-oscillating part of magnetoresistance are discussed.

We study the magnon spectrum in a thin ferromagnetic-superconductor heterostructure in the presence of a single superconducting vortex. We employ the Bogolubov-de Gennes Hamiltonian which describes the magnons in the presence of the stray magnetic field and the non-uniform magnetic texture induced by the vortex. We find that the vortex localizes magnon states approximately in the same way as a charge center produces electron bound states due to screened Coulomb interaction in the two-dimensional electron gas. The number of these localized states is substantially determined by the material parameters of the ferromagnetic film only. We solve the scattering problem for an incident plane spin wave and compute the total and transport cross sections. We demonstrate that the vortex-induced non-uniform magnetic texture in chiral ferromagnetic film produces a skew scattering of magnons. We explore the peculiarities of the quantum scattering problem that correspond to orbiting in the classical limit.
Results are published in D.S. Katkov, S.S. Apostoloff, I. S. Burmistrov, ``Bound states and scattering of magnons on a superconducting vortex in ferromagnet-superconductor heterostructures’’, Pis'ma v ZhETF 120, 681 (2024) .(http://jetpletters.ru/ps/2486/article_36479.pdf)