Phase transitions and symmetry energy in nuclear pasta

Cold and isospin-symmetric nuclear matter at sub-saturation densities is known to form the so-called pasta structures, which, in turn, are known to undergo peculiar phase transitions. Here we investigate if such pastas and their phase changes survive in isospin asymmetric nuclear matter, and whether the symmetry energy of such pasta configurations is connected to the isospin content, the morphology of the pasta and to the phase transitions. We find that indeed pastas are formed in isospin asymmetric systems with proton to neutron ratios of x = 0.3, 0.4 and 0.5, densities in the range of 0.05 fm−3 the morphology of the nuclear matter structure.Fil: Dorso, Claudio Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Frank, Guillermo Alberto. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: López, Jorge A.. University of Texas at El Paso; Estados Unido

Strong asymptotics for the Pollaczek multiple orthogonal polynomials

The asymptotic properties of multiple orthogonal polynomials with respect to two Pollaczek weights with different parameters are considered. This set of weights is a Nikishin system generated by two measures with unbounded supports; moreover, the second measure is discrete. During the last years, multiple orthogonal polynomials with respect to Nikishin systems of this type have found wide applications in the theory of random matrices. Strong asymptotic formulas for the polynomials under consideration are obtained by means of the matrix Riemann-Hilbert method.The first author acknowledges the support of the Rus sian Science Foundation, project no. 14 -21- 00025. The second author’s research was supported by MTM2012 -36732 -C03 -01 MEC. The third author’s research was supported by MTM2011-28952-C02-01 ERDF, Exc. Grant no. P11- FQM -7276, Res. Group FQM -229, and CEIMAR Universidad de Almeria

Properties of nuclear pastas

In this review we study the nuclear pastas as they are expected to be formed in neutron star crusts. We start with a study of the pastas formed in nuclear matter (composed of protons and neutrons), we follow with the role of the electron gas on the formation of pastas, and we then investigate the pastas in neutron star matter (nuclear matter embedded in an electron gas). Nuclear matter (NM) at intermediate temperatures (1 MeV ≲ T ≲ 15 MeV), at saturation and sub-saturation densities, and with proton content ranging from 30% to 50% was found to have liquid, gaseous and liquid-gas mixed phases. The isospin-dependent phase diagram was obtained along with the critical points, and the symmetry energy was calculated and compared to experimental data and other theories. At low temperatures (T ≲ 1 MeV) NM produces crystal-like structures around saturation densities, and pasta-like structures at sub-saturation densities. Properties of the pasta structures were studied with cluster-recognition algorithms, caloric curve, the radial distribution function, the Lindemann coefficient, Kolmogorov statistics, Minkowski functionals; the symmetry energy of the pasta showed a connection with its morphology. Neutron star matter (NSM) is nuclear matter embedded in an electron gas. The electron gas is included in the calculation by the inclusion of an screened Coulomb potential. To connect the NM pastas with those in neutron star matter (NSM), the role the strength and screening length of the Coulomb interaction have on the formation of the pastas in NM was investigated. Pasta was found to exist even without the presence of the electron gas, but the effect of the Coulomb interaction is to form more defined pasta structures, among other effects. Likewise, it was determined that there is a minimal screening length for the developed structures to be independent of the cell size. Neutron star matter was found to have similar phases as NM, phase transitions, symmetry energy, structure function and thermal conductivity. Like in NM, pasta forms at around T ≈ 1.5 MeV, and liquid-to-solid phase changes were detected at T ≈ 0.5 MeV. The structure function and the symmetry energy were also found to depend on the pasta structures.Fil: López, Jorge A.. University of Texas at El Paso; Estados UnidosFil: Dorso, Claudio Oscar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Frank, Guillermo Alberto. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Curvature effects on a simplified reaction-diffusion model of biodegradation

The biodegradation process of some types of polymers occurs due to many different factors including their morphology, structure and chemical composition. Although this is a complicated process, most of its important stages like the diffusion of monomers and the hydrolysis reactions have been modeled phenomenologically through reaction-diffusion equations, where the properties of the polymers were encompassed. Using a simplified reaction-diffusion model for the biodegradation of polymers, in this contribution we study the possible effects of the curvature of the system’s geometry in the degradation process, which is characterized by the interaction of the corresponding reaction rate and the diffusion coefficient. To illustrate the problem of diffusion on a curved surface we consider the surface of a cylinder and of the so-called Gaussian bump. We show how the degradation process is affected by the curvature of the system for the simplified model

Orthogonal polynomials with respect to a differential operator. Existence and uniqueness

15 pages, no figures.-- MSC1991 codes: Primary 42C05.MR#: MR1934900 (2003i:42033)Zbl#: Zbl 1029.42018A new type of orthogonal polynomial connected withlin ear differential operators, intimately related withS obolev orthogonal polynomials and Hermite-Padé polynomials, is introduced. We study the question of uniqueness of the sequence of orthogonal polynomials arising from this construction. As we show, this problem is related to the analytic properties of the fundamental system of solutions of the operator. The notion of T-system of Tchebyshev plays a key role in the analysis. Some examples of general classes of operators which produce a unique system of polynomials are given.The research of the first author (A.I.A.) was supported by grant 93-01278 of the Russian Basic Research Foundation. The research of the second (G.T.L.L.) and third (F.M.) authors was supported by Dirección General de Investigación (Ministerio de Ciencia y Tecnología) of Spain under grant BFM2000-0206-C04-01, and INTAS 2000-272.Publicad

NPB-MPJ: NAS Parallel Benchmarks Implementation for Message-Passing in Java

This is a post-peer-review, pre-copyedit version. The final authenticated version is available online at: http://dx.doi.org/10.1109/PDP.2009.59[Abstract] Java is a valuable and emerging alternative for the development of parallel applications, thanks to the availability of several Java message-passing libraries and its full multithreading support. The combination of both shared and distributed memory programming is an interesting option for parallel programming multi-core systems. However, the concerns about Java performance are hindering its adoption in this field, although it is difficult to evaluate accurately its performance due to the lack of standard benchmarks in Java. This paper presents NPB-MPJ, the first extensive implementation of the NAS Parallel Benchmarks (NPB), the standard parallel benchmark suite, for Message-Passing in Java (MPJ) libraries. Together with the design and implementation details of NPB-MPJ, this paper gathers several optimization techniques that can serve as a guide for the development of more efficient Java applications for High Performance Computing (HPC). NPB-MPJ has been used in the performance evaluation of Java against C/Fortran parallel libraries on two representative multi-core clusters. Thus, NPB-MPJ provides an up-to-date snapshot of MPJ performance, whose comparative analysis of current Java and native parallel solutions confirms that MPJ is an alternative for parallel programming multi-core systems.Ministerio de Educación y Ciencia; TIN2004-07797-C02Ministerio de Educación y Ciencia; TIN2007-67537-C03-02Xunta de Galicia; PGIDIT06PXIB105228P

El factor humano en los conflictos laborales

Fil: López, Guillermo A. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Laboral. Buenos Aires, ArgentinaSumario I - introducción II -de vuelta del "homo economicus" III -origen de las relaciones humanas IV -el grupo laboral V - función social de la empresa VI -actualidad, extensión y orígenes de las relaciones humana

On the limit behavior of recurrence coefficients for multiple orthogonal polynomials

25 pages, no figures.-- MSC1991 codes: primary 42C05, 33C25; secondary 41A21.-- Dedicated to Barry Simon on the occasion of his sixtieth birthday.MR#: MR2220045 (2007a:42048)Zbl#: Zbl 1140.42011In this paper we investigate general properties of the coefficients in the recurrence relation satisfied by multiple orthogonal polynomials. The results include as particular cases Angelesco and Nikishin systems.A. I. Aptekarev, G. López, and V. A. Kalyagin were supported by grants from INTAS 03-516637 and NATO PST.CLG.979738. V. A. Kalyagin and A. I. Aptekarev were supported by grant Scientific Schools 1551.2003.1. A. I. Aptekarev was supported by grants RFBR 02-01-00564, and program N. 1 of the Mathematics Section of the RAS. V. A. Kalyagin received support from RFFI 05-01-00697. G. López and I. A. Rocha were supported by BFM 2003-06335-C03-02.Publicad

A family of Nikishin systems with periodic recurrence coefficients

Suppose we have a Nikishin system of $p$ measures with the $k$th generating measure of the Nikishin system supported on an interval \Delta_k\subset\er with $\Delta_k\cap\Delta_{k+1}=\emptyset$ for all $k$. It is well known that the corresponding staircase sequence of multiple orthogonal polynomials satisfies a $(p+2)$-term recurrence relation whose recurrence coefficients, under appropriate assumptions on the generating measures, have periodic limits of period $p$. (The limit values depend only on the positions of the intervals $\Delta_k$.) Taking these periodic limit values as the coefficients of a new $(p+2)$-term recurrence relation, we construct a canonical sequence of monic polynomials $\{P_{n}\}_{n=0}^{\infty}$, the so-called \emph{Chebyshev-Nikishin polynomials}. We show that the polynomials $P_{n}$ themselves form a sequence of multiple orthogonal polynomials with respect to some Nikishin system of measures, with the $k$th generating measure being absolutely continuous on $\Delta_{k}$. In this way we generalize a result of the third author and Rocha \cite{LopRoc} for the case $p=2$. The proof uses the connection with block Toeplitz matrices, and with a certain Riemann surface of genus zero. We also obtain strong asymptotics and an exact Widom-type formula for the second kind functions of the Nikishin system for $\{P_{n}\}_{n=0}^{\infty}$.Comment: 30 pages, minor change