Multigroup Segregation Patterns and Determinants: The Case of Immigrants in an Italian City

Models of race-based segregation establish that individual characteristics or housing market attributes are complementary causes of the observed level of races’ concentration inside an urban space. The goal of this work is to establish which variables, and in which order of magnitude, among individual characteristics, housing features, and local amenities correlate with immigrants’ segregation, in the case of consistent within-city immigrants’ mobility. We capture the degree of segregation for different immigration groups by a local concentration statistics that is directly obtained from segregation curves, and we use data on the Verona Municipality as a case study. We find strong evidence in favor of the role of the housing market and housing ownership distribution across city areas

Multiple light scattering in atomic media : from metasurfaces to the ultimate refractive index

(English) Our ability to confine, guide, and bend light has led to astonishing technological achievements, playing a fundamental role in diverse fields like microscopy, photochemistry, telecommunications or material design. The key property of materials that allows to control light is the refractive index. Notably, regardless of very different microscopic structures, all natural materials exhibit a modest, near-unity index of refraction, n ~ 1. This universality suggests the existence of some simple, ubiquitous origin, whose complete characterization from microscopic considerations, surprisingly, is still missing. Moreover, one can wonder which principles might allow to synthesize a material with an ultra-high index, to boost the performance of photonic devices. In this thesis, we address these questions from an atomic-physics standpoint, exploring if the macroscopic optical properties can be related to simple, electrodynamical processes occurring between well-separated atoms, which only interact via light scattering. Standard theories neglect that light can be scattered multiple times, and lead to unphysical predictions when strong interference occurs between the coherent atomic emission, such as in dense atomic ensembles or ordered lattices. We here develop new techniques to address the physics of multiple light scattering, with the ultimate goal of understanding the fundamental limits to the refractive index, as well as proposing unexpected photonic applications. Our results are divided in three parts. First, we investigate an ensemble of ideal atoms with increasing atomic density, starting from the dilute gas limit, up to dense regimes where a non-perturbative treatment of multiple scattering and near-field interactions is required. In this situation, we find that these effects limit the index to a maximum value of n ~ 1.7, in contrast with standard theories. We propose an explanation based upon strong-disorder renormalization group theory, in which the near-field interactions combined with random atomic positions result in an inhomogeneous broadening of the atomic resonance frequencies. This basic mechanism ensures that regardless of the physical atomic density, light at any given frequency only interacts with at most a few near-resonant atoms per cubic wavelength, thus limiting the index attainable. Afterwards, we show that a radically different behavior is expected for an ideal, atomic crystal. As long as the inter-atomic interactions are only mediated by multiple scattering, each 2D array of the crystal exhibits a lossless, single-mode response, which builds up a very large and purely real refractive index. To address the limits to this picture, we extend our theoretical analysis to much higher densities, where the electronic orbitals on neighboring nuclei begin to overlap. We develop a minimal model to include the onset of this regime into our non-perturbative analysis of multiple light scattering, arguing that the emergence of quantum magnetism, density-density correlations and tunneling dynamics of the electrons effectively suppresses the single-mode response, decreasing the index back to unity. Nonetheless, right before the onset of chemistry, our theory predicts that an ultra-high-index (n ~ 30) and low-loss material could in principle be allowed by the laws of nature. Finally, inspired by the impressive optical response of atomic arrays, we propose their use as a more complex optical device, namely a thin lens. The building blocks of this "atomic metalens" are composed of three consecutive 2D arrays, whose distance and lattice constants are suitably chosen to guarantee a high transmission of light, as well as an arbitrary phase shift. To characterize its efficiency and prove its robustness against losses, we perform large-scale numerical simulations, on a number of atoms between one and two orders of magnitude larger than comparable works.(Español) Nuestra capacidad de confinar y guiar la luz nos ha llevado a logros tecnológicos asombrosos, jugando un papel fundamental en campos tan diversos como la fotoquímica, las telecomunicaciones o el diseño de materiales. La propiedad clave de un material para controlar la luz es su índice de refracción. En particular, todos los materiales naturales exhiben un índice de refracción modesto, cercano a la unidad, n ~ 1. Esta universalidad sugiere la existencia de algún origen simple y ubicuo, cuya caracterización completa a partir de consideraciones microscópicas, sorprendentemente, aún falta. Además, para aumentar el rendimiento de los dispositivos fotónicos, es crucial entender si los principios físicos permiten o prohíben la síntesis de materiales con índices más altos. En esta tesis, abordamos estas cuestiones desde un punto de vista atómico, estudiando si las propiedades ópticas macroscópicas pueden deberse a procesos electrodinámicos entre átomos bien separados, que solo interactúan a través de la dispersión de la luz. Las teorías estándar ignoran que la luz puede dispersarse varias veces y conducen a predicciones erradas en situaciones de fuerte interferencia, como en redes cristalinas o conjuntos densos de átomos. Aquí, desarrollamos nuevas técnicas para tratar la dispersión múltiple de la luz, con el objetivo final de comprender los límites fundamentales del índice de refracción, así como proponer aplicaciones fotónicas innovadoras. Nuestros resultados se dividen en tres partes. Primero, investigamos un conjunto desordenado de átomos con densidad creciente, hasta regímenes donde se requiere un tratamiento completo de la dispersión múltiple y de las interacciones de campo cercano. En esta situación, encontramos que estos efectos limitan el índice de refracción a un valor máximo de n ~ 1,7. Proponemos una explicación basada en la teoría del grupo de renormalización, en la que las interacciones de campo cercano, combinadas con posiciones atómicas aleatorias, desarrollan una ampliación no homogénea de las frecuencias atómicas de resonancia. Este mecanismo asegura que, independientemente de la densidad atómica, la luz (para cualquier frecuencia dada) solo interactúa con unos pocos átomos resonantes por unidad cúbica de longitud de onda, limitando la respuesta óptica. Un comportamiento radicalmente diferente se manifiesta en una red cristalina de átomos. Siempre que las interacciones solo estén mediadas por dispersión múltiple, cada capa del cristal exhibe una respuesta monomodo sin pérdidas, que genera un índice de refracción muy grande y puramente real. Para abordar los límites de esta respuesta física, ampliamos nuestro análisis teórico hasta densidades tan altas que los orbitales electrónicos de los núcleos vecinos comienzan a superponerse. Desarrollamos un modelo para incluir el inicio de este régimen en nuestro análisis, argumentando que la aparición del magnetismo cuántico, las correlaciones de densidad y la dinámica de efecto túnel de los electrones suprimen efectivamente la respuesta monomodo, bajando nuevamente el índice a la unidad. No obstante, justo antes del inicio de los procesos químicos, nuestra teoría predice la posibilidad teórica de sintetizar un material con un índice de refracción sorprendentemente alto (n ~ 30) y pérdidas bajas. Por último, inspirándonos en la impresionante respuesta óptica de las redes atómicas, proponemos su uso para imitar un dispositivo óptico complejo, a saber, una lente delgada. El componente básico de esta "metalente atómica" está compuesto por tres redes atómicas bidimensionales consecutivas, cuyas distancias y constantes de red se eligen adecuadamente para garantizar una alta transmisión de la luz, así como un cambio de fase arbitrario. Para caracterizar su eficiencia y probar su robustez frente a pérdidas, realizamos simulaciones numéricas incluyendo un gran número de átomos, entre uno y dos órdenes de magnitud mayor que en trabajos comparables.DOCTORAT EN FOTÒNICA (Pla 2013

Robust Inference for Inverse Stochastic Dominance

The notion of inverse stochastic dominance is gaining increasing support in risk, inequality, and welfare analysis as a relevant criterion for ranking distributions, which is alternative to the standard stochastic dominance approach. Its implementation rests on comparisons of two distributions\u2019 quantile functions, or of their multiple partial integrals, at fixed population proportions. This article develops a novel statistical inference model for inverse stochastic dominance that is based on the influence function approach. The proposed method allows model-free evaluations that are limitedly affected by contamination in the data. Asymptotic normality of the estimators allows to derive tests for the restrictions implied by various forms of inverse stochastic dominance. Monte Carlo experiments and an application promote the qualities of the influence function estimator when compared with alternative dominance criteria

Scaling and multiscaling in financial series: a simple model

We propose a simple stochastic volatility model which is analytically tractable, very easy to simulate and which captures some relevant stylized facts of financial assets, including scaling properties. In particular, the model displays a crossover in the log-return distribution from power-law tails (small time) to a Gaussian behavior (large time), slow decay in the volatility autocorrelation and multiscaling of moments. Despite its few parameters, the model is able to fit several key features of the time series of financial indexes, such as the Dow Jones Industrial Average, with a remarkable accuracy.Comment: 32 pages, 5 figures. Substantial revision, following the referee's suggestions. Version to appear in Adv. in Appl. Proba

Inference for the neighborhood inequality index

The neighborhood inequality (NI) index measures aspects of spatial inequality in the distribution of incomes within a city. The NI index is a population average of the normalized income gap between each individual's income (observed at a given location in the city) and the incomes of the neighbors located within a certain distance range. The approach overcomes the Modiable Areal Units Problem affecting local inequality measures. This paper provides minimum bounds for the NI index standard error and shows that unbiased estimators can be identied under fairly common hypothesis in spatial statistics. Results from a Monte Carlo study support the relevance of the approximations. Rich income data are then used to infer about trends of neighborhood inequality in Chicago, IL over the last 35 years

Robust cross-country analysis of inequality of opportunity

International rankings of countries based on inequality of opportunity indices may not be robust vis-vis the specific metric adopted to measure opportunities. Indices often aggregate relevant information and neglect to control for normatively irrelevant distributional factors. This paper shows that gap curves can be estimated from cross-sectional data and adopted to test hypotheses about robust cross-country comparisons of (in)equality of opportunity. (C) 2019 The Authors. Published by Elsevier B.V

Application of the EU-SILC 2011 data module "intergenerational transmission of disadvantage" to robust analysis of inequality of opportunity

This data article describes the original data, the sample selection process and the variables used in Andreoli and Fusco (Andreoli and Fusco, 2019) to estimate gap curves for a sample of European countries. Raw data are from 2011 roaster of EU-SILC, cross-sectional sample of module "intergenerational transmission of disadvantage". This article reports descriptive statistics of the using sample. It also discusses the algorithm adopted to estimate the main effects and details the content of additional Stata files stored on the online repository. These additional files contain raw estimates from bootstrapped samples, which form the basis for estimating gap curves and their variance-covariance matrices. The data article also reports representations of gap curves for all 16 selected countries. (C) 2019 The Authors. Published by Elsevier Inc

Experimental bilocality violation without shared reference frames

Non-classical correlations arising in complex quantum networks are attracting growing interest, both from a fundamental perspective and for potential applications in information processing. In particular, in an entanglement swapping scenario a new kind of correlations arise, the so-called nonbilocal correlations that are incompatible with local realism augmented with the assumption that the sources of states used in the experiment are independent. In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to presence of shared reference frames between the parties. Here, we experimentally address this point showing that false positive nonbilocal quantum correlations can be observed even though the sources of states are independent. To overcome this problem, we propose and demonstrate a new scheme for the violation of bilocality that does not require shared reference frames and thus constitute an important building block for future investigations of quantum correlations in complex networks.Comment: 10 page