A really elementary proof of real Lüroth theorem

Sin resume

Chiral dynamics of hadrons in nuclei

In this talk I report on selected topics of hadron modification in the nuclear medium using the chiral unitary approach to describe the dynamics of the problems. I shall mention how antikaons, $\eta$, and $\phi$ are modified in the medium and will report upon different experiments done or planned to measure the $\phi$ width in the medium.Comment: 10 pgs, 3 figs. Invited talk in the Workshop on in Medium Hadron Physics, Giessen, Nov 200

The nature of the Lambda(1405)

We present here some results supporting the nature of the $\Lambda(1405)$ resonance as dynamically generated from the meson baryon interaction in coupled channels and resulting from the superposition of two close-by poles. We find support for this picture in the $K^- p \to \pi^0 \pi^0 \Sigma^0$ reaction, which shows a different shape than the one obtained from the $\pi ^- p \to K^0 \pi \Sigma$ reaction. We also call the attention to the $K^- p \to \gamma \pi \Sigma$ with $\pi \Sigma$ in the $\Lambda(1405)$ region, which shows a narrow peak in the calculations around 1420 MeV. We also report on recent calculations of the radiative decay of the two $\Lambda(1405)$ states and on reactions to obtain information on these decay modes. Finally, we present results for the $pp\to p K^+\Lambda(1405)$ reaction recently measured at ANKE/COSY and compare them with theoretical results.Comment: Talk given at the NSTAR2007 Workshop, Bonn September 200

Reparametrizing Swung Surfaces over the Reals

Let K⊆R be a computable subfield of the real numbers (for instance, Q). We present an algorithm to decide whether a given parametrization of a rational swung surface, with coefficients in K(i), can be reparametrized over a real (i.e., embedded in R) finite field extension of K. Swung surfaces include, in particular, surfaces of revolution

Λ(1405)\Lambda(1405) and Λˉ(1405)\bar\Lambda(1405) in J/ψJ/\psi four-body decays

We study the structure of the baryon resonances $\Lambda(1405)$ and $\bar\Lambda(1405)$ in $J/\psi$ four body decays $J/\psi\to \Sigma\bar \Sigma \pi\pi$ in the framework of a coupled channel chiral unitary approach. With still sufficient freedom for model parameters, the $\Lambda(1405)$ and $\bar\Lambda(1405)$ resonances are generated by simultaneously taking the meson baryon and meson anti-baryon final state interactions into account. The $\pi\Sigma$ ($\pi\bar\Sigma$) invariant mass distributions peak around 1410 MeV, which favors the assertion that the $\Lambda(1405)$ ($\bar\Lambda(1405)$) is a superposition of the two $\Lambda(1405)$ ($\bar\Lambda(1405)$) states which dominantly couple to $\bar K N$ ($K\bar N$) and $\pi\Sigma$ ($\pi\bar\Sigma$), respectively. We also calculate the amplitude for isospin I=1 which gives hints on a possible I=1 baryon resonance in the energy region of the $\Lambda(1405)$, which up to now has not been observed.Comment: 17 pages, 5 figures, version accepted for publication in Phys. Rev.

Ultraquadrics associated to affine and projective automorphisms

The concept of ultraquadric has been introduced by the authors as a tool to algorithmically solve the problem of simplifying the coefficients of a given rational parametrization in K(a) (t1, ..., tn) of an algebraic variety of arbitrary dimension over a field extension K(a). In this context, previous work in the one-dimensional case has shown the importance of mastering the geometry of 1-dimensional ultraquadrics (hypercircles). In this paper we study, for the first time, the properties of some higher dimensional ultraquadrics, namely, those associated to automorphisms in the field K(a) (t1, ..., tn), defined by linear rational (with common denominator) or by polynomial (with inverse also polynomial) coordinates. We conclude, among many other observations, that ultraquadrics related to polynomial automorphisms can be characterized as varieties K-isomorphic to linear varieties, while ultraquadrics arising from projective automorphisms are isomorphic to the Segre embedding of a blowup of the projective space along an ideal and, in some general case, linearly isomorphic to a toric variety. We conclude with some further details about the real-complex, 2-dimensional case, showing, for instance, that this family of ultraquadrics can be presented as a collection of ruled surfaces described by pairs of hypercircles. © 2014, Springer-Verlag Berlin Heidelberg

Chiral SU(3) Bethe Salpeter Model: Extension to SU(6) and SU(8) Spin-Flavor Symmetries

Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which incorporate vector meson degrees of freedom. In the charmless sector, the on-shell approximation to the Bethe-Salpeter (BS) approach successfully reproduces previous SU(3) WT results for the lowest-lying s--wave negative parity baryon resonances. It also provides some information on the dynamics of heavier ones and of the lightest d-wave negative parity resonances, as e.g. the Lambda(1520). For charmed baryons the scheme is consistent with heavy quark symmetry, and our preliminary results in the strangeness-less charm C=+1 sector describe the main features of the three-star J^P=1/2^- Lambda_c(2595) and J^P=3/2^- Lambda_c(2625) resonances. We also find a second broad J^P=1/2^- state close to the Lambda_c(2595)Comment: Presented at Chiral07: Chiral Symmetry in Hadron and Nuclear Physics November 13-16, 2007, Osaka University, Japa

Doing Biopolitics Differently? Radical Potential in the Post-2015 MDG and SDG Debates

Post print On institutional repository or subject-based repository after a 18 months embargo, withdraw

The Gaia-ESO Survey: Tracing interstellar extinction

Large spectroscopic surveys have enabled in the recent years the computation of three-dimensional interstellar extinction maps thanks to accurate stellar atmospheric parameters and line-of-sight distances. Such maps are complementary to 3D maps extracted from photometry, allowing a more thorough study of the dust properties. Our goal is to use the high-resolution spectroscopic survey Gaia-ESO in order to obtain with a good distance resolution the interstellar extinction and its dependency as a function of the environment and the Galactocentric position. We use the stellar atmospheric parameters of more than 5000 stars, obtained from the Gaia-ESO survey second internal data release, and combine them with optical (SDSS) and near-infrared (VISTA) photometry as well as different sets of theoretical stellar isochrones, in order to calculate line-of-sight extinction and distances. The extinction coefficients are then compared with the literature to discuss their dependancy on the stellar parameters and position in the Galaxy. Within the errors of our method, our work does not show that there is any dependence of the interstellar extinction coefficient on the atmospheric parameters of the stars. We do not find any evidence of the variation of E(J-H)/E(J-K) with the angle from the Galactic centre nor with Galactocentric distance. This suggests that we are dealing with a uniform extinction law in the SDSS ugriz bands and the near-IR JHKs bands. Therefore, extinction maps using mean colour-excesses and assuming a constant extinction coefficient can be used without introducing any systematic errors.Comment: 13 pages, 14 figures, 1 Appendix accepted for publication in Astronomy&Astrophysic