The Cepheid Phase Lag Revisited

We compute the phase lags between the radial velocity curves and the light curves $\Delta \Phi_1= \phi^{V_r}_1 - \phi^{mag}_1$ for classical Cepheid model sequences both in the linear and the nonlinear regimes. The nonlinear phase lags generally fall below the linear ones except for high period models where they lie above, and of course for low pulsation amplitudes where the two merge. The calculated phase lags show good agreement with the available observational data of normal amplitude Galactic Cepheids. The metallicity has but a moderate effect on the phase lag, while the mass-luminosity relation and the parameters of the turbulent convective model (time-dependent mixing length) mainly influence the modal selection and the period, which is then reflected in the period -- $\Delta \Phi_1$ diagram. We discuss the potential application of this observable as a discriminant for pulsation modes and as a test for ultra-low amplitudes (ULA) pulsation.Comment: 11 pages, 8 figures, accepted for publication in ApJ, minor revisions in the text and figures, (black and white version available from 2nd author's website

The Holographic Disorder-Driven Superconductor-Metal Transition

We implement the effects of disorder on a holographic superconductor by introducing a random chemical potential on the boundary. We demonstrate explicitly that increasing disorder leads to the formation of islands where the superconducting order is enhanced and subsequently to the transition to a metal. We study the behavior of the superfluid density and of the conductivity as a function of the strength of disorder. We find explanations for various marked features in the conductivities in terms of hydrodynamic quasi-normal modes of the holographic superconductors. These identifications plus a particular disorder-dependent spectral weight shift in the conductivity point to a signature of the Higgs mode in the context of disordered holographic superconductors. We observe that the behavior of the order parameter close to the transition is not mean-field type as in the clean case, rather we find robust agreement with $\exp(- A\, |T-T_c|^{-\nu})$, with $\nu =1.03\pm 0.02$ for this disorder-driven smeared transition.Comment: 7 pages, 8 figures. v2: minor improvements of the Higgs mode and smeared phase transition discussions. Typos corrected. Published versio

Analysis of the Q^2-dependence of charged-current quasielastic processes in neutrino-nucleus interactions

We discuss the observed disagreement between the Q^2 distributions of neutrino-nucleus quasielastic events, measured by a number of recent experiments, and the predictions of Monte Carlo simulations based on the relativistic Fermi gas model. The results of our analysis suggest that these discrepancies are likely to be ascribable to both the breakdown of the impulse approximation and the limitations of the Fermi gas description. Several issues related to the extraction of the Q^2 distributions from the experimental data are also discussed, and new kinematical variables, which would allow for an improved analysis, are proposed.Comment: 8 pages, 8 figures, 1 tabl

Parity Doubling and SU(2)_L x SU(2)_R Restoration in the Hadron Spectrum

We construct the most general nonlinear representation of chiral SU(2)_L x SU(2)_R broken down spontaneously to the isospin SU(2), on a pair of hadrons of same spin and isospin and opposite parity. We show that any such representation is equivalent, through a hadron field transformation, to two irreducible representations on two hadrons of opposite parity with different masses and axial couplings. This implies that chiral symmetry realized in the Nambu-Goldstone mode does not predict the existence of degenerate multiplets of hadrons of opposite parity nor any relations between their couplings or masses.Comment: 4 pages, 1 figure; v3: Note added to clarify implications for hadrons that do not couple to pions: Chiral symmetry can be realized linearly on such states, leading to parity doubling. To the extent that they are parity doubled, these hadrons must decouple from pions, a striking prediction that can be tested experimentally. This applies to the work of L. Glozman and collaborator

Holographic p-wave Superconductor with Disorder

We implement the effects of disorder on a holographic p-wave superconductor by introducing a random chemical potential which defines the local energy of the charge carriers. Since there are various possibilities for the orientation of the vector order parameter, we explore the behaviour of the condensate in the parallel and perpendicular directions to the introduced disorder. We clarify the nature of various branches representing competing solutions and construct the disordered phase diagram. We find that moderate disorder enhances superconductivity as determined by the value of the condensate. Though we mostly focus on uncorrelated noise, we also consider a disorder characterized by its spectral properties and study in detail its influence on the spectral properties of the condensate and charge density. We find fairly universal responses of the resulting power spectra characterized by linear functions of the disorder power spectrum.Fil: Arean, Daniel. Instituto Max Planck de Física; AlemaniaFil: Pando Zayas, Leopoldo. University of Michigan; Estados UnidosFil: Salazar, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Scardicchio, Antonello. The Abdus Salam. International Centre for Theoretical Physics; Italia. Columbia University; Estados Unidos. Princeton University; Estados Unido

A Dirty Holographic Superconductor

We study the effects of disorder on a holographic superconductor by introducing a random chemical potential on the boundary. We consider various realizations of disorder and find that the critical temperature for superconductivity is enhanced. We also present evidence for a precise form of renormalization in this system. Namely, when the random chemical potential is characterized by a Fourier spectrum of the form $k^{-2\alpha}$ we find that the spectra of the condensate and the charge density are again power-laws, whose exponents are accurately and universally governed by linear functions of $\alpha$.Comment: 5 pages, 8 figures. v3: discussion improved, references added, typos corrected, results unchange

Hydrodynamical Survey of First Overtone Cepheids

A hydrodynamical survey of the pulsational properties of first overtone Galactic Cepheids is presented. The goal of this study is to reproduce their observed light- and radial velocity curves. The comparison between the models and the observations is made in a quantitative manner on the level of the Fourier coefficients. Purely radiative models fail to reproduce the observed features, but convective models give good agreement. It is found that the sharp features in the Fourier coefficients are indeed caused by the P1/P4 = 2 resonance, despite the very large damping of the 4th overtone. For the adopted mass-luminosity relation the resonance center lies near a period of 4.2d +/- 0.2 as indicated by the observed radial velocity data, rather than near 3.2d as the light-curves suggest.Comment: ApJ, 12 pages, (slightly) revise

Breaking the core-envelope symmetry in p-mode pulsating stars

It has been shown that there is a potential ambiguity in the asteroseismic determination of the location of internal structures in a pulsating star. We show how, in the case of high-order non-radial acoustic modes, it is possible to remove this ambiguity by considering modes of different degree. To support our conclusions we have investigated the seismic signatures of sharp density variations in the structure of quasi-homogeneous models.Comment: 3 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Non-HFE Hepatic Iron Overload.

Numerous clinical entities have now been identified to cause pathologic iron accumulation in the liver. Some are well described and have a verified hereditary basis; in others the genetic basis is still speculative, while in several cases nongenetic iron-loading factors are apparent. The non-HFE hemochromatosis syndromes identifies a subgroup of hereditary iron loading disorders that share with classic HFE-hemochromatosis, the autosomal recessive trait, the pathogenic basis (i.e., lack of hepcidin synthesis or activity), and key clinical features. Yet, they are caused by pathogenic mutations in other genes, such as transferrin receptor 2 (TFR2), hepcidin (HAMP), hemojuvelin (HJV), and ferroportin (FPN), and, unlike HFE-hemochromatosis, are not restricted to Caucasians. Ferroportin disease, the most common non-HFE hereditary iron-loading disorder, is caused by a loss of iron export function of FPN resulting in early and preferential iron accumulation in Kupffer cells and macrophages with high ferritin levels and low-to-normal transferrin saturation. This autosomal dominant disorder has milder expressivity than hemochromatosis. Other much rarer genetic disorders are associated with hepatic iron load, but the clinical picture is usually dominated by symptoms and signs due to failure of other organs (e. g., anemia in atransferrinemia or neurologic defects in aceruloplasminemia). Finally, in the context of various necro-inflammatory or disease processes (i.e., chronic viral or metabolic liver diseases), regional or local iron accumulation may occur that aggravates the clinical course of the underlying disease or limits efficacy of therapy