Pareto's Law of Income Distribution: Evidence for Germany, the United Kingdom, and the United States

We analyze three sets of income data: the US Panel Study of Income Dynamics PSID), the British Household Panel Survey (BHPS), and the German Socio-Economic Panel (GSOEP). It is shown that the empirical income distribution is consistent with a two-parameter lognormal function for the low-middle income group (97%-99% of the population), and with a Pareto or power law function for the high income group (1%-3% of the population). This mixture of two qualitatively different analytical distributions seems stable over the years covered by our data sets, although their parameters significantly change in time. It is also found that the probability density of income growth rates almost has the form of an exponential function.Comment: Latex2e v1.6; 16 pages with 5 figure

Q-stars in extra dimensions

We study q-stars with global and local U(1) symmetry in extra dimensions in asymptotically anti de Sitter or flat spacetime. The behavior of the mass, radius and particle number of the star is quite different in 3 dimensions, but in 5, 6, 8 and 11 dimensions is similar to the behavior in 4.Comment: 18 pages, to appear in Phys. Rev.

Numerical evidence for `multi-scalar stars'

We present a class of general relativistic soliton-like solutions composed of multiple minimally coupled, massive, real scalar fields which interact only through the gravitational field. We describe a two-parameter family of solutions we call ``phase-shifted boson stars'' (parameterized by central density rho_0 and phase delta), which are obtained by solving the ordinary differential equations associated with boson stars and then altering the phase between the real and imaginary parts of the field. These solutions are similar to boson stars as well as the oscillating soliton stars found by Seidel and Suen [E. Seidel and W.M. Suen, Phys. Rev. Lett. 66, 1659 (1991)]; in particular, long-time numerical evolutions suggest that phase-shifted boson stars are stable. Our results indicate that scalar soliton-like solutions are perhaps more generic than has been previously thought.Comment: Revtex. 4 pages with 4 figures. Submitted to Phys. Rev.

Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space

Stability analysis of the Bianchi type I universe in pure gravity theory is studied in details. We first derive the non-redundant field equation of the system by introducing the generalized Bianchi type I metric. This non-redundant equation reduces to the Friedmann equation in the isotropic limit. It is shown further that any unstable mode of the isotropic perturbation with respect to a de Sitter background is also unstable with respect to anisotropic perturbations. Implications to the choice of physical theories are discussed in details in this paper.Comment: 5 pages, some comment adde

Conductivity Due to Classical Phase Fluctuations in a Model For High-T_c Superconductors

We consider the real part of the conductivity, \sigma_1(\omega), arising from classical phase fluctuations in a model for high-T_c superconductors. We show that the frequency integral of that conductivity, \int_0^\infty \sigma_1 d\omega, is non-zero below the superconducting transition temperature $T_c$, provided there is some quenched disorder in the system. Furthermore, for a fixed amount of quenched disorder, this integral at low temperatures is proportional to the zero-temperature superfluid density, in agreement with experiment. We calculate \sigma_1(\omega) explicitly for a model of overdamped phase fluctuations.Comment: 4pages, 2figures, submitted to Phys.Rev.

Functional improvement after one- and two-eye cataract surgery in the salisbury eye evaluation

Purpose: To determine the impact that cataract and cataract surgery have on clinical measurements of vision, reading speed, objective mobility performance, and subjective visual functioning. Design: Prospective, population-based study. Participants: A total of 1739 Salisbury Eye Evaluation (SEE) participants without previous cataract surgery with bilateral baseline best-corrected visual acuity (BCVA) of logarithm of the minimum angle of resolution (logMAR) ≤0.3 (≥20/40) or cataract surgery between rounds 1 and 2. Methods: Participants were categorized on the basis of cataract surgery by round 2 into no surgery, unilateral surgery, or bilateral surgery. Visual performance, mobility-based tasks, and the Activities of Daily Vision Scale (ADVS) were measured at baseline and 2 years. Mobility score was converted into a z score by subtracting the participant's time from the population baseline average and then dividing by the standard deviation. Comparisons were made between the no surgery and surgery groups using multivariate linear regression. Main Outcome Measures: Change in bilateral BCVA in logMAR, contrast sensitivity, reading speed in words per minute (wpm), mobility score, and ADVS. Results: During the study period, 29 participants had cataract surgery on both eyes, 90 participants had unilateral surgery, and 1620 participants had no surgery. After adjusting for baseline value, demographics, depression, and mental status, the unilateral surgery group's BCVA improved 0.04 logMAR (P = 0.001) and the bilateral group's BCVA improved 0.13 compared with no surgery (P<0.001). Overall mobility declined in all groups. The unilateral group's z score decreased 0.18 more than that of the no surgery group (P = 0.02), whereas the bilateral group showed a 0.18 z score improvement compared with no surgery (P = 0.19). Change in reading speed significantly improved in the unilateral and bilateral groups compared with no surgery (12 and 31 wpm, respectively). The bilateral surgery group showed significant positive change in ADVS compared with no surgery (5 points of relative improvement; P = 0.01), whereas the unilateral group showed a 5-point relative decline (P<0.001). Conclusions: Cataract negatively affects both subjective quality of life and objective performance measures. Unilateral cataract surgery improves visual functioning, but the largest gains are found in patients who undergo second-eye cataract surgery. This finding supports second-eye cataract surgery for patients with visual or functional symptoms even after successful first-eye surgery

The low-energy phase-only action in a superconductor: a comparison with the XY model

The derivation of the effective theory for the phase degrees of freedom in a superconductor is still, to some extent, an open issue. It is commonly assumed that the classical XY model and its quantum generalizations can be exploited as effective phase-only models. In the quantum regime, however, this assumption leads to spurious results, such as the violation of the Galilean invariance in the continuum model. Starting from a general microscopic model, in this paper we explicitly derive the effective low-energy theory for the phase, up to fourth-order terms. This expansion allows us to properly take into account dynamic effects beyond the Gaussian level, both in the continuum and in the lattice model. After evaluating the one-loop correction to the superfluid density we critically discuss the qualitative and quantitative differences between the results obtained within the quantum XY model and within the correct low-energy theory, both in the case of s-wave and d-wave symmetry of the superconducting order parameter. Specifically, we find dynamic anharmonic vertices, which are absent in the quantum XY model, and are crucial to restore Galilean invariance in the continuum model. As far as the more realistic lattice model is concerned, in the weak-to-intermediate-coupling regime we find that the phase-fluctuation effects are quantitatively reduced with respect to the XY model. On the other hand, in the strong-coupling regime we show that the correspondence between the microscopically derived action and the quantum XY model is recovered, except for the low-density regime.Comment: 29 pages, 11 figures. Slightly revised presentation, accepted for publication in Phys. Rev.

Friedmann Equation and Stability of Inflationary Higher Derivative Gravity

Stability analysis on the De Sitter universe in pure gravity theory is known to be useful in many aspects. We first show how to complete the proof of an earlier argument based on a redundant field equation. It is shown further that the stability condition applies to $k \ne 0$ Friedmann-Robertson-Walker spaces based on the non-redundant Friedmann equation derived from a simple effective Lagrangian. We show how to derive this expression for the Friedmann equation of pure gravity theory. This expression is also generalized to include scalar field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte

Avoiding degenerate coframes in an affine gauge approach to quantum gravity

In quantum models of gravity, it is surmized that configurations with degenerate coframes could occur during topology change of the underlying spacetime structure. However, the coframe is not the true Yang--Mills type gauge field of the translations, since it lacks the inhomogeneous gradient term in the gauge transformations. By explicitly restoring this ``hidden" piece within the framework of the affine gauge approach to gravity, one can avoid the metric or coframe degeneracy which would otherwise interfere with the integrations within the path integral. This is an important advantage for quantization.Comment: 14 pages, Preprint Cologne-thp-1993-H

Models for Enhanced Absorption in Inhomogeneous Superconductors

We discuss the low-frequency absorption arising from quenched inhomogeneity in the superfluid density rho_s of a model superconductor. Such inhomogeneities may arise in a high-T_c superconductor from a wide variety of sources, including quenched random disorder and static charge density waves such as stripes. Using standard classical methods for treating randomly inhomogeneous media, we show that both mechanisms produce additional absorption at finite frequencies. For a two-fluid model with weak mean-square fluctuations <(d rho_s)^2 > in rho_s and a frequency-independent quasiparticle conductivity, the extra absorption has oscillator strength proportional to the quantity <(d rho_s)^2>/rho_s, as observed in some experiments. Similar behavior is found in a two-fluid model with anticorrelated fluctuations in the superfluid and normal fluid densities. The extra absorption typically occurs as a Lorentzian centered at zero frequency. We present simple model calculations for this extra absorption under conditions of both weak and strong fluctuations. The relation between our results and other model calculations is briefly discussed