4,209 research outputs found
Quench dynamics of a disordered array of dissipative coupled cavities
We investigate the mean-field dynamics of a system of interacting photons in
an array of coupled cavities in presence of dissipation and disorder. We follow
the evolution of on an initially prepared Fock state, and show how the
interplay between dissipation and disorder affects the coherence properties of
the cavity emission and that these properties can be used as signatures of the
many-body phase of the whole array.Comment: 8 pages, 10 figures, new reference adde
Exotic attractors of the non-equilibrium Rabi-Hubbard model
We explore the phase diagram of the dissipative Rabi-Hubbard model, as could
be realized by a Raman-pumping scheme applied to a coupled cavity array. There
exist various exotic attractors, including ferroelectric, antiferroelectric,
and inccomensurate fixed points, as well as regions of persistent oscillations.
Many of these features can be understood analytically by truncating to the two
lowest lying states of the Rabi model on each site. We also show that these
features survive beyond mean-field, using Matrix Product Operator simulations.Comment: 5pages, 3 figures, plus supplementary material. Final version, as
publishe
Field-induced superconductor to insulator transition in Josephson-junction ladders
The superconductor to insulator transition is studied in a self-charging
model for a ladder of Josephson-junctions in presence of an external magnetic
field. Path integral Monte Carlo simulations of the equivalent
(1+1)-dimensional classical model are used to study the phase diagram and
critical behavior. In addition to a superconducting (vortex-free) phase, a
vortex phase can also occur for increasing magnetic field and small charging
energy. It is found that an intervening insulating phase separates the
superconducting from the vortex phases. Surprisingly, a finite-size scaling
analysis shows that the field-induced superconducting to insulator transition
is in the KT universality class even tough the external field breaks
time-reversal symmetry.Comment: 5 pages, 7 figures, to appear in Phys. Rev.
Signatures of the super fluid-insulator phase transition in laser driven dissipative nonlinear cavity arrays
We analyze the non-equilibrium dynamics of a gas of interacting photons in an
array of coupled dissipative nonlinear cavities driven by a pulsed external
coherent field. Using a mean-field approach, we show that the system exhibits a
phase transition from a Mott-insulator-like to a superfluid regime. For a given
single-photon nonlinearity, the critical value of the photon tunneling rate at
which the phase transition occurs increases with the increasing photon loss
rate. We checked the robustness of the transition by showing its insensitivity
to the initial state prepared by the the pulsed excitation. We find that the
second-order coherence of cavity emission can be used to determine the phase
diagram of an optical many-body system without the need for thermalization.Comment: 4 pages, 4 figure
Search for cosmic gamma radiation with a vidicon spark chamber Final report
Cosmic gamma radiation searched with vidicon spark chamber flown in high-altitude balloo
Role of the target orientation angle and orbital angular momentum in the evaporation residue production
The influence of the orientation angles of the target nucleus symmetry axis
relative to the beam direction on the production of the evaporation residues is
investigated for the Ca+Sm reaction as a function of the beam
energy. At low energies (137 MeV), the yield of evaporation
residues is observed only for collisions with small orientation angles
().
At large energies (about 140--180 MeV) all the orientation
angles can contribute to the evaporation residue cross section
in the 10--100 mb range, and at 180 MeV
ranges around 0.1--10 mb because the fission barrier for a compound nucleus
decreases by increasing its excitation energy and angular momentum.Comment: 20 pages, 10 figures, submitted to JPS
New measurements of the cosmic infrared background fluctuations in deep Spitzer/IRAC survey data and their cosmological implications
We extend previous measurements of cosmic infrared background (CIB)
fluctuations to ~ 1 deg using new data from the Spitzer Extended Deep Survey.
Two fields, with depths of ~12 hr/pixel over 3 epochs, are analyzed at 3.6 and
4.5 mic. Maps of the fields were assembled using a self-calibration method
uniquely suitable for probing faint diffuse backgrounds. Resolved sources were
removed from the maps to a magnitude limit of AB mag ~ 25, as indicated by the
level of the remaining shot noise. The maps were then Fourier-transformed and
their power spectra were evaluated. Instrumental noise was estimated from the
time-differenced data, and subtracting this isolates the spatial fluctuations
of the actual sky. The power spectra of the source-subtracted fields remain
identical (within the observational uncertainties) for the three epochs
indicating that zodiacal light contributes negligibly to the fluctuations.
Comparing to 8 mic power spectra shows that Galactic cirrus cannot account for
the fluctuations. The signal appears isotropically distributed on the sky as
required for an extragalactic origin. The CIB fluctuations continue to diverge
to > 10 times those of known galaxy populations on angular scales out to < 1
deg. The low shot noise levels remaining in the diffuse maps indicate that the
large scale fluctuations arise from the spatial clustering of faint sources
well below the confusion noise. The spatial spectrum of these fluctuations is
in reasonable agreement with an origin in populations clustered according to
the standard cosmological model (LCDM) at epochs coinciding with the first
stars era.Comment: ApJ, to be publishe
Geometrical Defects in Josephson Junction Arrays
Dislocations and disclinations in a lattice of Josephson junctions will
affect the dynamics of vortex excitations within the array. These defects
effectively distort the space in which the excitations move and interact. The
interaction energy between such defects and excitations are determined and
vortex trajectories in twisted lattices are calculated. Finally, possible
experiments observing these effects are presented.Comment: 26 pages including 5 figure
Josephson Vortex Bloch Oscillations: Single Pair Tunneling Effect
We consider the Josephson vortex motion in a long one--dimensional Josephson
junction in a thin film. We show that this Josephson vortex is similar to a
mesoscopic capacitor. We demonstrate that a single Cooper pair tunneling
results in nonlinear Bloch--type oscillations of a Josephson vortex in a
current-biased Josephson junction. We find the frequency and the amplitude of
this motion.Comment: 7 pages, 2 figures included as postscript files, LaTe
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