Random Classical Fidelity

We introduce a random perturbed version of the classical fidelity and we show that it converges with the same rate of decay of correlations, but not uniformly in the noise. This makes the classical fidelity unstable in the zero-noise limit.     

The Systematics of Muonium Hyperfine Constants

The hyperfine constants for muonium in elemental and binary inorganic solids suggest formation of three different families of defect centre, with distinct electronic structures. The overall range of values, spanning nearly five orders of magnitude, and their correlation with host properties such as band gap and electron affinity, reveal a deep-to-shallow instability which has profound implications for the electrical properties of hydrogen impurity in electronic materials, both semiconducting and dielectric.     

Creating, detecting and locating ultracold molecules in a surface trap

Ultracold molecules have been produced by photoassociation of Cs atoms trapped in a mirror magneto-optical trap. The molecules were detected by resonantly enhanced multi-photon ionization followed by time-of-flight mass spectroscopy. The time-of-flight ofatomic and molecular ions was investigated in the presence of a dc bias voltageapplied to the conducting mirror. This technique provides a new tool for determining the distance between the cold molecules and the mirror surface. This revised version was published online in August 2005 with a corrected cover date.     

Microlocal analysis of seismic inverse scattering in anisotropic elastic media

Seismic data is modeled in the high‐frequency approximation, using the techniques of microlocal analysis. We consider general, anisotropic elastic media. Our methods are designed to allow for the formation of caustics. The data is modeled in two ways. First, we give a microlocal treatment of the Kirchhoff approximation, where the medium is assumed to be piecewise smooth, and reflection and transmission occur at interfaces. Second, we give a refined view on the Born approximation based upon a linearization of the scattering process in the medium parameters around a smooth background medium. The joint formulation of Born and Kirchhoff scattering allows us to take into account general scatterers as well as the nonlinear dependence of reflection coefficients on the medium parameters. The latter allows the treatment of scattering up to grazing angles. The outcome of the analysis is a characterization of the singular part of seismic data. We obtain a set of pseudodifferential operators that annihilate the data. In the process we construct a Fourier integral operator and a reflectivity function such that the data can be represented by this operator acting on the reflectivity function. In our construction this Fourier integral operator becomes invertible. We give the conditions for invertibility for general acquisition geometry. The result is also of interest for inverse scattering in acoustic media. © 2002 John Wiley & Sons, Inc.     

A datalogger to identify vocalizing dolphins

A datalogger was developed to identify vocalizing dolphins within socially interacting captive groups. Every 50 ms the logger stores data on the level and frequency of detected sound. Dataloggers are temporarily attached to dolphins by suction cups for data collection sessions lasting up to 45 min. Later, computer analysis of data from the dataloggers reveals which dolphin produced each vocalization recorded during the session. Results from use of dataloggers with two captive bottlenose dolphins (Tursiops truncatus) at the New England Aquarium in Boston, MA are presented. The possible use of dataloggers with wild dolphins is discussed.     

Symmetries of space-time,conservation laws and forbidden motion i: General discussion

The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed.     

Adaptive local grid refinement algorithms for finite-element collocation

An adaptive grid refinement procedure allows accurate solutions to advection-dominated, time-dependent flows using finite-element collocation. The technique relies on a data structure that is readily amenable to parallel computing. The paper discusses computational aspects of the method.     

Asymptotic expansion of the logistic midrange

Using the symbolic computation program MAPLE, we compute several terms of an asymptotic expansion for the distribution function of the logistic midrange.