Coupled Ito equations of continuous quantum state measurement, and estimation

We discuss a non-linear stochastic master equation that governs the time-evolution of the estimated quantum state. Its differential evolution corresponds to the infinitesimal updates that depend on the time-continuous measurement of the true quantum state. The new stochastic master equation couples to the two standard stochastic differential equations of time-continuous quantum measurement. For the first time, we can prove that the calculated estimate almost always converges to the true state, also at low-efficiency measurements. We show that our single-state theory can be adapted to weak continuous ensemble measurements as well.Comment: 5 pages, RevTeX4. In version v2 some minor revisions and clarifications have been incorporated. Moreover, a new reference has been included. Accepted for publication in Journal of Physics A: Mathematical and Genera

Coarse-grained description of localized inelastic deformation in amorphous metals

The sequence of shear transformation events that lead to a shear band transition in amorphous metals is described by a spatially random coarse-grained model calibrated to obey the thermodynamic scaling relations that govern flow in a real glass. The model demonstrates that shear banding is a consequence of local shear transformation events that self-organize along planes of maximum resolved shear stress to form extended bands of highly localized deformation. This description suggests that shear band formation is incipient during the early stages of deformation of a randomly inhomogeneous material

Formation of Two Glass Phases in Binary Cu-Ag Liquid

The glass transition is alternatively described as either a dynamic transition in which there is a dramatic slowing down of the kinetics, or as a thermodynamic phase transition. To examine the physical origin of the glass transition in fragile Cu-Ag liquids, we employed molecular dynamics (MD) simulations on systems in the range of 32,000 to 2,048,000 atoms. Surprisingly, we identified a 1st order freezing transition from liquid (L) to metastable heterogenous solid-like phase, denoted as the G-glass, when a supercooled liquid evolves isothermally below its melting temperature at deep undercooling. In contrast, a more homogenous liquid-like glass, denoted as the L-glass, is achieved when the liquid is quenched continuously to room temperature with a fast cooling rate of ∼10¹¹ K/sec. We report a thermodynamic description of the L-G transition and characterize the correlation length of the heterogenous structure in the G-glass. The shear modulus of the G-glass is significantly higher than the L-glass, suggesting that the first order L-G transition is linked fundamentally to long-range elasticity involving elementary configurational excitations in the G-glass

Medium-induced multi-photon radiation

We study the spectrum of multi-photon radiation off a fast quark in medium in the BDMPS/ASW approach. We reproduce the medium-induced one-photon radiation spectrum in dipole approximation, and go on to calculate the two-photon radiation in the Moli\`{e}re limit. We find that in this limit the LPM effect holds for medium-induced two-photon ladder emission.Comment: 5 pages, 1 figure. Proceedings of Hot Quarks 2010, La Londe Les Maures, Franc

The Maximum Optical Depth Towards Bulge Stars From Axisymmetric Models of the Milky Way

It has been known that recent microlensing results towards the bulge imply mass densities that are surprisingly high given dynamical constraints on the Milky Way mass distribution. We derive the maximum optical depth towards the bulge that may be generated by axisymmetric structures in the Milky Way, and show that observations are close to surpassing these limits. This result argues in favor of a bar as a source of significantly enhanced microlensing. Several of the bar models in the literature are discussed.Comment: Latex, 6 pages, 4 figures, uses aas2pp4 and epsf style files. Accepted for publication in ApJ Letter