Bistability and Hysteresis of Intersubband Absorption in Strongly Interacting Electrons on Liquid Helium

We study nonlinear inter-subband microwave absorption of electrons bound to the liquid helium surface. Already for a comparatively low radiation intensity, resonant absorption due to transitions between the two lowest subbands is accompanied by electron overheating. The overheating results in a significant population of higher subbands. The Coulomb interaction between electrons causes a shift of the resonant frequency, which depends on the population of the excited states and thus on the electron temperature $T_e$. The latter is determined experimentally from the electron photoconductivity. The experimentally established relationship between the frequency shift and $T_e$ is in reasonable agreement with the theory. The dependence of the shift on the radiation intensity introduces nonlinearity into the rate of the inter-subband absorption resulting in bistability and hysteresis of the resonant response. The hysteresis of the response explains the behavior in the regime of frequency modulation, which we observe for electrons on liquid $^3$He and which was previously seen for electrons on liquid $^4$He

Climate variations in the Northern Hemisphere based on the use of an atmosphere-ocean IPCC model

Forced and natural variability of modelled and observed Atlantic Ocean temperature and Atlantic Meridional Overturning Circulation (AMOC) is studied. In the observations and in a forced climate model run, we find increasing temperature at 1000m in the Atlantic (20N). SVD analysis shows that, for both model data and observations, a high index of North Atlantic Oscillation (NAO) corresponds to negative temperature anomaly at 1000m to the north of 55N, although geographical details of temperature anomaly distribution are different for the model and observations. Particular attention has been paid to the influence of the fresh water flux due to the present global warning on the slowing down of the AMOC. It is shown that fresh water flux change is only a secondary cause of reduced AMOC in global warming conditions, while heat flux change is probably the main reason. Finally, it is shown that internal model AMOC variability is positively correlated with the near-surface air temperature in Atlantic-European Arctic sector on a 10-year time scale

Electric field induced strong localization of electrons on solid hydrogen surface: possible applications to quantum computing

Two-dimensional electron system on the liquid helium surface is one of the leading candidates for constructing large analog quantum computers (P.M. Platzman and M.I. Dykman, Science 284, 1967 (1999)). Similar electron systems on the surfaces of solid hydrogen or solid neon may have some important advantages with respect to electrons on liquid helium in quantum computing applications, such as larger state separation $\Delta E$, absence of propagating capillary waves (or ripplons), smaller vapor pressure, etc. As a result, it may operate at higher temperatures. Surface roughness is the main hurdle to overcome in building a realistic quantum computer using these states. Electric field induced strong localization of surface electrons is shown to be a convenient tool to characterize surface roughness.Comment: 4 pages, 3 figure

Amplification of Fluctuations in Unstable Systems with Disorder

We study the early-stage kinetics of thermodynamically unstable systems with quenched disorder. We show analytically that the growth of initial fluctuations is amplified by the presence of disorder. This is confirmed by numerical simulations of morphological phase separation (MPS) in thin liquid films and spinodal decomposition (SD) in binary mixtures. We also discuss the experimental implications of our results.Comment: 15 pages, 4 figure

The effect of the probe magnetic moment orientation of magnetic resonance force microscope on the spectra of spin wave resonances

This work was supported by the Russian Science Foundation (project 16-12-10254)

Realizability of Polytopes as a Low Rank Matrix Completion Problem

This article gives necessary and sufficient conditions for a relation to be the containment relation between the facets and vertices of a polytope. Also given here, are a set of matrices parameterizing the linear moduli space and another set parameterizing the projective moduli space of a combinatorial polytope

Сценарии развития экономик развитых стран и России в условиях постпандемии

Amid the Kondratiev cycle's downward slope movement and global pandemic, a recession in many countries is Likely to Lead to a deep long-term economic crisis. The aim of the article is to study the simplest recession indicators in developing and developed countries, economic-recovery measures, and economic development scenarios. The objectives of the paper are to study current economic situations in different countries, including Russia; identify measures to prevent a recession in developing and developed countries; evaluate possible economic development scenarios with regard to the cyclical dynamics in the current climate. The authors used methods of analysis, modelling, monitoring of major economic indicators based on the data of past recessions and other crises. The results of the research show different scenarios of economic growth depending on the number of Covid-19 cases and the effectiveness of government’s responses to the pandemic; a correlation between monetary and fiscal policies in overcoming crisis; monetary policy priorities necessary for economic recovery; problems and prospects of monetary and fiscal policy implementation. The authors concluded that GDP, unemployment, and inflation rate are key indicators for the evaluation of the current and future money, credit, and production-related events. Proactive measures ensure a smoother average economic growth. Both monetary and fiscal policy have advantages and disadvantages. Proactive measures, in particular, inevitably cause two time lags: in the reaction to a recession and in the effectiveness of implemented measures. The governments and central banks must be proactive in overcoming the economic recession and providing support to the citizens.На фоне понижательной волны цикла Н.Д. Кондратьева и в условиях пандемии рецессия во многих странах может перейти в глубокий и долгосрочный экономический кризис. Цель статьи - описать наиболее понятные индикаторы рецессии в развивающихся и развитых странах, меры, принимаемые по предотвращению рецессии и оценить сценарии развития экономики. Для реализации данной цели авторы выполнили следующие задачи: исследовали современное состояние экономик разных стран, в том числе России; определили меры по предотвращению рецессии в развитых и развивающихся странах; рассмотрели сценарии развития экономики в современных условиях с учетом циклического характера экономической динамики. Использованы методы анализа, моделирования, мониторинга основных экономических показателей на основе ретроспективных данных, охватывающих несколько рецессий и аналогии. В результате исследования определены: пути развития экономики в зависимости от количества заболевших COVID-19 и эффективности государственных мер; взаимосвязь денежно-кредитной и фискальной политик при выходе из кризиса; приоритеты денежно-кредитной политики для восстановления экономики; проблемы и перспективы применения мер денежно-кредитной и фискальной политик. Сделан вывод, что показатели динамики ВВП, безработицы, инфляции являются полезными ориентирами для оценки текущих и будущих событий в области денежных средств, кредитов и производства. В современных условиях определена необходимость проактивных мер для более сглаженного среднего роста экономик. Каждая из двух описанных (монетарной или фискальной) политик имеет свои преимущества и недостатки. В частности, при выполнении проактивных мер в монетарной политике всегда наблюдается два временных лага: в реакции на рецессию и во времени влияния принимаемых мер. Для борьбы с рецессией в экономике правительствам и центральным банкам следует быть проактивными, что наиболее важно для населения

Microwave Absorption of Surface-State Electrons on Liquid 3^3He

We have investigated the intersubband transitions of surface state electrons (SSE) on liquid $^3$He induced by microwave radiation at temperatures from 1.1 K down to 0.01 K. Above 0.4 K, the transition linewidth is proportional to the density of $^3$He vapor atoms. This proportionality is explained well by Ando's theory, in which the linewidth is determined by the electron - vapor atom scattering. However, the linewidth is larger than the calculation by a factor of 2.1. This discrepancy strongly suggests that the theory underestimates the electron - vapor atom scattering rate. At lower temperatures, the absorption spectrum splits into several peaks. The multiple peak structure is partly attributed to the spatial inhomogeneity of the static holding electric field perpendicular to the electron sheet.Comment: 15 pages, 7 figures, submitted to J. Phys. Soc. Jp

Microwave saturation of the Rydberg states of electrons on helium

We present measurements of the resonant microwave excitation of the Rydberg energy levels of surface state electrons on superfluid helium. The temperature dependent linewidth agrees well with theoretical predictions and is very small below 300 mK. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency was determined as a function of microwave power. The high values of the ratio of the Rabi frequency to linewidth confirm this system as an excellent candidate for creating qubits.Comment: 4 pages, 4 figure