On the internal modes in sine-Gordon chain

We address the issue of internal modes of a kink of a discrete sine-Gordon equation. The main point of the present study is to elucidate how the antisymmetric internal mode frequency dependence enters the quasicontinuum spectrum of nonlocalized waves. We analyze the internal frequency dependencies as functions of both the number of cites and discreteness parameter and explain the origin of spectrum peculiarity which arises after the frequency dependence of antisymmetric mode returns back to the continuous spectrum at some nonzero value of the intersite coupling.Comment: 5 pages, 3 figure

Scattering of vortex pairs in 2D easy-plane ferromagnets

Vortex-antivortex pairs in 2D easy-plane ferromagnets have characteristics of solitons in two dimensions. We investigate numerically and analytically the dynamics of such vortex pairs. In particular we simulate numerically the head-on collision of two pairs with different velocities for a wide range of the total linear momentum of the system. If the momentum difference of the two pairs is small, the vortices exchange partners, scatter at an angle depending on this difference, and form two new identical pairs. If it is large, the pairs pass through each other without losing their identity. We also study head-tail collisions. Two identical pairs moving in the same direction are bound into a moving quadrupole in which the two vortices as well as the two antivortices rotate around each other. We study the scattering processes also analytically in the frame of a collective variable theory, where the equations of motion for a system of four vortices constitute an integrable system. The features of the different collision scenarios are fully reproduced by the theory. We finally compare some aspects of the present soliton scattering with the corresponding situation in one dimension.Comment: 13 pages (RevTeX), 8 figure

Group analysis and renormgroup symmetries

An original regular approach to constructing special type symmetries for boundary value problems, namely renormgroup symmetries, is presented. Different methods of calculating these symmetries, based on modern group analysis are described. Application of the approach to boundary value problems is demonstrated with the help of a simple mathematical model.Comment: 17 pages, RevTeX LATeX file, to appear in Journal of Mathematical Physic

Observational evidence for the origin of high-energy neutrinos in parsec-scale nuclei of radio-bright active galaxies

Observational information on high-energy astrophysical neutrinos is being continuously collected by the IceCube observatory. However, the sources of neutrinos are still unknown. In this study, we use radio very-long-baseline interferometry (VLBI) data for a complete VLBI-flux-density limited sample of active galactic nuclei (AGN). We address the problem of the origin of astrophysical neutrinos with energies above 200 TeV in a statistical manner. It is found that AGN positionally associated with IceCube events have typically stronger parsec-scale cores than the rest of the sample. The post-trial probability of a chance coincidence is 0.2%. We select the four strongest AGN as highly probable associations: 3C 279, NRAO 530, PKS 1741-038, and PKS 2145+067. Moreover, we find an increase of radio emission at frequencies above 10 GHz around neutrino arrival times for several other VLBI-selected AGN on the basis of RATAN-600 monitoring. The most pronounced example of such behavior is PKS 1502+106. We conclude that AGN with bright Doppler-boosted jets constitute an important population of neutrino sources. High-energy neutrinos are produced in their central parsec-scale regions, probably in proton-photon interactions at or around the accretion disk. Radio-bright AGN that are likely associated with neutrinos have very diverse gamma-ray properties suggesting that gamma-rays and neutrinos may be produced in different regions of AGN and not directly related. A small viewing angle of the jet-disk axis is, however, required to detect either of them.Comment: 19 pages, 5 figures, 3 tables; accepted to ApJ; v2: extended discussion, added a figure and electronic table; v3: fixed typo in a source nam

Clusteron structure of tick-borne encephalitis virus populations

Tick-borne encephalitis is a natural focal transmissible zooanthroponosis. The causative agent of the disease is a tick-borne encephalitis virus (TBEV) belonging to the genus Flavivirus of the family Flaviviridae and is widespread in Eurasia. Current TBEV classification based on molecular genetic data comprises three phylogenetically separate subtypes: Far Eastern, European and Siberian (TBEV-Sib). Further differentiation of TBEV isn't developed, making it difficult to investigate the origins, distribution and evolution of the virus. In the present study we determined the nucleotide sequence of the gene E fragment for 282 TBEV-Sib isolates from Ixodes persulcatus ticks or their pools from various natural foci in Russia. Analysis of these sequences and sequences obtained from the GenBank database (more than 600), made it possible to cluster TBEV-Sib strains by identical amino acid sequences of a glycoprotein E fragment. In total, 18 groups were identified (from 3 to 285 strains in the group). It was shown that TBEV strains belonging to the same group are phylogenetically related and have a territorial attachment showing either a local or a corridor type distribution. These groups were named as clusterons showed to be the smallest unit of TBEV classification. The grouping of TBEV strains allows characterization of endemic areas both in quantitative and qualitative composition of the clusterons. The approach could be successfully used to record and monitor the TBEV populations. © 2012 Elsevier B.V

The magnetic structure of a thin ferromagnetic film on the rough surface of an antiferromagnet

The magnetic structure (including domanization) of a thin ferromagnetic film in contact with a rigid antiferromagnet is investigated under the assumption that the interface is rough and contains individual atomic steps of different signs, isolated "dipole of the steps," and a space-ordered periodic system of steps of alternate signs

Properties of ferromagnetic film hysteresis, on the surface of a hard-magnetic antiferromagnet, with a domain structure

This is a theoretical investigation of the exchange bias phenomenon, and the properties of a thin magnetic film's magnetization hysteresis loop, on the rough surface of a hard-magnetic antiferromagnet. An interface model with a periodic structure of atomic steps is presented. These atomic steps are associated with a spatially inhomogeneous distribution of the ferromagnetic film magnetization, akin to a system of domain walls. This structure leads to a complicated external field dependence of magnetization: the hysteresis curve can assume an asymmetrical shape and "fall apart" into two hysteresis loops, divided by a "horizontal plateau," or an area with constant field-independent magnetization. Such field dependence behavior has been recently observed experimentally in different ferro/antiferromagnet systems. The field dependence of magnetization has been obtained analytically using the long-wave approximation for various characteristics of ferromagnetic film (its thickness, values of exchange interaction, and magnetic anisotropy), and the interface (the period of the inhomogeneous structure, and exchange interaction through the interface). The analytical results are confirmed by numerical calculations for the corresponding discrete model with a more complex interface structure