A Spin - 3/2 Ising Model on a Square Lattice

The spin - 3/2 Ising model on a square lattice is investigated. It is shown that this model is reducible to an eight - vertex model on a surface in the parameter space spanned by coupling constants J, K, L and M. It is shown that this model is equivalent to an exactly solvable free fermion model along two lines in the parameter space.Comment: LaTeX, 7 pages, 1 figure upon request; JETP Letters, in pres

Exact correlation functions of Bethe lattice spin models in external fields

We develop a transfer matrix method to compute exactly the spin-spin correlation functions of Bethe lattice spin models in the external magnetic field h and for any temperature T. We first compute the correlation function for the most general spin - S Ising model, which contains all possible single-ion and nearest-neighbor pair interactions. This general spin - S Ising model includes the spin-1/2 simple Ising model and the Blume-Emery-Griffiths (BEG) model as special cases. From the spin-spin correlation functions, we obtain functions of correlation length for the simple Ising model and BEG model, which show interesting scaling and divergent behavior as T approaches the critical temperature. Our method to compute exact spin-spin correlation functions may be applied to other Ising-type models on Bethe and Bethe-like lattices.Comment: 19 page

Quantum computation based on d-level cluster states

The concept of qudit (a d-level system) cluster state is proposed by generalizing the qubit cluster state (Phys. Rev. Lett. \textbf{86}, 910 (2001)) according to the finite dimensional representations of quantum plane algebra. We demonstrate their quantum correlations and prove a theorem which guarantees the availability of the qudit cluster states in quantum computation. We explicitly construct the network to show the universality of the one-way computer based on the defined qudit cluster states and single-qudit measurement. And the corresponding protocol of implementing one-way quantum computer can be suggested with the high dimensional "Ising" model which can be found in many magnetic systems.Comment: Revtex4, 15 pages, 3 eps figure

Evolution des accidents d'avalanches en France de 1971 à 1994

Since the founding of the ANENA, at the end of 1971, all the heavy avalanche accidents are recorded in France with the maximum of information. The present work treats 857 accidents during the period October 1971 to September 1994. In 23 Winters, more than 2 500 people were recorded caught by avalanches, with 670 killed and 588 injuried. It represents, on average, 37 accidents per year and 30 deaths per year. / Depuis sa création en octobre 1971, l'ANENA enregistre les accidents graves d'avalanches, qui font l'objet d'articles de presse et de déclarations aux organismes publics de secours en montagne (PGHM, CRS des Alpes). Ainsi, entre octobre 1971 et septembre 1994 (soit 23 hivers), 857 accidents (37 par an en moyenne) ont été enregistrés, concernant plus de 2 500 personnes emportées. 1 115 ont été ensevelies, 588 ont été blessées et 670 ont été tuées (soit en moyenne 30 par an)

Blowing snow and avalanches

This paper presents results from a joint research project dedicated to the study of the part played by snowdrift in avalanche occurrence. After a description of the experimental site and the field measurements, some results and tools developed for avalanche forecasting are listed. They deal with snow particle mobility, snow drift occurrence and wind parameters estimation. The paper gives the definition of a snow drift index and presents test and validation procedures on this index. Then the determination of the snow distribution by use of photogrammetry is presented as well as the first results of a symbolic simulation of snowdrift. / Cet article présente des résultats issus d'un projet commun de recherche consacré à l'étude du rôle du transport de neige par le vent dans l'occurrence des avalanches.Après une description du site expérimental et des mesures de terrain, des résultats et des outils développés pour la prévision des avalanches sont détaillés. Ils traitent de la mobilité des particules de neige, de l'occurrence du transport de la neige par le vent et de l'estimation des paramètres du vent. L'article propose une définition d'un index de transport et discute les procédures de test et de validation de cet index. Ensuite, la détermination de la distribution de la neige par l'utilisation de la photogrammétrie est présentée ainsi que les premiers résultats d'une simulation symbolique du transport de neige