Accurate nucleon electromagnetic form factors from dispersively improved chiral effective field theory

We present a theoretical parametrization of the nucleon electromagnetic form factors (FFs) based on a combination of chiral effective field theory and dispersion analysis. The isovector spectral functions on the two-pion cut are computed using elastic unitarity, chiral pion-nucleon amplitudes, and timelike pion FF data. Higher-mass isovector and isoscalar t-channel states are described by effective poles, whose strength is fixed by sum rules (charges, radii). Excellent agreement with the spacelike proton and neutron FF data is achieved up to Q^2 \sim 1 GeV^2. Our parametrization provides proper analyticity and theoretical uncertainty estimates and can be used for low-Q^2 FF studies and proton radius extraction.Comment: 5 pages, 3 figures, 2 table

Harmonic mappings and conformal minimal immersions of Riemann surfaces into RN

We prove that for any open Riemann surface N, natural number N ≥ 3, non-constant harmonic map h:N→R N−2 and holomorphic 2-form H on N , there exists a weakly complete harmonic map X=(Xj)j=1,…,\scN:N→R\scN with Hopf differential H and (Xj)j=3,…,\scN=h. In particular, there exists a complete conformal minimal immersion Y=(Yj)j=1,…,\scN:N→R\scN such that (Yj)j=3,…,\scN=h . As some consequences of these results (1) there exist complete full non-decomposable minimal surfaces with arbitrary conformal structure and whose generalized Gauss map is non-degenerate and fails to intersect N hyperplanes of CP\scN−1 in general position. (2) There exist complete non-proper embedded minimal surfaces in R\scN, ∀\scN>3.Ministerio de Ciencia y Tecnología MTM2007-61775Ministerio de Ciencia y Tecnología MTM2007-64504Junta de Andalucía P09-FQM-508

Complete minimal surfaces and harmonic functions

We prove that for any open Riemann surface N and any non constant harmonic function h : N → R, there exists a complete conformal minimal immersion X : N → R3 whose third coordinate function coincides with h. As a consequence, completeminimal surfaceswith arbitrary conformal structure andwhose Gauss map misses two points are constructed.Ministerio de Educación y Ciencia MTM2007-61775Ministerio de Educación y Ciencia MTM2007-64504Junta de Andalucía P06-FQM-01642

Phylogeographic Structure of the Fossorial Long-Clawed Mouse Chelemys macronyx (Cricetidae: Sigmodontinae)

We present a phylogeographic study of the fossorial sigmodontine mouse Chelemys macronyx. Analyses were based on mitochondrial DNA sequences of specimens collected over most of distributional range of the species. Results showed that C. macronyx has a shallow genealogy that is geographically structured into 2 main clades: one in the northern part of the species distribution, at high-Andean localities in the Argentinean provinces of Mendoza and northern Neuquén, and the other covering the majority of its distributional range at medium- to low-elevation localities from northwestern Neuquén to the south. The northern clade appears to have been demographically stable, while the southern clade presents signals of demographic expansion. These results suggest that current genetic variation of C. macronyx may have originated from 2 refugia.Fil: Alarcón, Oriet. Universidad de Concepción; ChileFil: D'elía, Guillermo. Universidad Austral de Chile; Chile. Centro de Investigación en Ecosistemas de la Patagonia; ChileFil: Lessa, Enrique P.. Universidad de la República. Facultad de Ciencias; UruguayFil: Pardiñas, Ulises Francisco J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin