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V. A. Brazhnyi

Publications and source records attributed to V. A. Brazhnyi.

23 records · Page 2Linked to original sources
arXiv2004

Dynamics of matter solitons in weakly modulated optical lattices

It is shown that matter solitons can be effectively managed by means of smooth variations of parameters of optical lattices in which the condensate is loaded. The phenomenon is based on the effect of lattice modulations on the carrier wave transporting the soliton and that is why is well understood in terms of the effective mass approach, where a particular spatial configuration of the band structure is of primary importance. Linear, parabolic, and spatially localized modulations are considered as the case examples. It is shown that these defects can originate accelerating and oscillating motion of matter solitons as well as simulate soliton interaction with attractive and repulsive defects.

cond-mat.soft↗
arXiv2004

On classification of intrinsic localized modes for the Discrete Nonlinear Schrödinger Equation

We consider localized modes (discrete breathers) of the discrete nonlinear Schrödinger equation $i\frac{dψ_n}{dt}=ψ_{n+1}+ψ_{n-1}-2ψ_n+σ|ψ_n|^2ψ_n$, $σ=\pm1$, $n\in \mathbb{Z}$. We study the diversity of the steady-state solutions of the form $ψ_n(t)=e^{iωt}v_n$ and the intervals of the frequency, $ω$, of their existence. The base for the analysis is provided by the anticontinuous limit ($ω$ negative and large enough) where all the solutions can be coded by the sequences of three symbols "-", "0" and "+". Using dynamical systems approach we show that this coding is valid for $ω<ω^*\approx -3.4533$ and the point $ω^*$ is a point of accumulation of saddle-node bifurcations. Also we study other bifurcations of intrinsic localized modes which take place for $ω>ω^*$ and give the complete table of them for the solutions with codes consisting of less than four symbols.

cond-mat.other↗
arXiv2003

Hydrodynamic flow of expanding Bose-Einstein condensates

We study expansion of quasi-one-dimensional Bose-Einstein condensate (BEC) after switching off the confining harmonic potential. Exact solution of dynamical equations is obtained in framework of the hydrodynamic approximation and it is compared with the direct numerical simulation of the full problem showing excellent agreement at realistic values of physical parameters. We analyze the maximum of the current density and estimate the velocity of expansion. The results of the 1D analysis provides also qualitative understanding of some properties of BEC expansion observed in experiments.

cond-mat.soft↗
arXiv2003

On creation and evolution of dark solitons in Bose-Einstein condensates

Generation of dark solitons from large initial excitations and their evolution in a quasi-one-dimensional Bose-Einstein condensate trapped by a harmonic potential is studied analytically and numerically. In the case of a single deep soliton main characteristics of its motion such as a frequency and amplitude of oscillations are calculated by means of the perturbation theory which in the leading order results in a Newtonian dynamics, corrections to which are computed as well. It is shown that long-time dynamics of a dark soliton in a generic situation deviates substantially from outcomes of the naive application of the Ehrenfest theorem. We also consider three different techniques of controllable creation of multi-soliton structures (soliton trains) from large initial excitations and calculate their initial parameters (depths and velocities) with the use of a generalized Bohr-Sommerfeld quantization rule. Multi-soliton effects are discussed.

cond-mat.soft↗