Keldysh’s theory of a rarefied superfluid electron-hole gas is extended to the case of possible pair polarization. It is established that the complex order parameter Φ(r1,r2), which is the wave function of a pair, satisfies a nonlinear, nonlocal, integrodifferential equation. The equation obtained is solved for the order parameter varying slowly over a distance of the order of the pair size. The dipole-moment density of the system is found from the known function Φ(r1,r2), and it is shown that the inhomogeneity of the system engenders a dipole moment proportional and oriented parallel to the gradient of the particle density. It is determined that an additional dipole moment associated with pair polarization due to the Lorentz force appears in a magnetic field.
The Keldysh's theory of superfluidity of rarefied electron-hole gas is generalized to a case of possible pair polarizability. It was shown that inhomogeneity of the system leads to dipole moment which is proportional to the density gradient. The dipole moment appears also near boundaries of the system. It was determined that quantized vortices in a magnetic field carry a real electric charge. In He II at H=10 T and helium rotation velocity $10^2$ s$^{-1}$ the charge density is about $10^4e$ cm$^{-3}$, where $e$ is the electron charge.Comment: 5 pages V. 2: replaced incorrect g valu
The issue of adequate describing a gas of complex particles, composed of an even number of fermions, as point bosons is studied in alkali metals. In the low-density approximation we obtain the equation for the complex order parameter Φ(r1, r2) representing the wave function of atoms with taking into account the internal motion of the valence electrons. For superfluid systems formed by particles with internal degrees of freedom, this equation replaces the Gross-Pitaevskii equation. It is shown that, in general, exchange effects should be considered in the same approximation as effects of the direct interaction of atoms with each other. In particular, in the case of only the Coulomb interaction the neglect of exchange effects leads to qualitatively incorrect results. The problem of spontaneous polarization in superfluid systems is studied. The expression for the electric polarization of the inhomogeneous superfluid system is obtained.
The electric polarization appearing in superfluid systems as a result of their inhomogeneity is studied. The problem is studied using the rarefied electron-hole gas model which the authors studied previously. A microscopic calculation is performed of the polarization of quantum vortices in the absence and presence of a magnetic field. It is established that in the presence of a magnetic field vortices acquire additional polarization, which results in the appearance of a quantized charge in a vortex core. It is shown that the van-der-Waals interaction of a superfluid system with a solid surface gives rise to polarization near the surface. A relation is established between the results obtained and the prediction of possible polarization of the medium in nonuniform motion.
It is shown that in a magnetic field quantized vortices in a superfluid obtain a real quantized electric charge concentrated in the vortex core. This charge is compensated by an opposite surface charge located at a macroscopic distance from the vortex axis. It is determined that the polarization caused by the vortex velocity field does not give rise to electric fields outside an infinite cylinder. Observation of electric fields created by the vortices is possible only near the end surfaces of the cylinder which must be closed with dielectric covers to prevent superfluid leaking. Influence of cover properties on the potential created by the vortex is researched. Potential created by the vortices on point and ring electrodes are calculated. were undertaken to understand the nature of the observed phenomena, but they are unsuccessful up to date. However, several interesting results were obtained which concern the mechanisms of polarization of both superfluid and normal systems. For example, in Melnikovskiy's article [4] it is shown that accelerated motion of a dielectric medium leads to its polarization proportional to the acceleration. Natsik [5] - [7] has studied the peculiarities of polarization of superfluid systems and, developing Melnikovskiy's ideas, has found that vortex motion of atoms in a superfluid must lead to their polarization caused by centrifugal force acting on them. In this case the polarization vector is directed normally to the velocity of the fluid moving around the vortex line, so the polarization vectors form a "hedgehog". Unfortunately, observation of electric fields caused by this "hedgehog" is rather difficult due to their rapid decrease with distance from the vortex line (reverse proportional to the cube of the distance). The authors [14] - [16] found that in a magnetic field the vortex line acquires a real electric charge whose magnitude is proportional to the vortex circulation and is quantized in the same way as the circulation. The compensating charge of the opposite sign appears on the surface of the system. Macroscopic spatial separation of the vortex charge and the compensating one allows to measure the electric field caused by these charges and to observe the motion of vortices in the superfluid. In this message we discuss the significant aspects of measuring the electric fields generated by the vortices.First we recall the arguments of the articles [14] -[16]. In a magnetic field H a rarefied medium moving with velocity v acquires polarizationHere α is the atom polarizability, n is the medium den- * Electronic address: shevchenko@ilt.kharkov.ua sity, c is the velocity of light. It follows from the common expression for the electric induction of the moving mediumwhere µ is the magnetic permeability, that the expression (1) for the dipole moment P is valid when µ = 1 and ǫ = 1 + 4πnα. In a superfluid there exists a "characteristic configuration" of the velocity field v caused by a vortex,Here φ is the phase of the order parameter. In the case of a rectilinear vortex in a uniform m...
The purpose of the work was to study the effectiveness of resources and services of the information and educational environment of the university, in particular, the information and educational portal Moodle in distance learning of students. Materials and methods. Two main aspects of the solution of the problem of informatization of education – computerization of educational institutions and acquisition of information and communication competences by scientific and pedagogical staff of universities – were considered. Results and discussion. The article outlines the challenges and possible directions of work in the second aspect, namely the need for academic educators to understand the State’s e-learning policy, how to plan their learning process using information and communication technology, the ability to use innovative pedagogical distance learning technologies and the ability to create new, in-house e-learning resources. The need for continuous professional development of professors in the application of innovative educational technologies was emphasized. Consideration was given to the experience gained in the implementation of the problem of improving the qualifications of scientific and pedagogical staff in the use of information and communication technologies and in the creation of an information and educational environment at the Kharkiv National Medical University through the establishment of the Distance Learning Centre of the Scientific and Training Institute for the Quality of Education of Kharkiv National Medical University. The possibilities of the Moodle information educational portal in the organization of distance learning are considered. One of the types of advanced training – the course on the basics of developing electronic learning courses was analyzed. The definition of an electronic learning course, its structure, main characteristics, an algorithm for creating, approbation and accreditation based on the experience of organizing distance learning at Kharkiv National Medical University are considered. Conclusion. The expediency of introducing distance learning courses into the educational process is argued and the experience of creating and testing a distance learning course in the discipline "Modern problems of biophysics" for students of the dental faculty of Kharkiv National Medical University is discussed
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