The effect of short ray trajectories on the scattering statistics of wave chaotic systems

In many situations, the statistical properties of wave systems with chaotic classical limits are well-described by random matrix theory. However, applications of random matrix theory to scattering problems require introduction of system specific information into the statistical model, such as the introduction of the average scattering matrix in the Poisson kernel. Here it is shown that the average impedance matrix, which also characterizes the system-specific properties, can be expressed in terms of classical trajectories that travel between ports and thus can be calculated semiclassically. Theoretical results are compared with numerical solutions for a model wave-chaotic system

Inducing Barbero-Immirzi Connections along SU(2)-reductions of Bundles on Spacetime

We shall present here a general apt technique to induce connections along bundle reductions which is different from the standard restriction. This clarifies and generalizes the standard procedure to define Barbero-Immirzi (BI) connection, though on spacetime. The standard spacial BI connection used in LQG is then obtained by its spacetime version by standard restriction. The general prescription to define such a reduced connection is interesting from a mathematical viewpoint and it allows a general and direct control on transformation laws of the induced object. Moreover, unlike what happens by using standard restriction, we shall show that once a bundle reduction is given, then any connection induces a reduced connection with no constraint on the original holonomy as it happens when connections are simply restricted.Comment: 6 pages, some comments adde

Quantum chaos of a mixed, open system of kicked cold atoms

The quantum and classical dynamics of particles kicked by a gaussian attractive potential are studied. Classically, it is an open mixed system (the motion in some parts of the phase space is chaotic, and in some parts it is regular). The fidelity (Lochshmidt echo) is found to exhibit oscillations that can be determined from classical considerations but are sensitive to phase space structures that are smaller than Planck's constant. Families of quasi-energies are determined from classical phase space structures. Substantial differences between the classical and quantum dynamics are found for time dependent scattering. It is argued that the system can be experimentally realized by cold atoms kicked by a gaussian light beam.Comment: 19 pages, 21 figures, (accepted for publication in Phys. Rev. E

Universal Statistics of the Scattering Coefficient of Chaotic Microwave Cavities

We consider the statistics of the scattering coefficient S of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental S data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized, complex scattering coefficient whose Probability Density Function (PDF) is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We compare experimental PDFs of the normalized scattering coefficients with those obtained from Random Matrix Theory (RMT), and find excellent agreement. The results apply to scattering measurements on any wave chaotic system.Comment: 10 pages, 8 Figures, Fig.7 in Color, Submitted to Phys. Rev.

Characterization of Fluctuations of Impedance and Scattering Matrices in Wave Chaotic Scattering

In wave chaotic scattering, statistical fluctuations of the scattering matrix $S$ and the impedance matrix $Z$ depend both on universal properties and on nonuniversal details of how the scatterer is coupled to external channels. This paper considers the impedance and scattering variance ratios, $VR_z$ and $VR_s$, where $VR_z=Var[Z_{ij}]/\{Var[Z_{ii}]Var[Z_{jj}] \}^{1/2}$, $VR_s=Var[S_{ij}]/\{Var[S_{ii}]Var[S_{jj}] \}^{1/2}$, and $Var[.]$ denotes variance. $VR_z$ is shown to be a universal function of distributed losses within the scatterer. That is, $VR_z$ is independent of nonuniversal coupling details. This contrasts with $VR_s$ for which universality applies only in the large loss limit. Explicit results are given for $VR_z$ for time reversal symmetric and broken time reversal symmetric systems. Experimental tests of the theory are presented using data taken from scattering measurements on a chaotic microwave cavity.Comment: 6 pages, 5 figures, updated with referees' comment

Casimir Effect for Spherical Shell in de Sitter Space

The Casimir stress on a spherical shell in de Sitter background for massless scalar field satisfying Dirichlet boundary conditions on the shell is calculated. The metric is written in conformally flat form. Although the metric is time dependent no particles are created. The Casimir stress is calculated for inside and outside of the shell with different backgrounds corresponding to different cosmological constants. The detail dynamics of the bubble depends on different parameter of the model. Specifically, bubbles with true vacuum inside expand if the difference in the vacuum energies is small, otherwise they collapse.Comment: 9 pages, submitted to Class. Quantum Gra

Propellant Charring in Pulsed Plasma Thrusters

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76437/1/AIAA-2471-899.pd