A direct proof of dimerization in a family of SU(n)-invariant quantum spin chains

We study the family of spin-S quantum spin chains with a nearest neighbor interaction given by the negative of the singlet projection operator. Using a random loop representation of the partition function in the limit of zero temperature and standard techniques of classical statistical mechanics, we prove dimerization for all sufficiently large values of S.Comment: 14 pages, 7 figures, updated to published version and one footnote adde

How Government Bond Prices Reflect Wartime Events. The Case of the Stockholm Market.

How are political events reflected in financial asset prices? Break points in sovereign debt prices are analyzed for Denmark, Norway, Finland, Sweden, Germany and Belgium during 1930-1948, using unique data from the Stockholm Stock Exchange. Unlike in countries involved in WWII, this market was unregulated. The outbreak of World War II heavily depressed prices of government bonds. Countries which were occupied (Belgium, Denmark and Norway) or under attack (Finland) saw their debt depreciate substantially. The battle of Stalingrad turns out indeed to be a turning-point of the war. This approach represents a complementary quantitative method to analyze the impact of political events.Financial Markets; Economic History; WWII; Europe; Cliometrics

Amplification of the Signal-to-Noise Ratio in Cosmic Ray Maps Using the Mexican Hat Wavelet Family

In this work we analyze the effect of smoothing maps containing arrival directions of cosmic rays with a gaussian kernel and kernels of the mexican hat wavelets of orders 1, 2 and 3. The analysis is performed by calculating the amplification of the signal-to-noise ratio for several background patterns (noise) and different number of events coming from a simulated source (signal) for an ideal detector capable of observing the full sky with uniform coverage. We extend this analysis for a virtual observatory with two sites, one in the northern hemisphere, the other in the southern, considering an acceptance law.Comment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201

Eigenvalues estimate for the Neumann problem on bounded domains

In this note, we investigate upper bounds of the Neumann eigenvalue problem for the Laplacian of a bounded domain (with smooth boundary) in a given complete (not compact a priori) Riemannian manifold with Ricci bounded below . For this, we use test functions for the Rayleigh quotient subordinated to a family of open sets constructed in a general metric way, interesting for itself. As application, we get upper bounds for the Neumann spectrum which is clearly in agreement with the Weyl law and which is analogous to Buser's upper bounds of the spectrum of a closed Riemannian manifold with lower bound on the Ricci curvature.Comment: 9 pages, submitted december 200

Forest influence on the surface water chemistry of granitic basins receiving acid precipitation in the Vosges massif, France

This study shows the influence of acid rain on the chemistry of surface waters in two small basins. The basins present similar altitudes and climates, only one is forested, and the forest decline has been clearly established. In both basins, rain water is polluted by acids (H+, so24-,N03). This acid input is neutralized in soils but the efficiency of that neutralization varies from one basin to another: (a) in the non forested basin, the alkalinity of surface water dominates the anionic charge, (b) in the forested basin, the strong acid anions still dominate the anionic charge of a just neutralized solution. The chemistry of surface water in the forested basin cannot be explained only by the incident rainfall and its partial evaporation. There appears to be a major input of pollutant through dry deposits in throughfall

Proton transfer in histidine-tryptophan heterodimers embedded in helium droplets

We used cold helium droplets as nano-scale reactors to form and ionize, by electron bombardment and charge transfer, aromatic amino acid heterodimers of histidine with tryptophan, methyl-tryptophan, and indole. The molecular interaction occurring through an N-H...N hydrogen bond leads to a proton transfer from the indole group of tryptophan to the imidazole group of histidine in a radical cationic environment