435 research outputs found
Time dependent neutrino billiards
Quantum dynamica of a massless Dirac particle in time-dependent 1D box and
circular billiard with time-dependent radius is studied. An exact analytical
wave functions and eigenvalues are obtained for the case of linear
time-dependence of the boundary position
Creation of photons in an oscillating cavity with two moving mirrors
We study the creation of photons in a one dimensional oscillating cavity with
two perfectly conducting moving walls. By means of a conformal transformation
we derive a set of generalized Moore's equations whose solution contains the
whole information of the radiation field within the cavity. For the case of
resonant oscillations we solve these equations using a renormalization group
procedure that appropriately deals with the secular behaviour present in a
naive perturbative approach. We study the time evolution of the energy density
profile and of the number of created photons inside the cavity.Comment: LaTex file, 17 pages, 3 figures, uses epsf.st
Spectrum of the Vortex Bound States of the Dirac and Schrodinger Hamiltonian in the presence of Superconducting Gaps
We investigate the vortex bound states both Schrodinger and Dirac Hamiltonian
with the s-wave superconducting pairing gap by solving the mean-field
Bogoliubov-de-Gennes equations. The exact vortex bound states spectrum is
numerically determined by the integration method, and also accompanied by the
quasi-classical analysis. It is found that the bound state energies is
proportional to the vortex angular momentum when the chemical potential is
large enough. By applying the external magnetic field, the vortex bound state
energies of the Dirac Hamiltonian are almost unchanged; whereas the energy
shift of the Schrodinger Hamiltonian is proportional to the magnetic field.
These qualitative differences may serve as an indirect evidence of the
existence of Majorana fermions in which the zero mode exists in the case of the
Dirac Hamiltonian only.Comment: 8 pages, 9 figure
Motion-Induced Radiation from a Dynamically Deforming Mirror
A path integral formulation is developed to study the spectrum of radiation
from a perfectly reflecting (conducting) surface. It allows us to study
arbitrary deformations in space and time. The spectrum is calculated to second
order in the height function. For a harmonic traveling wave on the surface, we
find many different regimes in which the radiation is restricted to certain
directions. It is shown that high frequency photons are emitted in a beam with
relatively low angular dispersion whose direction can be controlled by the
mechanical deformations of the plate.Comment: 4 pages, 2 eps figues included, final version as appeared in PR
Effective Theoretical Approach to Back Reaction of the Dynamical Casimir Effect in 1+1 Dimensions
We present an approach to studying the Casimir effects by means of the
effective theory. An essential point of our approach is replacing the mirror
separation into the size of space S^1 in the adiabatic approximation. It is
natural to identify the size of space S^1 with the scale factor of the
Robertson-Walker-type metric. This replacement simplifies the construction of a
class of effective models to study the Casimir effects. To check the validity
of this replacement we construct a model for a scalar field coupling to the
two-dimensional gravity and calculate the Casimir effects by the effective
action for the variable scale factor. Our effective action consists of the
classical kinetic term of the mirror separation and the quantum correction
derived by the path-integral method. The quantum correction naturally contains
both the Casimir energy term and the back-reaction term of the dynamical
Casimir effect, the latter of which is expressed by the conformal anomaly. The
resultant effective action describes the dynamical vacuum pressure, i.e., the
dynamical Casimir force. We confirm that the force depends on the relative
velocity of the mirrors, and that it is always attractive and stronger than the
static Casimir force within the adiabatic approximation.Comment: Published Version, 16 pages, LaTeX2e with graphics package, 1 figur
Dynamical Casimir effect without boundary conditions
The moving-mirror problem is microscopically formulated without invoking the
external boundary conditions. The moving mirrors are described by the quantized
matter field interacting with the photon field, forming dynamical cavity
polaritons: photons in the cavity are dressed by electrons in the moving
mirrors. The effective Hamiltonian for the polariton is derived, and
corrections to the results based on the external boundary conditions are
discussed.Comment: 12 pages, 2 figure
Coherent dynamics of Bose-Einstein condensates in high-finesse optical cavities
We study the mutual interaction of a Bose-Einstein condensed gas with a
single mode of a high-finesse optical cavity. We show how the cavity
transmission reflects condensate properties and calculate the self-consistent
intra-cavity light field and condensate evolution. Solving the coupled
condensate-cavity equations we find that while falling through the cavity, the
condensate is adiabatically transfered into the ground state of the periodic
optical potential. This allows time dependent non-destructive measurements on
Bose-Einstein condensates with intriguing prospects for subsequent controlled
manipulation.Comment: 5 pages, 5 figures; revised version: added reference
Entangling Two Bose-Einstein Condensates by Stimulated Bragg Scattering
We propose an experiment for entangling two spatially separated Bose-Einstein
condensates by Bragg scattering of light. When Bragg scattering in two
condensates is stimulated by a common probe, the resulting quasiparticles in
the two condensates get entangled due to quantum communication between the
condensates via probe beam. The entanglement is shown to be significant and
occurs in both number and quadrature phase variables. We present two methods of
detecting the generated entanglement.Comment: 4 pages, Revte
Magnetism in a lattice of spinor Bose condensates
We study the ground state magnetic properties of ferromagnetic spinor
Bose-Einstein condensates confined in a deep optical lattices. In the Mott
insulator regime, the ``mini-condensates'' at each lattice site behave as
mesoscopic spin magnets that can interact with neighboring sites through both
the static magnetic dipolar interaction and the light-induced dipolar
interaction. We show that such an array of spin magnets can undergo a
ferromagnetic or anti-ferromagnetic phase transition under the magnetic dipolar
interaction depending on the dimension of the confining optical lattice. The
ground-state spin configurations and related magnetic properties are
investigated in detail
Momentum state engineering and control in Bose-Einstein condensates
We demonstrate theoretically the use of genetic learning algorithms to
coherently control the dynamics of a Bose-Einstein condensate. We consider
specifically the situation of a condensate in an optical lattice formed by two
counterpropagating laser beams. The frequency detuning between the lasers acts
as a control parameter that can be used to precisely manipulate the condensate
even in the presence of a significant mean-field energy. We illustrate this
procedure in the coherent acceleration of a condensate and in the preparation
of a superposition of prescribed relative phase.Comment: 9 pages incl. 6 PostScript figures (.eps), LaTeX using RevTeX,
submitted to Phys. Rev. A, incl. small modifications, some references adde
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