Heisenberg picture operators in the quantum state diffusion model

A stochastic simulation algorithm for the computation of multitime correlation functions which is based on the quantum state diffusion model of open systems is developed. The crucial point of the proposed scheme is a suitable extension of the quantum master equation to a doubled Hilbert space which is then unraveled by a stochastic differential equation.Comment: LaTeX2E, 6 pages, 3 figures, uses iopar

Transition from diffusive to ballistic dynamics for a class of finite quantum models

The transport of excitation probabilities amongst weakly coupled subunits is investigated for a class of finite quantum systems. It is demonstrated that the dynamical behavior of the transported quantity depends on the considered length scale, e. g., the introduced distinction between diffusive and ballistic transport appears to be a scale-dependent concept, especially since a transition from diffusive to ballistic behavior is found in the limit of small as well as in the limit of large length scales. All these results are derived by an application of the time-convolutionless projection operator technique and are verified by the numerical solution of the full time-dependent Schroedinger equation which is obtained by exact diagonalization for a range of model parameters.Comment: 4 pages, 5 figures, approved for publication in Physical Review Letter

3D simulations of wind-jet interaction in massive X-ray binaries

High-mass microquasars may produce jets that will strongly interact with surrounding stellar winds on binary system spatial scales. We study the dynamics of the collision between a mildly relativistic hydrodynamical jet of supersonic nature and the wind of an OB star. We performed numerical 3D simulations of jets that cross the stellar wind with the code Ratpenat. The jet head generates a strong shock in the wind, and strong recollimation shocks occur due to the initial overpressure of the jet with its environment. These shocks can accelerate particles up to TeV energies and produce gamma-rays. The recollimation shock also strengthens jet asymmetric Kelvin-Helmholtz instabilities produced in the wind/jet contact discontinuity. This can lead to jet disruption even for jet powers of several times $10^{36}$ erg s$^{-1}$. High-mass microquasar jets likely suffer a strong recollimation shock that can be a site of particle acceleration up to very high energies, but also eventually lead to the disruption of the jet.Comment: Accepted for publication in A&A Letter

High temperature color conductivity at next-to-leading log order

The non-Abelian analog of electrical conductivity at high temperature has previously been known only at leading logarithmic order: that is, neglecting effects suppressed only by an inverse logarithm of the gauge coupling. We calculate the first sub-leading correction. This has immediate application to improving, to next-to-leading log order, both effective theories of non-perturbative color dynamics, and calculations of the hot electroweak baryon number violation rate.Comment: 47 pages, 6+2 figure

A DECOMPOSITION APPROACH TO ASSESS ILUC RESULTS FROM GLOBAL MODELING EFFORTS

Environmental Economics and Policy, Resource /Energy Economics and Policy,

Entanglement in SO(3)-invariant bipartite quantum systems

The structure of the state spaces of bipartite (N tensor N) quantum systems which are invariant under product representations of the group SO(3) of three-dimensional proper rotations is analyzed. The subsystems represent particles of arbitrary spin j which transform according to an irreducible representation of the rotation group. A positive map theta is introduced which describes the time reversal symmetry of the local states and which is unitarily equivalent to the transposition of matrices. It is shown that the partial time reversal transformation theta_2 = (I tensor theta) acting on the composite system can be expressed in terms of the invariant 6-j symbols introduced by Wigner into the quantum theory of angular momentum. This fact enables a complete geometrical construction of the manifold of states with positive partial transposition and of the sets of separable and entangled states of (4 tensor 4) systems. The separable states are shown to form a three-dimensional prism and a three-dimensional manifold of bound entangled states is identified. A positive maps is obtained which yields, together with the time reversal, a necessary and sufficient condition for the separability of states of (4 tensor 4) systems. The relations to the reduction criterion and to the recently proposed cross norm criterion for separability are discussed.Comment: 15 pages, 3 figure

Profiling the educational value of computer games

There are currently a number of suggestions for educators to include computer games in formal teaching and learning contexts. Educational value is based on claims that games promote the development of complex learning. Very little research, however, has explored what features should be present in a computer game to make it valuable or conducive to learning. We present a list of required features for an educational game to be of value, informed by two studies, which integrated theories of Learning Environments and Learning Styles. A user survey showed that some requirements were typical of games in a particular genre, while other features were present across all genres. The paper concludes with a proposed framework of games and features within and across genres to assist in the design and selection of games for a given educational scenari

Signatures in a Giant Radio Galaxy of a Cosmological Shock Wave at Intersecting Filaments of Galaxies

Sensitive images of low-level, Mpc-sized radio cocoons offer new opportunities to probe large scale intergalactic gas flows outside clusters of galaxies. New radio images of high surface brightness sensitivity at strategically chosen wavelengths of the giant radio galaxy NGC 315 (Mack et al. 1997,1998) reveal significant asymmetries and particularities in the morphology, radio spectrum and polarization of the ejected radio plasma. We argue that the combination of these signatures provides a sensitive probe of an environmental shock wave. Analysis of optical redshifts in NGC 315 vicinity confirms its location to be near, or at a site of large-scale flow collisions in the 100 Mpc sized Pisces-Perseus Supercluster region. NGC 315 resides at the intersection of several galaxy filaments, and its radio plasma serves there as a `weather station' (Burns 1998) probing the flow of the elusive and previously invisible IGM gas. If our interpretation is correct, this is the first indication for a shock wave in flows caused by the cosmological large scale structure formation, which is located in a filament of galaxies. The possibility that the putative shock wave is a source of gamma-rays and ultra high energy cosmic rays is briefly discussed.Comment: accepted by Astrophysical Journal Letters, 4 pages, 3 figures (incl. 2 color), uses emulateapj5.sty (included), aastex.sty (included) and psfig.st

Generic stability of dissipative non-relativistic and relativistic fluids

The linear stability of the homogeneous equilibrium of non-relativistic fluids with mass flux and special relativistic fluids with the absolute value of the energy vector as internal energy is investigated. It is proved that the equilibrium is asymptotically stable in both cases due to purely thermodynamic restrictions; the only requirements are the thermodynamic stability and the nonnegativity of the transport coefficients.Comment: 22 page