Criticality and entanglement in random quantum systems

We review studies of entanglement entropy in systems with quenched randomness, concentrating on universal behavior at strongly random quantum critical points. The disorder-averaged entanglement entropy provides insight into the quantum criticality of these systems and an understanding of their relationship to non-random ("pure") quantum criticality. The entanglement near many such critical points in one dimension shows a logarithmic divergence in subsystem size, similar to that in the pure case but with a different universal coefficient. Such universal coefficients are examples of universal critical amplitudes in a random system. Possible measurements are reviewed along with the one-particle entanglement scaling at certain Anderson localization transitions. We also comment briefly on higher dimensions and challenges for the future.Comment: Review article for the special issue "Entanglement entropy in extended systems" in J. Phys.

How Beliefs about HIV Status Affect Risky Behaviors: Evidence from Malawi, Fifth Version

This paper examines how beliefs about own HIV status affect decisions to engage in risky sexual behavior using data on married males living in Malawi. Risky behavior is measured as the propensity to engage in extramarital affairs. The empirical analysis is based on panel surveys for years 2006 and 2008 from the Malawi Diffusion and Ideational Change Project (MDICP). Beliefs vary significantly over time in the data, in part because of HIV testing and informational campaigns. We estimate the effect of beliefs about own HIV status on risky behavior using a panel data estimator developed by Arellano and Carrasco (2003), which accommodates unobserved heterogeneity as well as belief endogeneity arising from the dependence of current beliefs on lagged behaviors. We find that beliefs are an important determinant of risky behavior, with downward revisions in the belief of being HIV positive increasing risky behavior and upward revisions decreasing it. We modify Arellano and Carrasco’s (2003) estimator to allow for underreporting of affairs and find the estimates to be relatively robust to underreporting. Using our estimates and a prototypical epidemiological model of disease transmission, we show that making individuals better informed about their HIV status, either by increasing the credibility of test results and/or increasing access to testing, would on net reduce the HIV transmission rate.Beliefs, Malawi, HIV

Near-field EM wave scattering from random self-affine fractal metal surfaces: spectral dependence of local field enhancements and their statistics in connection with SERS

By means of rigorous numerical simulation calculations based on the Green's theorem integral equation formulation, we study the near EM field in the vicinity of very rough, one-dimensional self-affine fractal surfaces of Ag, Au, and Cu (for both vacuum and water propagating media) illuminated by a p polarized field. Strongly localized enhanced optical excitations (hot spots) are found, with electric field intensity enhancements of close to 4 orders of magnitude the incident one, and widths below a tenth of the incoming wavelength. These effects are produced by roughness-induced surface-plasmon polariton excitation. We study the characteristics of these optical excitations as well as other properties of the surface electromagnetic field, such as its statistics (probability density function, average and fluctuations), and their dependence on the excitation spectrum (in the visible and near infrared). Our study is relevant to the use of such self-affine fractals as surface-enhanced Raman scattering substrates, where large local and average field enhancements are desired.Comment: REVTeX 3.1, 11 pages with 10 EPS figures (epsf macro

The determinants of changes in the organization of production: Evidence from Spanish plant-level data

In this paper we empirically examine the determinants of changes in the organization of production using detailed information on a data set from a new plant-level survey of 1003 plants covering the full range of manufacturing industries in Spain. In particular, and among many other things, survey respondents were asked how service outsourcing practices had changed in the last three years. The answer to this question is indicative of the changes in the importance of backward integration for each of the plants studied. Using other information provided in the survey, we relate the reported changes in outsourcing to changes in other relevant dimensions as possible determinants of the boundaries of the firm. These dimensions are: plant size, downstream market power, cost of inputs, price and quality of the final good and technological progress. Our findings show that outsourcing increases are strongly positively correlated with increases in market share and in market competition. We also find that outsourcing increases when plants face simultaneous increases in product quality and product prices and that it decreases when plants face simultaneous increases in market share and market competition. Finally, we find that multi-plant and one-plant firms adjust their outsourcing practices differently to outside changes. Since neither TCE nor PRT theories of vertical integration fully explain the patterns found in our data, we close this paper by following Adam Smith's claim that the extent of the market seems to be the only factor consistently limiting the degree of specialization in our setting.outsourcing; vertical integration; competition; manufacturing plants;

Superconductivity of doped Weyl semimetals: finite-momentum pairing and electronic analogues of the 3He-A phase

We study superconducting states of doped inversion-symmetric Weyl semimetals. Specifically, we consider a lattice model realizing a Weyl semimetal with an inversion symmetry and study the superconducting instability in the presence of a short-ranged attractive interaction. With a phonon-mediated attractive interaction, we find two competing states: a fully gapped finite-momentum (FFLO) pairing state and a nodal even-parity pairing state. We show that, in a BCS-type approximation, the finite-momentum pairing state is energetically favored over the usual even-parity paired state and is robust against weak disorder. Though energetically unfavorable, the even-parity pairing state provides an electronic analogue of the 3He-A phase in that the nodes of the even-parity state carry non-trivial winding numbers and therefore support a surface flat band. We briefly discuss other possible superconducting states that may be realized in Weyl semimetals.Comment: 9 pages, 2 tables, 2 figures. references are updated and the discussion on the half-qauntum and full-quantum vortices is adde

Reform in California\u27s Immigration Enforcement and Immigration Court

According to the Department of Homeland Security, Office of Immigration Statistic, California accounts for approximately 2,600,000 illegal immigrants in 2009. This number represents about 25 percent of the entire estimated illegal immigrant population in the United States, which is roughly 10.8 million. Between 2003 and 2008, the U.S. government removed 1,446,338 noncitizens from the United States. This rise in deportation is a result o the changes that have been enacted by the federal government over the years that transformed the nature of immigration enforcement. This thesis explores the California Immigration Enforcement system from the programs established to apprehend illegal aliens in the United States, the rights illegal aliens are granted, the detention facilities where they reside and the immigration courts that ultimately decide their fate. The question that is being asked is whether the current system established works or if reform is needed