Two interacting atoms in a cavity: exact solutions, entanglement and decoherence

We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalues and eigenfunctions using a new invariant. This model encompasses various commonly used models. By way of example we obtain closed expressions for concurrence and purity as a function of time for the case where the cavity is prepared in a number state. We discuss the behaviour of these quantities and and their relative behaviour in the concurrence-purity plane.Comment: 10 pages, 3 figure

Decoherence at constant excitation

We present a simple exactly solvable extension of of the Jaynes-Cummings model by adding dissipation. This is done such that the total number of excitations is conserved. The Liouville operator in the resulting master equation can be reduced to blocks of $4\times 4$ matrices

A random matrix approach to decoherence

In order to analyze the effect of chaos or order on the rate of decoherence in a subsystem, we aim to distinguish effects of the two types of dynamics by choosing initial states as random product states from two factor spaces representing two subsystems. We introduce a random matrix model that permits to vary the coupling strength between the subsystems. The case of strong coupling is analyzed in detail, and we find no significant differences except for very low-dimensional spaces.Comment: 11 pages, 5 eps-figure

Preventing adolescents’ externalizing and internalizing symptoms : effects of the Penn Resiliency Program

This study reports secondary outcome analyses from a past study of the Penn Resiliency Program (PRP), a cognitive-behavioral depression prevention program for middle-school aged children. Middle school students (N = 697) were randomly assigned to PRP, PEP (an alternate intervention), or control conditions. Gillham et al., (2007) reported analyses examining PRP’s effects on average and clinical levels of depression symptoms. We examine PRP’s effects on parent-, teacher-, and self-reports of adolescents’ externalizing and broader internalizing (depression/anxiety, somatic complaints, and social withdrawal) symptoms over three years of follow-up. Relative to no intervention control, PRP reduced parent-reports of adolescents’ internalizing symptoms beginning at the first assessment after the intervention and persisting for most of the follow-up assessments. PRP also reduced parent-reported conduct problems relative to no-intervention. There was no evidence that the PRP program produced an effect on teacher- or self-report of adolescents’ symptoms. Overall, PRP did not reduce symptoms relative to the alternate intervention, although there is a suggestion of a delayed effect for conduct problems. These findings are discussed with attention to developmental trajectories and the importance of interventions that address common risk factors for diverse forms of negative outcomes.peer-reviewe

Spectral sum rules and finite volume partition function in gauge theories with real and pseudoreal fermions

Based on the chiral symmetry breaking pattern and the corresponding low-energy effective lagrangian, we determine the fermion mass dependence of the partition function and derive sum rules for eigenvalues of the QCD Dirac operator in finite Euclidean volume. Results are given for $N_c = 2$ and for Yang-Mills theory coupled to several light adjoint Majorana fermions. They coincide with those derived earlier in the framework of random matrix theory.Comment: 22p., SUNY-NTG-94/18, TPI-MINN-94/10-

Fidelity amplitude of the scattering matrix in microwave cavities

The concept of fidelity decay is discussed from the point of view of the scattering matrix, and the scattering fidelity is introduced as the parametric cross-correlation of a given S-matrix element, taken in the time domain, normalized by the corresponding autocorrelation function. We show that for chaotic systems, this quantity represents the usual fidelity amplitude, if appropriate ensemble and/or energy averages are taken. We present a microwave experiment where the scattering fidelity is measured for an ensemble of chaotic systems. The results are in excellent agreement with random matrix theory for the standard fidelity amplitude. The only parameter, namely the perturbation strength could be determined independently from level dynamics of the system, thus providing a parameter free agreement between theory and experiment

Relativistic echo dynamics and the stability of a beam of Landau electrons

We extend the concepts of echo dynamics and fidelity decay to relativistic quantum mechanics, specifically in the context of Klein-Gordon and Dirac equations under external electromagnetic fields. In both cases we define similar expressions for the fidelity amplitude under perturbations of these fields, and a covariant version of the echo operator. Transformation properties under the Lorentz group are established. An alternate expression for fidelity is given in the Dirac case in terms of a 4-current. As an application we study a beam of Landau electrons perturbed by field inhomogeneities.Comment: 8 pages, no figure

Removal processes for tributyltin during municipal wastewater treatment

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2013 Springer.The fate and behaviour of tributyltin (TBT) at two wastewater treatment works was examined. Both sites had two inlet streams, and each utilised high rate biological filters (biofilters) on one the streams, before treatment of the combined flows on trickling filters, with one having additional tertiary processes, installed to remove ammonia and solids. The study was designed to determine if these processes enhanced the removal of TBT. Degradation of TBT was observed in one of the biofilters, possibly as a result of temperature and hydraulic loading. At the treatment works with tertiary processes, the mass flux showed the overall removal of TBT was 68 %, predominantly due to removal with solids in the primary settlement processes. However, overall removal of 95 % was observed in the conventional trickling filter works with 94 % of this due to biodegradation in the trickling filter. The two works both removed TBT, but at different treatment stages and by different processes. Differences in the form (solubility) of TBT in the influent may have attributed to this, although further understanding of factors controlling degradation would allow for a more complete assessment of the potential of biological processes to remove hazardous compounds from wastewaters.United Utilities PL