4,708 research outputs found
The 1/N-expansion, quantum-classical correspondence and nonclassical states generation in dissipative higher-order anharmonic oscillators
We develop a method for the determination of thecdynamics of dissipative
quantum systems in the limit of large number of quanta N, based on the
1/N-expansion of Heidmann et al. [ Opt. Commun. 54, 189 (1985) ] and the
quantum-classical correspondence. Using this method, we find analytically the
dynamics of nonclassical states generation in the higher-order anharmonic
dissipative oscillators for an arbitrary temperature of a reservoir. We show
that the quantum correction to the classical motion increases with time
quadratically up to some maximal value, which is dependent on the degree of
nonlinearity and a damping constant, and then it decreases. Similarities and
differences with the corresponding behavior of the quantum corrections to the
classical motion in the Hamiltonian chaotic systems are discussed. We also
compare our results obtained for some limiting cases with the results obtained
by using other semiclassical tools and discuss the conditions for validity of
our approach.Comment: 15 pages, RevTEX (EPSF-style), 3 figs. Replaced with final version
(stylistic corrections
A dynamical collective calculation of supernova neutrino signals
We present the first calculations with three flavors of collective and shock
wave effects for neutrino propagation in core-collapse supernovae using
hydroynamical density profiles and the S matrix formalism. We explore the
interplay between the neutrino-neutrino interaction and the effects of multiple
resonances upon the time signal of positrons in supernova observatories. A
specific signature is found for the inverted hierarchy and a large third
neutrino mixing angle and we predict, in this case, a dearth of lower energy
positrons in Cherenkov detectors midway through the neutrino signal and the
simultaneous revelation of valuable information about the original fluxes. We
show that this feature is also observable with current generation neutrino
detectors at the level of several sigmas.Comment: 4 pages, 5 figure
Equilibrium configurations of two charged masses in General Relativity
An asymptotically flat static solution of Einstein-Maxwell equations which
describes the field of two non-extreme Reissner - Nordstr\"om sources in
equilibrium is presented. It is expressed in terms of physical parameters of
the sources (their masses, charges and separating distance). Very simple
analytical forms were found for the solution as well as for the equilibrium
condition which guarantees the absence of any struts on the symmetry axis. This
condition shows that the equilibrium is not possible for two black holes or for
two naked singularities. However, in the case when one of the sources is a
black hole and another one is a naked singularity, the equilibrium is possible
at some distance separating the sources. It is interesting that for
appropriately chosen parameters even a Schwarzschild black hole together with a
naked singularity can be "suspended" freely in the superposition of their
fields.Comment: 4 pages; accepted for publication in Phys. Rev.
Optical chaos in nonlinear photonic crystals
We examine a spatial evolution of lightwaves in a nonlinear photonic crystal
with a quadratic nonlinearity when simultaneously a second harmonic and a
sum-frequency generation are quasi-phase-matched. We find the conditions of a
transition to Hamiltonian chaos for different amplitudes of lightwaves at the
boundary of the crystal.Comment: LaTEX2e, 5 pages, 4 figure
Direct current generation due to harmonic mixing: From bulk semiconductors to semiconductor superlattices
We discuss an effect of dc current and dc voltage (stopping bias) generation
in a semiconductor superlattice subjected by an ac electric field and its
phase-shifted n-th harmonic. In the low field limit, we find a simple
dependence of dc voltage on a strength, frequency, and relative phase of mixing
harmonics for an arbitrary even value of n.
We show that the generated dc voltage has a maximum when a frequency of ac
field is of the order of a scattering constant of electrons in a superlattice.
This means that for typical semiconductor superlattices at room temperature
operating in the THz frequency domain the effect is really observable.
We also made a comparison of a recent paper describing an effect of a
directed current generation in a semiconductor superlattice subjected by ac
field and its second harmonic (n=2) [K.Seeger, Appl.Phys.Lett. 76(2000)82] with
our earlier findings describing the same effect [K.Alekseev et al., Europhys.
Lett. 47(1999)595; cond-mat/9903092 ].
For the mixing of an ac field and its n-th harmonic with n>=4, we found that
additionally to the phase-shift controlling of the dc current, there is a
frequency control. This frequency controlling of the dc current direction is
absent in the case of n=2. The found effect is that, both the dc current
suppression and the dc current reversals exist for some particular values of ac
field frequency. For typical semiconductor superlattices such an interesting
behavior of the dc current should be observable also in the THz domain.
Finally, we briefly review the history of the problem of the dc current
generation at mixing of harmonics in semiconductors and semiconductor
microstructures.Comment: 9 pages, 1 figure, RevTEX, EPS
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