Numerical methods for incompressible viscous flows with engineering applications

A numerical scheme has been developed to solve the incompressible, 3-D Navier-Stokes equations using velocity-vorticity variables. This report summarizes the development of the numerical approximation schemes for the divergence and curl of the velocity vector fields and the development of compact schemes for handling boundary and initial boundary value problems

Deterministic Annealing as a jet clustering algorithm in hadronic collisions

We show that a general purpose clusterization algorithm, Deterministic Annealing, can be adapted to the problem of jet identification in particle production by high energy collisions. In particular we consider the problem of jet searching in events generated at hadronic colliders. Deterministic Annealing is able to reproduce the results obtained by traditional jet algorithms and to exhibit a higher degree of flexibility.Comment: 13 pages, 6 figure

Interpretation of x-ray-absorption dichroism experiments

A rule is derived to use x-ray magnetic circular dichroism spectra to extract the magnetic moment of the conduction-band states with j= l -1/2 separately from those with j= l + 1/2 as a function of energy. This quantity is straightforward to determine from the electronic band structure. The rule is illustrated with an application to pure iron and to the random substitutional alloy Fe_{80}CO_{20}

Giant electrocaloric effect around Tc_c

We use molecular dynamics with a first-principles-based shell model potential to study the electrocaloric effect (ECE) in lithium niobate, LiNbO$_3$, and find a giant electrocaloric effect along a line passing through the ferroelectric transition. With applied electric field, a line of maximum ECE passes through the zero field ferroelectric transition, continuing along a Widom line at high temperatures with increasing field, and along the instability that leads to homogeneous ferroelectric switching below $T_c$ with an applied field antiparallel to the spontaneous polarization. This line is defined as the minimum in the inverse capacitance under applied electric field. We investigate the effects of pressure, temperature and applied electric field on the ECE. The behavior we observe in LiNbO$_3$ should generally apply to ferroelectrics; we therefore suggest that the operating temperature for refrigeration and energy scavenging applications should be above the ferroelectric transition region to obtain large electrocaloric response. We find a relationship among $T_c$, the Widom line and homogeneous switching that should be universal among ferroelectrics, relaxors, multiferroics, and the same behavior should be found under applied magnetic fields in ferromagnets.Comment: 5 page

Limits on entanglement in rotationally-invariant scattering of spin systems

This paper investigates the dynamical generation of entanglement in scattering systems, in particular two spin systems that interact via rotationally-invariant scattering. The spin degrees of freedom of the in-states are assumed to be in unentangled, pure states, as defined by the entropy of entanglement. Because of the restriction of rotationally-symmetric interactions, perfectly-entangling S-matrices, i.e. those that lead to a maximally entangled out-state, only exist for a certain class of separable in-states. Using Clebsch-Gordan coefficients for the rotation group, the scattering phases that determine the S-matrix are determined for the case of spin systems with $\sigma = 1/2$, 1, and 3/2.Comment: 6 pages, no figures; v.2: sections added, edited for clarity, conclusions and calculation unchanged, typos corrected; v.3: new abstrct, revised first two sections, added reference

Comment on "Fisheries Management"

The recent article by O’Leary et al. (2011) raises an important question about the relationship between science and those who manage fisheries. They contend that fishery managers do not give due cognisance to scientific advice and consistently set Total Allowable Catches (TACs) above values advised by scientists (which they define as ‘‘political adjustment’’). The authors claim that the consequence of this is that there is a high probability of stock collapse in the next 40 years. They use a simulation model to argue that this probability may exceed 80% at the mean level of political adjustment adopted by managers, depending on the degree of environmental variability and life history strategy of the fish