Chirality inversion and radius blow-up of a N\'eel-type skyrmion by a Pearl vortex

We develop a theory for the coaxial configuration of a N\'eel-type skyrmion and a Pearl vortex in thin superconductor-chiral ferromagnetic heterostructures. Using direct numerical solution of the Euler-Lagrange equation and micromagnetic simulations we demonstrate that the inhomogeneous magnetic field of the Pearl vortex significantly modifies the skyrmion profile with respect to the one in the absence of the vortex. We discover drastic enlargement of the skyrmion's radius and inversion of the skyrmion's chirality. To unravel physics behind these effects we invent novel two-parameter ansatz for the magnetization profile of the skyrmion in the presence of the vortex. Chirality inversion and radius blow-up are controlled not only by the material parameters of the heterostructure but also by the thickness of the superconductor. Our findings can have implications for Majorana modes localized at skyrmion-vortex pairs.Comment: 6 pages, 2 figures; 1 video file and its description (as ancillary files

Laser Conoscopy Study of Optical Anomalies in Uniaxial Crystals

New experimental possibilities of detecting fine optical anomalies in uniaxial crystals are demonstrated on a level with numerical estimation of refractive index and mechanical stress variations that cause distortions of the optical indicatrix. New possibilities are due to the use of an exact equation for isochromes derived for uniaxial crystals without mathematical simplifications commonly used by other authors. It allows one to calculate and graphically reproduce the theoretical form of isochromes of any orders in the conoscopic picture of an ideal crystal with known principal refractive indices, the thickness and orientation of the crystal surfaces, and also the wavelength of the radiation and the parameters of the optical circuit. A computer comparison of the theoretical image with an experimental conoscopic picture of a real crystal, fixed by a color digital camera on a semitransparent screen, is performed. The data on the variations of refractive indices and mechanical stresses in the crystal are retrieved from the mathematical processing of differences in the conoscopic images. The applications of the proposed method for the analysis of optical homogeneity of paratellurite and lithium niobate single crystals are presented. Keywords: method of conoscopy, isochromes, piezo-optic effec

Assessment of the impact of the educational process on motor activity and health level of cadets of educational institutions of the ministry of internal affairs of Russia

The important components of the physical training of internal affairs officers, as well as other specialists, are the level of physical activity and quality health indicators. These components will determine the physical fitness of law enforcement specialists, not to mention the effectiveness of their duties. Graduates of general educational institution entering the educational organizations of the Ministry of Internal Affairs of Russia make the first step towards the development of the identity of a law enforcement officer. Therefore, the level of future professional knowledge, skills, and abilities, as well as competencies during their study at a higher education institution will determine the ability of a police officer to cope with his/her official dutie

Decay of metastable current states in one-dimensional resonant tunneling devices

Current switching in a double-barrier resonant tunneling structure is studied in the regime where the current-voltage characteristic exhibits intrinsic bistability, so that in a certain range of bias two different steady states of current are possible. Near the upper boundary V_{th} of the bistable region the upper current state is metastable, and because of the shot noise it eventually decays to the stable lower current state. We find the time of this switching process in strip-shaped devices, with the width small compared to the length. As the bias V is tuned away from the boundary value V_{th} of the bistable region, the mean switching time \tau increases exponentially. We show that in long strips \ln\tau \propto (V_{th} -V)^{5/4}, whereas in short strips \ln\tau \propto (V_{th} -V)^{3/2}. The one-dimensional geometry of the problem enables us to obtain analytically exact expressions for both the exponential and the prefactor of \tau. Furthermore, we show that, depending on the parameters of the system, the switching can be initiated either inside the strip, or at its ends.Comment: 12 pages, 5 figures, update to published versio

Spin resonance in a Luttinger liquid with spin-orbit interaction

Spin-orbit interaction in quantum wires leads to a spin resonance at low temperatures, even in the absence of an external dc magnetic field. We study the effect of electron-electron interaction on the resonance. This interaction is strong in quantum wires. We show that the electron-electron interaction changes the shape of the resonance curve and produces an additional cusp at the plasmon frequency. However, except for very strong electron-electron interaction these changes are weak since this interaction by itself does not break the spin-rotation symmetry that is violated weakly by the spin-orbit interaction and external magnetic field.Comment: 8 pages (including 3 pages of supplementary material), 2 figure

Geometric Random Inner Products: A New Family of Tests for Random Number Generators

We present a new computational scheme, GRIP (Geometric Random Inner Products), for testing the quality of random number generators. The GRIP formalism utilizes geometric probability techniques to calculate the average scalar products of random vectors generated in geometric objects, such as circles and spheres. We show that these average scalar products define a family of geometric constants which can be used to evaluate the quality of random number generators. We explicitly apply the GRIP tests to several random number generators frequently used in Monte Carlo simulations, and demonstrate a new statistical property for good random number generators

Lifetime of metastable states in resonant tunneling structures

We investigate the transport of electrons through a double-barrier resonant-tunneling structure in the regime where the current-voltage characteristics exhibit bistability. In this regime one of the states is metastable, and the system eventually switches from it to the stable state. We show that the mean switching time grows exponentially as the voltage across the device is tuned from the its boundary value into the bistable region. In samples of small area we find that the logarithm of the lifetime is proportional to the voltage (measured from its boundary value) to the 3/2 power, while in larger samples the logarithm of the lifetime is linearly proportional to the voltage.Comment: REVTeX 4, 5 pages, 3 EPS-figure