2,818 research outputs found
How Well a Chaotic Quantum System Can Retain Memory of Its Initial State?
In classical mechanics the local exponential instability effaces the memory
of initial conditions and leads to practical irreversibility. In striking
contrast, quantum mechanics appears to exhibit strong memory of the initial
state. We relate the latter fact to the low (at most linear) rate with which
the system's Wigner function gets during evolution more and more complicated
structure and establish existence of a critical strength of external influence
below which such a memory still survives.Comment: 5 pages, 4 figure
Plasma dispersion of multisubband electron systems over liquid helium
Density-density response functions are evaluated for nondegenerate
multisubband electron systems in the random-phase approximation for arbitrary
wave number and subband index. We consider both quasi-two-dimensional and
quasi-one- dimensional systems for electrons confined to the surface of liquid
helium. The dispersion relations of longitudinal intrasubband and transverse
intersubband modes are calculated at low temperatures and for long wavelengths.
We discuss the effects of screening and two-subband occupancy on the plasmon
spectrum. The characteristic absorption edge of the intersubband modes is
shifted relatively to the single-particle intersubband separation and the
depolarization shift correction can be significant at high electron densities
Fractional Klein-Kramers equation for superdiffusive transport: normal versus anomalous time evolution in a differential L{\'e}vy walk model
We introduce a fractional Klein-Kramers equation which describes
sub-ballistic superdiffusion in phase space in the presence of a
space-dependent external force field. This equation defines the differential
L{\'e}vy walk model whose solution is shown to be non-negative. In the velocity
coordinate, the probability density relaxes in Mittag-Leffler fashion towards
the Maxwell distribution whereas in the space coordinate, no stationary
solution exists and the temporal evolution of moments exhibits a competition
between Brownian and anomalous contributions.Comment: 4 pages, REVTe
Coupled phonon-ripplon modes in a single wire of electrons on the liquid-helium surface
The coupled phonon-ripplon modes of the quasi-one-dimensional electron chain
on the liquid helium sutface are studied. It is shown that the electron-ripplon
coupling leads to the splitting of the collective modes of the wire with the
appearance of low-frequency modes and high-frequency optical modes starting
from threshold frequencies. The effective masses of an electron plus the
associated dimple for low frequency modes are estimated and the values of the
threshold frequencies are calculated. The results obtained can be used in
experimental attempts to observe the phase transition of the electron wire into
a quasi-ordered phase.Comment: 5 pages, 1 figure, Physical Review (in press
Classification of integrable Volterra type lattices on the sphere. Isotropic case
The symmetry approach is used for classification of integrable isotropic
vector Volterra lattices on the sphere. The list of integrable lattices
consists mainly of new equations. Their symplectic structure and associated PDE
of vector NLS-type are discussed.Comment: 16 page
Quantum Resonances of Kicked Rotor and SU(q) group
The quantum kicked rotor (QKR) map is embedded into a continuous unitary
transformation generated by a time-independent quasi-Hamiltonian. In some
vicinity of a quantum resonance of order , we relate the problem to the {\it
regular} motion along a circle in a -component inhomogeneous
"magnetic" field of a quantum particle with intrinsic degrees of freedom
described by the group. This motion is in parallel with the classical
phase oscillations near a non-linear resonance.Comment: RevTeX, 4 pages, 3 figure
CPT and Lorentz violation effects in hydrogen-like atoms
Within the framework of Lorentz-violating extended electrodynamics, the Dirac
equation for a bound electron in an external electromagnetic field is
considered assuming the interaction with a CPT-odd axial vector background
. The quasi-relativistic Hamiltonian is obtained using a -series
expansion. Relativistic Dirac eigenstates in a spherically-symmetric potential
are found accurate up to the second order in . -induced CPT-odd
corrections to the electromagnetic dipole moment operators of a bound electron
are calculated that contribute to the anapole moment of the atomic orbital and
may cause a specific asymmetry of the angular distribution of the radiation of
a hydrogen atom.Comment: 13 pages, 1 figure; (5.14) is corrected to conform to the
normalization convention for Laguerre polynomials adopted at present; minor
grammatical change
Formation of bound states of electrons in spherically symmetric oscillations of plasma
We study spherically symmetric oscillations of electrons in plasma in the
frame of classical electrodynamics. Firstly, we analyze the electromagnetic
potentials for the system of radially oscillating charged particles. Secondly,
we consider both free and forced spherically symmetric oscillations of
electrons. Finally, we discuss the interaction between radially oscillating
electrons through the exchange of ion acoustic waves. It is obtained that the
effective potential of this interaction can be attractive and can transcend the
Debye-Huckel potential. We suggest that oscillating electrons can form bound
states at the initial stages of the spherical plasma structure evolution. The
possible applications of the obtained results for the theory of natural
plasmoids are examined.Comment: 9 pages in LaTeX2e, no figures; paper was significantly modified, 2
new references added, some inessential mathematics was removed, many typos
were corrected; final variant to be published in Physica Script
Diffusion mechanisms of localised knots along a polymer
We consider the diffusive motion of a localized knot along a linear polymer
chain. In particular, we derive the mean diffusion time of the knot before it
escapes from the chain once it gets close to one of the chain ends.
Self-reptation of the entire chain between either end and the knot position,
during which the knot is provided with free volume, leads to an L^3 scaling of
diffusion time; for sufficiently long chains, subdiffusion will enhance this
time even more. Conversely, we propose local ``breathing'', i.e., local
conformational rearrangement inside the knot region (KR) and its immediate
neighbourhood, as additional mechanism. The contribution of KR-breathing to the
diffusion time scales only quadratically, L^2, speeding up the knot escape
considerably and guaranteeing finite knot mobility even for very long chains.Comment: 7 pages, 2 figures. Accepted to Europhys. Let
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