Nonlinear and spin-glass susceptibilities of three site-diluted systems

The nonlinear magnetic $\chi_{3}$ and spin-glass $\chi_{sg}$ susceptibilities in zero applied field are obtained, from tempered Monte Carlo simulations, for three different spin glasses (SGs) of Ising spins with quenched site disorder. We find that the relation $-T^3\chi_3=\chi_{sg}-2/3$ ($T$ is the temperature), which holds for Edwards-Anderson SGs, is approximately fulfilled in canonical-like SGs. For nearest neighbor antiferromagnetic interactions, on a 0.4 fraction of all sites in fcc lattices, as well as for spatially disordered Ising dipolar (DID) systems, $-T^3\chi_3$ and $\chi_{sg}$ appear to diverge in the same manner at the critical temperature $T_{sg}$. However, $-T^3\chi_3$ is smaller than $\chi_{sg}$ by over two orders of magnitude in the diluted fcc system. In DID systems, $-T^3\chi_3/\chi_{sg}$ is very sensitive to the systems aspect ratio. Whereas near $T_{sg}$, $\chi_{sg}$ varies by approximately a factor of 2 as system shape varies from cubic to long-thin-needle shapes, $\chi_3$ sweeps over some four decades.Comment: 7 pages, 7 figure

Time relaxation of interacting single--molecule magnets

We study the relaxation of interacting single--molecule magnets (SMMs) in both spatially ordered and disordered systems. The tunneling window is assumed to be, as in Fe8, much narrower than the dipolar field spread. We show that relaxation in disordered systems differs qualitatively from relaxation in fully occupied cubic and Fe_8 lattices. We also study how line shapes that develop in ''hole--digging'' experiments evolve with time t in these fully occupied lattices. We show (1) that the dipolar field h scales as t^p in these hole line shapes and show (2) how p varies with lattice structure. Line shapes are not, in general, Lorentzian. More specifically, in the lower portion of the hole, they behave as (h/t^p)^{(1/p)-1} if h is outside the tunnel window. This is in agreement with experiment and with our own Monte Carlo results.Comment: 21 LaTeX pages, 6 eps figures. Submitted to PRB on 15 June 2005. Accepted on 13 August 200

Magnetization Process of Single Molecule Magnets at Low Temperatures

We show that correlations established before quenching to very low temperatures, later drive the magnetization process of systems of single molecule magnets, after a magnetic field is applied at t=0. We also show that in SC lattices, m \propto sqrt(t), as observed in Fe_8, but only for 1+2*log_10(h_d/h_w) time decades, where h_d is a nearest neighbor dipolar magnetic field and a spin reversal can occur only if the field on it is within (-h_w,h_w). However, the sqrt(t) behavior is not universal. For BCC and FCC lattices, m \propto t^p, but p \simeq 0.7. The value to which m finally levels off is also given.Comment: 5 LaTeX pages, 2 figures. Submitted to Phys. Rev. Lett. on 26 January 2003, accepted on 24 July 200

Continuous spin reorientation in antiferromagnetic films

We study anisotropic antiferromagnetic one-layer films with dipolar and nearest-neighbor exchange interactions. We obtain a unified phase diagram as a function of effective uniaxial D_e and quadrupolar C anisotropy constants. We study in some detail how spins reorient continuously below a temperature T_s as T and D_e vary.Comment: 3 LaTeX pages, 3 eps figures. Submitted to JMMM on 25 May 2006. Accepted on 21 July 200

A note on the computation of the Frobenius number of a numerical semigroup

In this note we observe that the Frobenius number and therefore the conductor of a numerical semigroup can be obtained from the maximal socle degree of the quotient of the corresponding semigroup algebra by the ideal generated by the biggest generator of the semigroup.Comment: Some typos in the introduction have been correcte

LAS PLATAFORMAS DIGITALES EN EL DESARROLLO DEL ENOTURISMO EN CASTILLA Y LEÓN: PÁGINAS WEB Y REDES SOCIALES

Wine tourism is a growing economic activity in Castilla y León. More and more people are interested in knowing the ins and outs of the world of wine, so wine is becoming one of the pillars of rural development in the plains of the Duero. In order to achieve this key role in the territory, this activity has had to adapt to changes in the tastes of consumers and, especially, to faster and more direct new forms of communication. This paper aims to outlook the existing situation in the wineries of Castilla y León in the field of new technologies and, especially, of websites and social networks, two key tools for the development of wine tourism.El enoturismo es una actividad económica en crecimiento en Castilla y León. Cada vez son más las personas interesadas en conocer el mundo de la vid y el vino, convirtiéndose en uno de los pilares del desarrollo rural en las llanuras del Duero. Para lograr este papel clave en el territorio, esta actividad ha tenido que adaptarse a los cambios en los gustos de los consumidores y, en especial, a las nuevas formas de comunicación digital, más rápidas y directas. Con este trabajo se pretende ver la situación existente en las bodegas castellano-leonesas en el ámbito de las nuevas tecnologías y, en especial, de las páginas web y redes sociales, dos herramientas claves para el desarrollo del turismo enológico

EL CANAL DE CASTILLA: RECURSO PATRIMONIAL DEL AGUA Y PERSPECTIVAS DE USO E INNOVACIÓN TURÍSTICA

Castile and León has important resources that allow tourism development, such as the Castilla Canal, a hydraulic infrastructure that has become a key element of the Spanish industrial heritage of the 18th-19th centuries. This research analyzes the Castilla Canal as a tourist resource and its level of innovation as a smart tourism destination, where communication technologies play a key role in the management and planning of available resources, in a territory that is in a regression socioeconomic status for decades.Castilla y León cuenta con importantes recursos que permiten el desarrollo turístico, como el Canal de Castilla, una infraestructura hidráulica que se ha convertido en un elemento clave del patrimonio industrial español de los siglos XVIII-XIX. En esta investigación se analiza el Canal de Castilla como recurso turístico y su nivel de innovación como destino de turismo inteligente, donde las tecnologías de la comunicación juegan un papel clave en la gestión y planificación de los recursos disponibles, en un territorio que se encuentra en regresión socioeconómica desde hace décadas