Underbarrier nucleation kinetics in a metastable quantum liquid near the spinodal

We develop a theory in order to describe the effect of relaxation in a condensed medium upon the quantum decay of a metastable liquid near the spinodal at low temperatures. We find that both the regime and the rate of quantum nucleation strongly depend on the relaxation time and its temperature behavior. The quantum nucleation rate slows down with the decrease of the relaxation time. We also discuss the low temperature experiments on cavitation in normal $^3$He and superfluid $^4$He at negative pressures. It is the sharp distinctions in the high frequency sound mode and in the temperature behavior of the relaxation time that make the quantum cavitation kinetics in $^3$He and $^4$He completely different in kind.Comment: 10 pages, 2 figure

Optical fiber beam loss monitor for the PHIL and ThomX facilities

ISBN 978-3-95450-132-8International audienceFiber beam loss monitor (FBLM) is an attractive solution to measure beam losses intensity and position in real time. It is a very useful tool, especially, for the commissioning and the beam alignment. In this article we report on the development of the FBLM at PHIL (PHotoinIector at LAL, Orsay, France) as a prototype of the beam loss monitor for the ThomX machine, the compact Compton based X-ray source being in the construction phase in Orsay

Backflow and dissipation during the quantum decay of a metastable Fermi liquid

The particle current in a metastable Fermi liquid against a first-order phase transition is calculated at zero temperature. During fluctuations of a droplet of the stable phase, in accordance with the conservation law, not only does an unperturbed current arise from the continuity at the boundary, but a backflow is induced by the density response. Quasiparticles carrying these currents are scattered by the boundary, yielding a dissipative backflow around the droplet. An energy of the hydrodynamic mass flow of the liquid and a friction force exerted on the droplet by the quasiparticles have been obtained in terms of a potential of their interaction with the droplet.Comment: 5 pages (REVTeX), to be published in Phys. Rev.

Exact Haldane mapping for all SS and super universality in spin chains

The low energy dynamics of the anti-ferromagnetic Heisenberg spin $S$ chain in the semiclassical limit $S\to\infty$ is known to map onto the O(3) nonlinear $\sigma$ model with a $\theta$ term in 1+1 dimension. Guided by the underlying dual symmetry of the spin chain, as well as the recently established topological significance of "dangling edge spins," we report an {\em exact} mapping onto the O(3) model that avoids the conventional large $S$ approximation altogether. Our new methodology demonstrates all the super universal features of the $\theta$ angle concept that previously arose in the theory of the quantum Hall effect. It explains why Haldane's original ideas remarkably yield the correct answer in spite of the fundamental complications that generally exist in the idea of semiclassical expansions

Energy relaxation in the spin-polarized disordered electron liquid

The energy relaxation in the spin-polarized disordered electron systems is studied in the diffusive regime. We derived the quantum kinetic equation in which the kernel of electron-electron collision integral explicitly depends on the electron magnetization. As the consequence, the inelastic scattering rate is found to have non-monotonic dependence on the spin polarization of the electron system

Domain wall effects in ferromagnet-superconductor structures

We investigate how domain structure of the ferromagnet in superconductor-ferromagnet heterostructures may change their transport properties. We calculate the distribution of current in the superconductor induced by magnetic field of Bloch domain walls, find the ``lower critical'' magnetization of the ferromagnet that provides vortices in the superconductor

Spin and Charge Correlations in Quantum Dots: An Exact Solution

The inclusion of charging and spin-exchange interactions within the Universal Hamiltonian description of quantum dots is challenging as it leads to a non-Abelian action. Here we present an {\it exact} analytical solution of the probem, in particular, in the vicinity of the Stoner instabilty point. We calculate several observables, including the tunneling density of states (TDOS) and the spin susceptibility. Near the instability point the TDOS exhibits a non-monotonous behavior as function of the tunneling energy, even at temperatures higher than the exchange energy. Our approach is generalizable to a broad set of observables, including the a.c. susceptibility and the absorption spectrum for anisotropic spin interaction. Our results could be tested in nearly ferromagnetic materials.Comment: JETPL class, 6 pages, 2 figure

Info-Communicative and Protective Function of the State as Combating Fraud using Sberbank Bank Cards

Financial crimes are defined as unfair activities that have become widespread in banking structures. The activities of financial fraudsters often have negative consequences before public rules are created that prohibit them. Intensive transformation processes in financial markets, their automation and virtualisation, the spread of remote interaction between banks and their clients, the influence of unauthorised persons on the software and hardware systems of banks, an increase in the number of cases and trading volumes determine the relevance of clarifying the essence of this phenomenon and the peculiarities of its manifestation in banking structures. The novelty of the study is determined by the fact that financial violations can be represented both in the structure of the current activities of banks and the process of interaction with clients and in the structure of expanding the list of services provided. The leading method to study this problem is the method of analysis, which allows to identify and comprehensively consider ways to counter financial crimes in banks to improve the level of financial security. The authors show that structurally, one should take into account, first of all, countermeasures on the part of customers, which often serve as a source of obtaining personal data. In this case, the state function is considered only as a security function for the purpose of possible punishment for fraudulent actions. The practical significance of the study is determined by the possibilities of structural implementation of combating financial fraudulent actions in the context of the development of the information society

The effects of liquid-phase oxidation of multiwall carbon nanotubes on their surface characteristics

The development of new sorbents based on nanostructured carbon materials recently became a perspective field of research. Main topic of current study is to investigate the effect of different regimes of multiwall carbon nanotubes (MWCNT) surface modification process on their structural characteristics. MWCNT samples were treated with nitric acid at high temperature. Structural properties were studied using low temperature nitrogen adsorption and acid-base back titration methods. The study showed that diluted nitric acid does not affect MWCNT structure. Concentrated nitric acid treatment leads to formation of 2.8 carboxylic groups per 1 nm{2} of the sample surface