Self-Organization in Multimode Microwave Phonon Laser (Phaser): Experimental Observation of Spin-Phonon Cooperative Motions

An unusual nonlinear resonance was experimentally observed in a ruby phonon laser (phaser) operating at 9 GHz with an electromagnetic pumping at 23 GHz. The resonance is manifested by very slow cooperative self-detunings in the microwave spectra of stimulated phonon emission when pumping is modulated at a superlow frequency (less than 10 Hz). During the self-detuning cycle new and new narrow phonon modes are sequentially ``fired'' on one side of the spectrum and approximately the same number of modes are ``extinguished'' on the other side, up to a complete generation breakdown in a certain final portion of the frequency axis. This is usually followed by a short-time refractority, after which the generation is fired again in the opposite (starting) portion of the frequency axis. The entire process of such cooperative spectral motions is repeated with high degree of regularity. The self-detuning period strongly depends on difference between the modulation frequency and the resonance frequency. This period is incommensurable with period of modulation. It increases to very large values (more than 100 s) when pointed difference is less than 0.05 Hz. The revealed phenomenon is a kind of global spin-phonon self- organization. All microwave modes of phonon laser oscillate with the same period, but with different, strongly determined phase shifts - as in optical lasers with antiphase motions.Comment: LaTeX2e file (REVTeX4), 5 pages, 5 Postscript figures. Extended and revised version of journal publication. More convenient terminology is used. Many new bibliographic references are added, including main early theoretical and experimental papers on microwave phonon lasers (in English and in Russian

A fast total variation regularization algorithm for 2D piecewise constant radially symmetric functions

In this paper, total variation regularization (TV regularization) for 2D radially symmetric piecewise constant (RSPC) functions is considered. A system of equations solving the direct variational problem with the subgradient method is obtained. Using the system, we propose a Condat’s type algorithm for computation of an extremal function.The work was supported by the Ministry of Education and Science of Russian Federation (grant № 2.1743.2017)

A fast one dimensional total variation regularization algorithm

Denoising has numerous applications in communications, control, machine learning, and many other fields of engineering and science. A common way to solve the problem utilizes the total variation (TV) regularization. Many efficient numerical algorithms have been developed for solving the TV regularization problem. Condat described a fast direct algorithm to compute the processed 1D signal. In this paper, we propose a variant of the Condat’s algorithm based on the direct 1D TV regularization problem. The usage of the Condat algorithm with the taut string approach leads to a clear geometric description of the extremal function.The work was supported by Russian Science Foundation grant №15-19-10010

An efficient algorithm for non-rigid object registration

An efficient algorithm for registration of two non-rigid objects based on geometrical transformation of the template object to target object is proposed. The transformation is considered as warping of the template onto the target. To choose the most suitable transformation from all possible warps, a registration algorithm should satisfy deformation constraints referred to as regularization of non-rigid objects. In this work, we use variational functionals for affine transformations. With the help of computer simulation, the proposed method for searching the optimal geometrical transformation is compared with that of common algorithms

Affine registration of point clouds based on point-to-plane approach

The problem of aligning of 3D point data is the known registration task. The most popular registration algorithm is the Iterative Closest Point (ICP). This paper proposes a new algorithm for affine registration of point clouds by incorporating the affine transformation into the point-toplane ICP algorithm. At each iterative step of the algorithm, a closed-form solution for the affine transformation is derived.The work was supported by the Ministry of Education and Science of Russian Federation (grant № 2.1743.2017)

Approximation of the exact solution of point clouds registration based on point-to-plane approach for orthogonal transformations

The most popular algorithm for aligning of 3D point data is the Iterative Closest Point (ICP). This paper proposes a new algorithm for orthogonal registration of point clouds based on the point-to-plane ICP algorithm for affine transformation. At each iterative step of the algorithm, an approximation of the closed-form solution for the orthogonal transformation is derived.The work was supported by the Ministry of Education and Science of Russian Federation (grant № 2.1743.2017)

Exoplanets and SETI

The discovery of exoplanets has both focused and expanded the search for extraterrestrial intelligence. The consideration of Earth as an exoplanet, the knowledge of the orbital parameters of individual exoplanets, and our new understanding of the prevalence of exoplanets throughout the galaxy have all altered the search strategies of communication SETI efforts, by inspiring new "Schelling points" (i.e. optimal search strategies for beacons). Future efforts to characterize individual planets photometrically and spectroscopically, with imaging and via transit, will also allow for searches for a variety of technosignatures on their surfaces, in their atmospheres, and in orbit around them. In the near-term, searches for new planetary systems might even turn up free-floating megastructures.Comment: 9 page invited review. v2 adds some references and v3 has other minor additions and modification

СТРУКТУРНЫЕ И МАГНИТНЫЕ СВОЙСТВА ТВЕРДЫХ РАСТВОРОВ СИСТЕМЫ АНТИМОНИД КОБАЛЬТА–ТЕЛЛУРИД КОБАЛЬТА

By the method of melting special powder amounts of cobalt antimonide and cobalt telluride in vacuum, the solid solutions alloys of the CoSb1–x Tex system were synthesized with the NiAs structure. X-ray analysis results of the alloys confirmed the formation of a continuous series of solid solutions with a nickel-arsenide-type structure in the system. The constants a of the initial CoSb and CoTe compounds are close in values, which determines the course of the dependence a = f(x) that is practically parallel to the concentration axis. The dependence of the constant c on the concentration increases smoothly from 5.181 Å in CoSb to 5.371 Å in CoTe with a slight deflection to the concentration axis. The alloy density, determined by the hydrostatic weighing in carbon tetrachloride, has a linear dependence on the concentration. The concentration dependence of the micro hardness of the CoSb1–x Tex alloys passes through a weakly expressed maximum in the range of average compositions. Specific magnetization and magnetic susceptibility of the alloys are measured by the ponderomotive method in a magnetic field of 6.8 · 105 A/m in the temperature range 80–1200 K. At the temperature of liquid nitrogen, the value of specific magnetization is maximum (~6,0–6,5 Гс · см3 · г–1) in CoTe and solid solutions based on it. Solid solutions of compositions x = 0.4–0.9 have a magnetic transition temperature exceeding 1200 K. Методом плавления соответствующих количеств порошков соединений антимонида кобальта и теллурида кобальта в вакууме синтезированы сплавы твердых растворов системы CoSb1–x Tex . Результаты рентгеноструктурного анализа сплавов подтвердили образование в системе непрерывного ряда твердых растворов со структурой никель- арсенидного типа. Постоянные а исходных соединений CoSb и CoTe близки по величинам, что определяет практически параллельный оси концентрации ход зависимости a = f(x). Зависимость постоянной с от концентрации плавно возрастает от 5,181 Å у CoSb до 5,371 Å у CoTe с небольшим прогибом к оси концентраций. Плотность сплавов, определенная методом гидростатического взвешивания в тетрахлориде углерода, имеет линейный характер зависимости от концентрации. Концентрационная зависимость микротвердости сплавов системы CoSb1–x Tex проходит через слабо выраженный максимум в области средних составов. Пондеромоторным методом в магнитном поле 6,8 · 105 А/м в интервале температур 80–1200 К измерены удельная намагниченность и магнитная восприимчивость сплавов системы. При температуре жидкого азота величина удельной намагниченности максимальна (~6,0–6,5 Гс · см3 · г–1) у составов CoTe и CoSb0,1Te0,9 и практически равна нулю у CoSb и твердых растворов на его основе. Твердые растворы составов х = 0,4–0,9 обладают температурой магнитного перехода, превышающей 1200 К