An analytic Pade-motivated QCD coupling

We consider a modification of the Minimal Analytic (MA) coupling of Shirkov and Solovtsov. This modified MA (mMA) coupling reflects the desired analytic properties of the space-like observables. We show that an approximation by Dirac deltas of its discontinuity function $\rho$ is equivalent to a Pad\'e (rational) approximation of the mMA coupling that keeps its analytic structure. We propose a modification to mMA that, as preliminary results indicate, could be an improvement in the evaluation of low-energy observables compared with other analytic couplings.Comment: 2 pages, 1 figure (double), to appear in the Proceedings of the VIII Latin American Symposium on Nuclear Physics and Applications, Santiago, Chile, 15-19 December 2009. Poster presented by H. E. Martine

Galaxies infalling into groups: filaments vs. isotropic infall

We perform a comparative analysis of the properties of galaxies infalling into groups classifying them accordingly to whether they are: falling along filamentary structures; or they are falling isotropically. For this purpose, we identify filamentary structures connecting massive groups of galaxies in the SDSS. We perform a comparative analysis of some properties of galaxies in filaments, in the isotropic infall region, in the field, and in groups. We study the luminosity functions (LF) and the dependence of the specific star formation rate (SSFR) on stellar mass, galaxy type, and projected distance to the groups that define the filaments. We find that the LF of galaxies in filaments and in the isotropic infalling region are basically indistinguishable between them, with the possible exception of late-type galaxies. On the other hard, regardless of galaxy type, their LFs are clearly different from that of field or group galaxies. Both of them have characteristic absolute magnitudes and faint end slopes in between the field and group values. More significant differences between galaxies in filaments and in the isotropic infall region are observed when we analyse the SSFR. We find that galaxies in filaments have a systematically higher fraction of galaxies with low SSFR as a function of both, stellar mass and distance to the groups, indicating a stronger quenching of the star formation in the filaments compared to both, the isotropic infalling region, and the field. Our results suggest that some physical mechanisms that determine the differences observed between field galaxies and galaxies in systems, affect galaxies even when they are not yet within the systems.Comment: Accepted in MNRAS, 10 pages, 8 figure

Comparing galaxy populations in compact and loose groups of galaxies III. Effects of environment on star formation

Aims. This paper is part of a series in which we systematically compare the properties of galaxies in compact groups, loose groups, and the field. In this paper we focus our study on the age and star formation in galaxies. Methods. For galaxies in selected samples of compact groups, loose groups, and field galaxies, we compare the distributions of Dn (4000) as an age indicator and the specific star formation rate as an indicator of on-going star formation. We analyse the dependence of these parameters on galaxy type and stellar mass and, for group galaxies, their dependence on the dynamic state of the system. We study the relative fraction of galaxies dominated by old stellar populations as a function of galaxy stellar mass. We perform a similar analysis for galaxies that have high specific star formation rates. Results. Galaxies in compact groups have, on average, older stellar populations than their loose-group or field counterparts. Early-type galaxies in compact groups formed their stars and depleted their gas content more rapidly than in the other environments. We have found evidence of two populations of late-type galaxies in dynamically old compact groups: one with normal specific star formation rates and another with markedly reduced star formation. Conclusions. Processes that transform galaxies from star forming to quiescent act upon galaxies faster and more effectively in compact groups. The unique characteristics of compact groups make them an extreme environment for galaxies, where the transition to quiescence occurs rapidly.Fil: Coenda, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Muriel, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Martinez Atencio, Hector Julian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin

Investigating the Impacts of Monetary Policy on Income Inequality in Developed Nations: Case Study of the Euro Area, Japan and the United States

This paper tries to evaluate the effect that unconventional monetary policy has had on income inequality for the set of Eurozone countries, the United States and Japan using an unbalanced panel data model over the period from 1980 to 2021, first jointly and then individually, using different regressions for each case. Based on the regression model analyzed, the study attempts to analyze the relationship between money supply and income inequality as measured by the Gini index using fixed effects and random effects for our panel data model. The study reveals the importance of the money supply variable in reducing inequality when all countries are analyzed as a whole. For Eurozone countries, the common monetary policy created from 1999 onwards led to an increase in inequality, however the implementation of the unconventional monetary policy used from 2015 onwards had a beneficial effect on inequality reduction. The same result is found for the European Monetary Union countries. However, for the United States and Japan it is significantly concluded that the conventional monetary policies carried out since 1980 and, subsequently, the unconventional monetary policies have not only failed to reduce inequality, but have contributed to increase it for the aforementioned countries

The evolution of the bi-modal colour distribution of galaxies in SDSS groups

We analyse $u-r$ colour distributions for several samples of galaxies in groups drawn from the Fourth Data Release of the Sloan Digital Sky Survey. For all luminosity ranges and environments considered the colour distributions are well described by the sum of two Gaussian functions. We find that the fraction of galaxies in the red sequence is an increasing function of group virial mass. We also study the evolution of the galaxy colour distributions at low redshift, $z\le0.18$ in the field and in groups for galaxies brighter than $M_r-5\log(h)=-20$, finding significant evidence of recent evolution in the population of galaxies in groups. The fraction of red galaxies monotonically increases with decreasing redshift, this effect implies a much stronger evolution of galaxies in groups than in the field.Comment: 7 pages, 6 figures, submited to MNRAS after minor revisio

SNR-calibrated Type Ia supernova models

Current Type Ia supernova (SN Ia) models can reproduce most visible+IR + UV observations. In the X-ray band, the determination of elemental abundance ratios in supernova remnants (SNRs) through their spectra has reached enough precision to constrain SN Ia models. Martínez-Rodríguez et al have shown that the Ca/S mass ratio in SNRs cannot be reproduced with the standard nuclear reaction rates for a wide variety of SN Ia models, and suggested that the 12C+16O reaction rate could be overestimated by a factor as high as ten. We show that the same Ca/S ratio can be obtained by simultaneously varying the rates of the reactions 12C + 16O, 12C + 12C, 16O + 16O, and 16O(¿, a)12C within the reported uncertainties. We also show that the yields of the main products of SN Ia nucleosynthesis do not depend on the details of which rates are modified, but can be parametrized by an observational quantity such as Ca/S. Using this SNR-calibrated approach, we then proceed to compute a new set of SN Ia models and nucleosynthesis for both Chandrasekhar and sub-Chandrasekhar mass progenitors with a 1D hydrodynamics and nucleosynthesis code. We discuss the nucleosynthesis of the models as a function of progenitor metallicity, mass, and deflagration-to-detonation transition density. The yields of each model are almost independent on the reaction rates modified for a common Ca/S ratio.Peer ReviewedPostprint (author's final draft