Variational formalism for the Klein-Gordon oscillon

The variational method employing the amplitude and width as collective coordinates of the Klein-Gordon oscillon leads to a dynamical system with unstable periodic orbits that blow up when perturbed. We propose a multiscale variational approach free from the blow-up singularities. An essential feature of the proposed trial function is the inclusion of the third collective variable: a correction for the nonuniform phase growth. In addition to determining the parameters of the oscillon, our approach detects the onset of its instability.Comment: 10 pages, 4 figure

Biodiversity of Small Mammals and Paleoenvironment of Transbaikalia and North Mongolia in the Late Pliocene

This paper reports the results of analysis on small mammal faunas dwelling during the Late Pliocene the Transbaikal and Northern Mongolia regions. They were found to share many common species, even though some differences linked with local and regional specifics of the environment are the case. High diversity of small mammal taxa, species richness and their prominent quantity specify the localities of Udunga, Beregovaya and Tologoi in Transbaikal region and in Shamar of Northern Mongolia. The compositions of all faunas point to the existence of the savanna-like landscapes and warm semiarid climate in that period

THz parametric gain in semiconductor superlattices in the absence of electric domains

We theoretically show that conditions for THz gain and conditions for formation of destructive electric domains in semiconductor superlattices are fairly different in the case of parametric generation and amplification. Action of an unbiased high-frequency electric field on a superlattice causes a periodic variation of energy and effective mass of miniband electrons. This parametric effect can result in a significant gain at some even harmonic of the pump frequency without formation of electric domains and corruption from pump harmonics.Comment: 4 pages, 3 figures. Accepted to Appl. Phys. Let

Optical solitons in PT\mathcal{PT}-symmetric nonlinear couplers with gain and loss

We study spatial and temporal solitons in the $\mathcal{PT}$ symmetric coupler with gain in one waveguide and loss in the other. Stability properties of the high- and low-frequency solitons are found to be completely determined by a single combination of the soliton's amplitude and the gain/loss coefficient of the waveguides. The unstable perturbations of the high-frequency soliton break the symmetry between its active and lossy components which results in a blowup of the soliton or a formation of a long-lived breather state. The unstable perturbations of the low-frequency soliton separate its two components in space blocking the power drainage of the active component and cutting the power supply to the lossy one. Eventually this also leads to the blowup or breathing.Comment: 14 pages, 11 figure