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

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

DVCS on nuclei: Observability and Consequences

In this paper, we discuss the feasibility of measuring deeply virtual Compton scattering (DVCS) on nuclei in a collider setting, as for example, the planned high-luminosity Electron-Ion-Collider (EIC). We demonstrate that employing our recent model for nuclear generalized parton distributions (nGPDs), the one-photon unpolarized DVCS cross section as well as the azimuthal- and spin asymmetry are of the same size as in the proton case. This will allow for an experimental extraction of nuclear GPDs with high precision shedding new light on nuclear shadowing at small $x_{bj}$ and the interplay of shadowing and nuclear enhancement at $x_{bj}~0.1$.Comment: 9 pages, 18 figures, uses EPJ style format, final version to appear in EPJ

Single spin asymmetry in DVCS

In the following note, we will present an estimation of the single spin asymmetry in deeply virtual Compton scattering (DVCS) which directly allows one to test predictions of the ratio of the imaginary part of the amplitude in DIS to DVCS, as well as access the skewed parton distributions at small $x$ in the DGLAP region. We find it to be large for the HERA kinematics to be accessible in forthcoming runs with polarized electrons.Comment: 6 pages, 2 figures in eps format. Submitted to Phys. Rev. D's Rapid Communication

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.