Imaging of quantum Hall states in ultracold atomic gases

We examine off-resonant light scattering from ultracold atoms in the quantum Hall regime. When the light scattering is spin dependent, we show that images formed in the far field can be used to distinguish states of the system. The spatial dependence of the far-field images is determined by the two-particle spin-correlation functions, which the images are related to by a transformation. Quasiholes in the system appear in images of the density formed by collecting the scattered light with a microscope, where the quasihole statistics are revealed by the reduction in density at the quasihole position

Efficient Estimation of Conditional Asset Pricing Models

A semiparametric efficient estimation procedure is developed for the parameters of multivariate GARCH-in-mean models when the disturbances have a distribution that is assumed to be elliptically symmetric but is otherwise unrestricted. Under high level restrictions, the resulting estimator achieves the asymptotic semiparametric efficiency bound. The elliptical symmetry assumption allows us to avert the curse of dimensionality problem that would otherwise arise in estimating the unknown error distribution. This framework is suitable for the estimation and testing of conditional asset pricing models such as the conditional CAPM, and we apply our estimator in an empirical study of stock prices, with Monte Carlo simulation results also being reported. Nous développons un nouvel estimateur pour les paramètres d'un modèle de GARCH en moyenne (" GARCH-M ") avec plusieurs variables. L'estimateur a l'efficacité semiparamétrique quand les erreurs suivent une loi de probabilité qui est elliptiquement symétrique mais n'aucune autre restriction. Sous les hypothèses de haut niveau, notre estimateur obtient la limite d'efficacité semiparamétrique. L'hypothèse de la symétrie elliptique nous permet d'éviter le problème d'estimer non-paramétriquement une fonction de haut dimension, parce qu'on peut écrire la densité d'un loi elliptique comme un fonction d'une transformation unidimensionnelle de la variable aléatoire multidimensionnelle. Ce cadre est approprié pour analyser des modèles conditionnels des prix des actifs financiers, comme le CAPM conditionnel. Nous appliquons notre méthodologie à l'étude des prix des actions, et nous rendons compte des résultats d'une étude simulation "Monte-Carlo".Capital asset pricing model, elliptical symmetry, semiparametric efficiency, GARCH.

Quantum imaging of spin states in optical lattices

We investigate imaging of the spatial spin distribution of atoms in optical lattices using non-resonant light scattering. We demonstrate how scattering spatially correlated light from the atoms can result in spin state images with enhanced spatial resolution. Furthermore, we show how using spatially correlated light can lead to direct measurement of the spatial correlations of the atomic spin distribution

Testing the Capital Asset Pricing Model Efficiently Under Elliptical Symmetry: A Semiparametric Approach

We develop new tests of the capital asset pricing model (CAPM) that take account of and are valid under the assumption that the distribution generating returns is elliptically symmetric; this assumption is necessary and sufficient for the validity of the CAPM. Our test is based on semiparametric efficient estimation procedures for a seemingly unrelated regression model where the multivariate error density is elliptically symmetric, but otherwise unrestricted. The elliptical symmetry assumption allows us to avert the curse of dimensionality problem that typically arises in multivariate semiparametric estimation procedures, because the multivariate elliptically symmetric density function can be written as a function of a scalar transformation of the observed multivariate data. The elliptically symmetric family includes a number of thick-tailed distributions and so is potentially relevant in financial applications. Our estimated betas are lower than the OLS estimates, and our parameter estimates are much less consistent with the CAPM restrictions than the corresponding OLS estimates. Nous développons de nouveaux tests du modèle d'évaluation des actifs financiers (" CAPM ") qui tiennent compte de, et sont valides sous, l'hypothèse que les retours des actifs découlent d'un loi de probabilité elliptiquement symétrique. Cette hypothèse est nécessaire et suffisante pour la validité du CAPM. Notre test utilise un estimateur des paramètres du modèle qui a l'efficacité semiparamétrique quand on a un modèle de régression apparemment sans relation et qui a des erreurs qui suivent une loi elliptiquement symétrique. L'hypothèse de la symétrie elliptique nous permet d'éviter le problème d'estimer non-paramétriquement une fonction de haute dimension parce qu'on peut écrire la densité d'une loi elliptique comme une fonction d'une transformation unidimensionnelle de la variable aléatoire multidimensionnelle. La famille des lois elliptiquement symétriques inclue plusieurs lois leptokurtiques, donc elle est pertinente à des applications financières. Les bêtas obtenus avec notre estimateur sont plus bas que ceux qui sont obtenus en utilisant des moindres carrés, et sont moins compatibles avec le CAPM.Adaptive estimation, capital asset pricing model, elliptical symmetry, semiparametric efficiency

Secret Spending in the States

Six years after Citizens United enabled unfettered spending in our elections, the use of so-called dark money has become disturbingly common. Contrary to the Supreme Court's assumption that this unlimited spending would be transparent to voters, at the federal level powerful groups have since 2010 poured hundreds of millions of dollars into influencing elections while obscuring the sources of their funding. But it is at the state and local levels that secret spending is arguably at its most damaging. For a clear understanding of the degree to which dark money is warping American democracy, state ballot referenda and local school board contests may be a better starting point than the presidential campaign or even congressional races. As Chris Herstam, a former Republican majority whip in the Arizona House of Representatives and now lobbyist, put it, "In my 33 years in Arizona politics and government, dark money is the most corrupting influence I have seen."This report documents how far outside spending -- election spending that is not coordinated with candidates -- at the state and local levels has veered from the vision of democratic transparency the Citizens United Court imagined, drawing on an extensive database of news accounts, interviews with a range of stakeholders, campaign finance and tax records, court cases, and social science research. For the first time, it also measures changes in dark money – and a thus far unrecognized rise in what we term "gray money" – at the state level, by analyzing spender and contributor reports in six of nine states where sufficient usable data were available. This set of six geographically and demographically diverse states, comprising Alaska, Arizona, California, Colorado, Maine, and Massachusetts, represents approximately 20 percent of the nation's population.

Real and Perceived Losses from Unemployment : a cross-country study

Peer reviewe

Conformal gravity rotation curves with a conformal Higgs halo

We discuss the effect of a conformally coupled Higgs field on Conformal Gravity (CG) predictions for the rotation curves of galaxies. The Mannheim-Kazanas (MK) metric is a valid vacuum solution of CG's 4-th order Poisson equation if and only if the Higgs field has a particular radial profile, S(r) = S0 a/(r + a), decreasing from S0 at r = 0 with radial scale length a. Since particle rest masses scale with S(r)/S0, their world lines do not follow time-like geodesics of the MK metric gμν, as previously assumed, but rather those of the Higgs-frame MK metric ḡμν = Ω2 gμν, with the conformal factor Ω(r) = S(r)/S0. We show that the required stretching of the MK metric exactly cancels the linear potential that has been invoked to fit galaxy rotation curves without dark matter. We also formulate, for spherical structures with a Higgs halo S(r), the CG equations that must be solved for viable astrophysical tests of CG using galaxy and cluster dynamics and lensing.Publisher PDFPeer reviewe

Congressional Roll Call Voting Strategies: Application of a New Test to Minimum Wage Legislation

[No abstract

The Analysis of Committee Power: An Application to Senate Voting on the Minimum Wage

A widely noted empirical regularity of congressional behavior is that standing committees exert disproportionate influence on congressional choices. The observed phenomenon has a number of labels-committee influence, committee power, and (from the parent chamber's perspective) deference to committees-and a large body of theoretical and empirical research has sought to determine when and why it exists. This paper takes as given only the weakest form the observation, namely, that committee power exists sometimes. It does not directly address the questions of when and why committee power exists, although much of the relevant literature is reviewed. Rather, it focuses on a prerequisite to the resolution of disputes about committee power. How can committee power be assessed empirically? Section I reviews three classes of explanations and identifies obstacles to convincing empirical tests of the accounts. Section II introduces an econometric approach for analyzing committee power. Section III applies the technique to a sequence of votes on minimum wage legislation in the Senate in 1977. Section IV extends the technique to multi-dimensional choice spaces. Section V is a discussion and summary