Linear systems solvers - recent developments and implications for lattice computations

We review the numerical analysis' understanding of Krylov subspace methods for solving (non-hermitian) systems of equations and discuss its implications for lattice gauge theory computations using the example of the Wilson fermion matrix. Our thesis is that mature methods like QMR, BiCGStab or restarted GMRES are close to optimal for the Wilson fermion matrix. Consequently, preconditioning appears to be the crucial issue for further improvements.Comment: 7 pages, LaTeX using espcrc2.sty, 2 figures, 9 eps-files, Talk presented at LATTICE96(algorithms), submitted to Nucl. Phys. B, Proc. Supp

Singularities in Speckled Speckle

Speckle patterns produced by random optical fields with two (or more) widely different correlation lengths exhibit speckle spots that are themselves highly speckled. Using computer simulations and analytic theory we present results for the point singularities of speckled speckle fields: optical vortices in scalar (one polarization component) fields; C points in vector (two polarization component) fields. In single correlation length fields both types of singularities tend to be more{}-or{}-less uniformly distributed. In contrast, the singularity structure of speckled speckle is anomalous: for some sets of source parameters vortices and C points tend to form widely separated giant clusters, for other parameter sets these singularities tend to form chains that surround large empty regions. The critical point statistics of speckled speckle is also anomalous. In scalar (vector) single correlation length fields phase (azimuthal) extrema are always outnumbered by vortices (C points). In contrast, in speckled speckle fields, phase extrema can outnumber vortices, and azimuthal extrema can outnumber C points, by factors that can easily exceed $10^{4}$ for experimentally realistic source parameters

Nuclear effects and their interplay in nuclear DVCS amplitudes

In this paper we analyze nuclear medium effects on DVCS amplitudes in the \Bx range of $0.1-0.0001$ for a large range of $Q^2$ and four different nuclei. We use our nucleon GPD model capable of describing all currently available DVCS data on the proton and extend it to the nuclear case using two competing parameterizations of nuclear effects. The two parameterizations, though giving different absolute numbers, yield the same type and magnitude of effects for the imaginary and real part of the nuclear DVCS amplitude. The imaginary part shows stronger nuclear shadowing effects compared to the inclusive case i.e. $F^N_2$, whereas in the real part nuclear shadowing at small \Bx and anti-shadowing at large \Bx combine through evolution to yield an even greater suppression than in the imaginary part up to large values of \Bx. This is the first time that such a combination of nuclear effects has been observed in a hadronic amplitude. The experimental implications will be discussed in a subsequent publication.Comment: 8 pages, 5 figures, uses RevTex4, final version to appear in PHys. Rev.

Medicaid, Managed Care, and Kids. 12th Annual Herbert Lourie Memorial Lecture on Health Policy

This policy brief talks about what managed care for Medicaid is, how it influences kids, and how it relates to the State Child Health Insurance Program (CHIP). It focuses on what we have learned over the last 20 years through research about cost, use, and quality. It also discusses some of the expectations we had for children covered by Medicaid managed care. Finally, it talks abaout the future of Medicaid managed care and the implications for CHIP.

Geometric scaling in inclusive e A reactions and nonlinear perturbative QCD

In this note we report on geometric scaling in inclusive e A scattering data from the NMC and E665 experiments. We show that this scaling, as well as nuclear shadowing, is expected in the framework of nonlinear pQCD at small x based on a simple rescaling argument for e p scattering

The DVCS Measurement at HERA

The recent results of the studies of Deeply Virtual Compton Scattering (DVCS) events at HERA are presented. The possibility offered by this process to gain information about skewed parton distributions (SPD) is emphasized.Comment: Talk given at New Trends in HERA Physics 2001, Ringberg Castle, Tegernsee, Germany, 17-22 Jun 2001, 13 pages, 10 figures, recent ZEUS data discussed, references update

Molecular Dynamics of Comminution in Ball Mills

We investigate autogenous fragmentation of dry granular material in rotating cylinders using two-dimensional molecular dynamics. By evaluation of spatial force distributions achieved numerically for various rotation velocities we argue that comminution occurs mainly due to the existence of force chains. A statistical analysis of theses force chains explains the spatial distribution of comminution efficiency in ball mills as measured experimentally by Rothkegel and Rolf. For animated sequences of our simulations see http://summa.physik.hu-berlin.de/~kies/Research/RotatingCylinder/rotatingcylind er.htmlComment: 15 pages, 13 figure