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 $^{48}$Ca+$^{154}$Sm reaction as a function of the beam energy. At low energies ($E_{\rm c.m.}<$137 MeV), the yield of evaporation residues is observed only for collisions with small orientation angles ($\alpha_T<45^0$). At large energies (about $E_{\rm c.m.}=$140--180 MeV) all the orientation angles $\alpha_T$ can contribute to the evaporation residue cross section $\sigma_{ER}$ in the 10--100 mb range, and at $E_{c.m.}>$180 MeV $\sigma_{ER}$ 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