In your face:A comparative field experiment on racial discrimination in Europe

We present the first large-scale comparative field experiment on appearance-based racial discrimination in hiring conducted in Europe. Using a harmonized methodology, we sent fictitious résumés to real vacancies in Germany, the Netherlands and Spain, randomly varying applicants’ ethnic ancestry (signaled foremost by name) and applicants’ racial appearance (signaled by photographs). Applicants are young-adult country nationals born to parents from over 40 different countries of ancestry (N = 12 783). We examine average differences in callback across four phenotypic groups and four regions of ancestry and present the first cross-country comparable estimates of appearance-based racial discrimination reported in the field-experimental literature. We find that applicants’ phenotype has a significant and independent effect on employers’ responses in Germany and the Netherlands, whereas in Spain we only find evidence of hiring discrimination for particular combinations of phenotype and ancestry, which suggests a less direct and more complex effect of phenotype in this country. Implications are discussed.</p

The spectral theorem of many-body Green's function theory when there are zero eigenvalues of the matrix governing the equations of motion

In using the spectral theorem of many-body Green's function theory in order to relate correlations to commutator Green's functions, it is necessary in the standard procedure to consider the anti-commutator Green's functions as well whenever the matrix governing the equations of motion for the commutator Green's functions has zero eigenvalues. We show that a singular-value decomposition of this matrix allows one to reformulate the problem in terms of a smaller set of Green's functions with an associated matrix having no zero eigenvalues, thus eliminating the need for the anti-commutator Green's functions. The procedure is quite general and easy to apply. It is illustrated for the field-induced reorientation of the magnetization of a ferromagnetic Heisenberg monolayer and it is expected to work for more complicated cases as well.Comment: 4 pages, 1 figure, accepted for publication in Physical Review B (16. May 2003

Chemical-bond Approach To The Electric Susceptibility Of Semiconductors

A simple model-independent method is developed to relate chemical bonds to the dielectric constant and other physical properties of tetrahedral semiconductors with the minimum number of parameters possible. For this purpose, we express 1(0), via the Kramers-Kronig relation, as a function of the zeroth and the first moments of 2(). The first moment is determined by the f sum rule while the zeroth moment can be calculated if the valence- and conduction-band wave functions are known. Since conduction bands are inadequately described by models that are analytically simple, we bypass the problem by using completeness to eliminate the conduction band entirely. The result is an expression for 1(0) which involves only valenceband wave functions. Since working in a localized representation is more convenient than in the Bloch representation, we introduce a generalized Wannier function of bonding character for the valence bands. Realizing that this is appropriate for only those semiconductors like diamond in which the bonding-antibonding coupling is weak, we build into our Wannier function the lacking antibonding character via a power-series expansion in the quantity V1V2 (Hall-Weaire parameters). Using Herman-Skillman values for the atomic orbitals, we obtain numerical results that agree with experiment to about 10%. © 1978 The American Physical Society.1741843185

Chemical Bond Approach To The Electric Susceptibility Of Semiconductors. Ii

The method previously developed to relate chemical bonds to the dielectric constant of elemental semiconductors is extended to the ionic tetrahedral III-V compounds. Expressions for the static dielectric constant and the average optical gap in terms of the generalized Wannier functions for the valence bands are obtained. Only two parameters are needed. The first is a measure of the antibonding character of the valence bands and the second is related to the ionic nature of these compounds. We have allowed the former to vary from compound to compound, while we have set the latter at a predetermined constant value, as prescribed by Coulson. We separate the energy gap into two analytical parts, "homopolar" and "heteropolar," thus directly confirming the ionicity scale established by Phillips. Finally, Coulson's definition of ionicity is reconciled with that of Phillips. © 1978 The American Physical Society.17124835484

The Orbit of the New Milky Way Globular Cluster FSR1716 =VVV-GC05

Indexación: Scopus.We use deep, multi-epoch near-IR images of the VISTA Variables in the Via Lictea (VVV) Survey to measure proper motions (PMs) of stars in the Milky Way globular cluster (GC) FSR1716 = VVV-GC05. The colormagnitude diagram of this object, made by using PM-selected members, shows an extended horizontal branch, nine confirmed RR Lyrae (RRL) members in the instability strip, and possibly several hotter stars extending to the blue. Based on the fundamental-mode (ab-type) RRL stars that move coherently with the cluster, we confirmed that FSR1716 is an Oosterhoff I GC with a mean period aPabn = 0.574 days. Intriguingly, we detect tidal extensions to both sides of this cluster in the spatial distribution of PM-selected member stars. Also, one of the confirmed RRabs is located -11 arcmin in projection from the cluster center, suggesting that FSR1716 may be losing stars due to the gravitational interaction with the Galaxy. We also measure radial velocities (RVs) for five cluster red giants selected using the PMs. The combination of RVs and PMs allow us to compute for the first time the orbit of this GC, using an updated Galactic potential. The orbit results to be confined within|Zmax| < 2.0 kpc, and has eccentricity 0.4 < e < 0.6, with perigalactic distance 1.5 < Rperi (kpc) < 2.3, and apogalactic distance 5.3 < Rapo (kpc) < 6.4. We conclude that, in agreement with its relatively low metallicity ([Fe/H] =-1.4 dex), this is an inner-halo GC plunging into the disk of the Galaxy. As such, this is a unique object with which to test the dynamical processes that contribute to the disruption of Galactic GCs. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aacd0

CMOS x-rays detector array based on scintillating light guides

This paper describes a pixel imaging array consisting in 400µm x 400µm photodiodes fabricated in CMOS technology. An array of scintillating CsI:Tl crystals is placed above the photodiodes. These crystals are encapsulated in aluminum walls, forming a light path that guides the visible light produced by the scintillating crystal into the photodiodes. In This way, the x-ray energy is first converted into visible light which is then detected by the photodiode at the end of each light guide. The scintillator is 800 µm thick, absorbing almost all 20keV x-ray photons. Usually, the spatial resolution of the scintillating x-ray detectors is identical to the scintillator thickness. By using the light guides, the scintillator thickness can be increased without decreasing the spatial resolution. The increase of the scintillator thickness is desirable in order to increase the x-rays absorption efficiency. Tests carried out on the system show very promising results near 20keV

The Single-Particle Spectral Function of 16O^{16}{\rm O}

The influence of short-range correlations on the $p$-wave single-particle spectral function in $^{16}{\rm O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum components, is found to be small in the $p$-shell quasihole wave functions. It is therefore unlikely that studies of quasihole momentum distributions using the $(e,e'p)$ reaction will reveal a significant contribution of high momentum components. Instead, high-momentum components become increasingly more dominant at higher excitation energy. The above observations are consistent with the energy distribution of high-momentum components in nuclear matter.Comment: 5 pages, RevTeX, 3 figure

Ultra Long Period Cepheids: a primary standard candle out to the Hubble flow

The cosmological distance ladder crucially depends on classical Cepheids (with P=3-80 days), which are primary distance indicators up to 33 Mpc. Within this volume, very few SNe Ia have been calibrated through classical Cepheids, with uncertainty related to the non-linearity and the metallicity dependence of their period-luminosity (PL) relation. Although a general consensus on these effects is still not achieved, classical Cepheids remain the most used primary distance indicators. A possible extension of these standard candles to further distances would be important. In this context, a very promising new tool is represented by the ultra-long period (ULP) Cepheids (P \geq 80 days), recently identified in star-forming galaxies. Only a small number of ULP Cepheids have been discovered so far. Here we present and analyse the properties of an updated sample of 37 ULP Cepheids observed in galaxies within a very large metallicity range of 12+log(O/H) from ~7.2 to 9.2 dex. We find that their location in the colour(V-I)-magnitude diagram as well as their Wesenheit (V-I) index-period (WP) relation suggests that they are the counterparts at high luminosity of the shorter-period (P \leq 80 days) classical Cepheids. However, a complete pulsation and evolutionary theoretical scenario is needed to properly interpret the true nature of these objects. We do not confirm the flattening in the studied WP relation suggested by Bird et al. (2009). Using the whole sample, we find that ULP Cepheids lie around a relation similar to that of the LMC, although with a large spread (~0.4 mag).Comment: 8 pages, 4 figures, accepted for publication in Astrophysics & Space Scienc