A Current Microeconometric Assessment of the Racial Wage Gap in the United States

Minority groups in the United States promoted affirmative action legislation in the 1960s during the civil rights movement to help ease the inequalities suffered in their economic history. Many labor economists have sought since this time to study the effects of race, gender, and the effect of income – how it has changed and if the gap has closed. Existing literature uses many different econometric models to show how the effects of race, gender, age, occupation, educational attainment, and geographic location on an individual comparative basis. This paper will examine the effects of all of these variables jointly using an ordinary least squares (OLS) regression analysis. [excerpt

High-frequency dynamics in the near-surface region studied by inelastic x-ray scattering: The case of liquid indium

Inelastic x-ray scattering in grazing angle geometry provides a novel tool for studying the surface and bulk lattice dynamics in a single experiment by varying the incidence angle around the critical angle of total reflection. At very small incidence angles (below the critical angle), it is possible to study the collective dynamics in a subsurface region of a few nanometres at interatomic length and time scales. An experimental study on liquid indium in the near-surface region is presented here and the results are analysed within a theoretical framework, based on classical hydrodynamics for the height-height fluctuations (capillary waves and non-propagating fluctuations) and generalized hydrodynamics for the bulk density fluctuations. The investigation reveals the presence of capillary waves in the inelastic x-ray spectra as an additional contribution at zero-energy transfer and a modification of the bulk density fluctuation contribution. A longer structural relaxation time and a larger longitudinal viscosity with respect to bulk indium are observed, similarly to related studies in confined liquids. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Killing vectors and anisotropy

We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string

Liquid-like behavior of supercritical fluids

The high frequency dynamics of fluid oxygen have been investigated by Inelastic X-ray Scattering. In spite of the markedly supercritical conditions ($T\approx 2 T_c$, $P>10^2 P_c$), the sound velocity exceeds the hydrodynamic value of about 20%, a feature which is the fingerprint of liquid-like dynamics. The comparison of the present results with literature data obtained in several fluids allow us to identify the extrapolation of the liquid vapor-coexistence line in the ($P/P_c$, $T/T_c$) plane as the relevant edge between liquid- and gas-like dynamics. More interestingly, this extrapolation is very close to the non metal-metal transition in hot dense fluids, at pressure and temperature values as obtained by shock wave experiments. This result points to the existence of a connection between structural modifications and transport properties in dense fluids.Comment: 4 pages, 3 figures, accepted by Phys. Rev. Let

High-frequency subsurface and bulk dynamics of liquid indium

We have performed bulk and surface-sensitive inelastic x-ray scattering experiments on liquid indium with 3 meV energy resolution. The experimental data are well reproduced within a generalized hydrodynamic model including structural and microscopic relaxation processes. We find a longitudinal viscosity of 22 mPa s in the near-surface region compared to 7.4 mPa s in the bulk. The origin of the increase is associated with a slowing down of the collective dynamics in a subsurface region of 4.6 nm. © 2007 The American Physical Society

Bond stretching phonon softening and angle-resolved photoemission kinks in optimally doped Bi2Sr1.6La0.4Cu2O6 superconductors

We report the first measurement of the optical phonon dispersion in optimally doped single layer Bi2Sr1.6La0.4Cu2O6+delta using inelastic x-ray scattering. We found a strong softening of the Cu-O bond stretching phonon at about q=(0.25,0,0) from 76 to 60 meV, similar to the one reported in other cuprates. A direct comparison with angle-resolved photoemission spectroscopy measurements taken on the same sample, revealed an excellent agreement in terms of energy and momentum between the ARPES nodal kink and the soft part of the bond stretching phonon. Indeed, we find that the momentum space where a 63 meV kink is observed can be connected with a vector q=(xi,0,0) with xi~0.22, which corresponds exactly to the soft part of the bond stretching phonon mode. This result supports an interpretation of the ARPES kink in terms of electron-phonon coupling.Comment: submited to PR

Solution generating with perfect fluids

We apply a technique, due to Stephani, for generating solutions of the Einstein-perfect fluid equations. This technique is similar to the vacuum solution generating techniques of Ehlers, Harrison, Geroch and others. We start with a ``seed'' solution of the Einstein-perfect fluid equations with a Killing vector. The seed solution must either have (i) a spacelike Killing vector and equation of state P=rho or (ii) a timelike Killing vector and equation of state rho+3P=0. The new solution generated by this technique then has the same Killing vector and the same equation of state. We choose several simple seed solutions with these equations of state and where the Killing vector has no twist. The new solutions are twisting versions of the seed solutions

Understanding the complex phase diagram of uranium: the role of electron-phonon coupling

We report an experimental determination of the dispersion of the soft phonon mode along [1,0,0] in uranium as a function of pressure. The energies of these phonons increase rapidly, with conventional behavior found by 20 GPa, as predicted by recent theory. New calculations demonstrate the strong pressure (and momentum) dependence of the electron-phonon coupling, whereas the Fermi-surface nesting is surprisingly independent of pressure. This allows a full understanding of the complex phase diagram of uranium, and the interplay between the charge-density wave and superconductivity

Velocity and Heat Flow in a Composite Two Fluid System

We describe the stress energy of a fluid with two unequal stresses and heat flow in terms of two perfect fluid components. The description is in terms of the fluid velocity overlap of the components, and makes no assumptions about the equations of state of the perfect fluids. The description is applied to the metrics of a conformally flat system and a black string.Comment: typos correcte