Chiral SU(3) Symmetry and Strangeness

In this talk we review recent progress on the systematic evaluation of the kaon and antikaon spectral functions in dense nuclear matter based on a chiral SU(3) description of the low-energy pion-, kaon- and antikaon-nucleon scattering data.Comment: 9 pages, 4 figures, invited talk given by M.F.M.L. at the SQM2001 conferenc

Kaon and antikaon properties in cold nuclear medium

We present results of a self-consistent calculation for the kaon and antikaon spectral functions in cold nuclear matter, using as input the kaon-nucleon and antikaon-nucleon scattering amplitudes of the vacuum. We investigate the effect of in-medium pion dressing on the antikaon-nucleon scattering amplitudes and antikaon spectral function. We find the influence of pion dressing to be minor on the antikaon spectral function and limited on the hyperon resonances causing only a small additional broadening. An exception is the \Sigma(1690). At nuclear saturation density an attractive mass shift of about 20 MeV and width of about 130 MeV is obtained. The kaon shows a repulsive mass increase of 36 MeV and a small width of the quasiparticle peak at saturation density.Comment: 8 pages, 4 figures, submitted to Heavy Ion Physic

Self-consistent antikaon dynamics in isospin-asymmetric nuclear medium

We investigate properties of antikaons and hyperon resonances in isospin-asymmetric nuclear medium, using a self-consistent, covariant scheme based on vacuum antikaon-nucleon scattering amplitude.Comment: 9 pages, 5 figures, uses budapest.sty (included);to be published in the Proceedings of the Budapest'2002 Workshop on Quark and Hadron Dynamics, Budapest, Hungary, 3-7 March 200

Chiral symmetry, strangeness and resonances

We review the important role played by the chiral SU(3) symmetry in predicting the properties of antikaons and hyperon resonances in cold nuclear matter. Objects of crucial importance are the meson-baryon scattering amplitudes obtained within the chiral coupled-channel effective field theory. The formation of baryon resonances as implied by chiral coupled-channel dynamics is discussed. Results for antikaon and hyperon-resonance spectral functions are presented for isospin symmetric and asymmetric matter.Comment: invited talk presented by M.F.M.L. at the 18th Nishinomiya Yukawa Memorial Symposium, 21 pages, 12 figure

Dynamical light vector mesons in low-energy scattering of Goldstone bosons

We present a study of Goldstone boson scattering based on the flavor SU(3) chiral Lagrangian formulated with vector mesons in the tensor field representation. A coupled-channel channel computation is confronted with the empirical s- and p-wave phase shifts, where good agreement with the data set is obtained up to about 1.2 GeV. There are two relevant free parameters only, the chiral limit value of the pion decay constant and the coupling constant characterizing the decay of the rho meson into a pair of pions. We apply a recently suggested approach that implements constraints from micro- causality and coupled-channel unitarity. Generalized potentials are obtained from the chiral Lagrangian and are expanded in terms of suitably constructed conformal variables. The partial-wave scattering amplitudes are defined as solutions of non-linear integral equations that are solved by means of an N/D ansatz.Comment: 15 pages, 8 figures, typos corrected, accepted for publication in Physics Letters

ASPfun: a typed functional active object calculus

This paper provides a sound foundation for autonomous objects communicating by remote method invocations and futures. As a distributed extension of ς-calculus we define ASPfun, a calculus of functional objects, behaving autonomously and communicating by a request-reply mechanism: requests are method calls handled asynchronously and futures represent awaited results for requests. This results in an object language enabling a concise representation of a set of active objects interacting by asynchronous method invocations. This paper first presents the ASPfun calculus and its semantics. Then, we provide a type system for ASPfun which guarantees the “progress” property. Most importantly, ASPfun has been formalised; its properties have been formalised and proved using the Isabelle theorem prover and we consider this as an important step in the formalization of distributed languages. This work was also an opportunity to study different binder representations and experiment with two of them in the Isabelle/HOL theorem prover

A locally nameless theory of objects

This paper presents the formalisation of an object calculus in Isabelle/HOL highlighting the binder technique called locally nameless1. This techniques has its origins already in a note at the end of de Bruijn’s paper [5] introducing the classical de Bruijn indices. In the last few years, with the advent of mechanized proofs in the domain of programming languages, e.g. [1], this technique attracted new attention. The most recent work on locally nameless technique [2] provides cofinite quantification, necessary for proving non-trivial properties. Indeed the de Bruijn indices are often criticised, as being too technical, that is why alternative techniques are investigated. The de Bruijn indices method, however, is known to be reliable, and is often chosen in order to focus on aspects of programming languages unrelated to variable bindings. With locally nameless techniques, one expects to spend less time proving auxiliary lemmas dealing with variable bind- ings, but also to obtain theorems that are more convincing because closer to the paper version. Our contributions are a formalisation in Isabelle/HOL of ς-calculus; and an in depth comparison of both locally nameless and de Bruijn complete mechanisations including specification and proofs

Correlated defects, metal-insulator transition, and magnetic order in ferromagnetic semiconductors

The effect of disorder on transport and magnetization in ferromagnetic III-V semiconductors, in particular (Ga,Mn)As, is studied theoretically. We show that Coulomb-induced correlations of the defect positions are crucial for the transport and magnetic properties of these highly compensated materials. We employ Monte Carlo simulations to obtain the correlated defect distributions. Exact diagonalization gives reasonable results for the spectrum of valence-band holes and the metal-insulator transition only for correlated disorder. Finally, we show that the mean-field magnetization also depends crucially on defect correlations.Comment: 4 pages RevTeX4, 5 figures include

Optical Versus Mid-Infrared Spectroscopic Classification of Ultraluminous Infrared Galaxies

The origin of huge infrared luminosities of ultraluminous infrared galaxies (ULIGs) is still in question. Recently, Genzel et al. made mid-infrared (MIR) spectroscopy of a large number of ULIGs and found that the major energy source in them is massive stars formed in the recent starburst activity; i.e., $\sim$ 70% -- 80% of the sample are predominantly powered by the starburst. However, it is known that previous optical spectroscopic observations showed that the majority of ULIGs are classified as Seyferts or LINERs (low-ionization nuclear emission-line regions). In order to reconcile this difference, we compare types of emission-line activity for a sample of ULIGs which have been observed in both optical and MIR. We confirm the results of previous studies that the majority of ULIGs classified as LINERs based on the optical emission-line diagnostics turn to be starburst-dominated galaxies based on the MIR ones. Since the MIR spectroscopy can probe more heavily-reddened, inner parts of the ULIGs, it is quite unlikely that the inner parts are powered by the starburst while the outer parts are powered by non-stellar ionization sources. The most probable resolution of this dilemma is that the optical emission-line nebulae with the LINER properties are powered predominantly by shock heating driven by the superwind activity; i.e., a blast wave driven by a collective effect of a large number of supernovae in the central region of galaxy mergers.Comment: 15 pages, 2 tables, and 3 eps figures. The Astrophysical Journal (Part 1), in pres