Weighted cohomology of arithmetic groups

M. Goresky, G. Harder, and R. MacPherson defined weighted cohomologies of arithmetic groups \Gamma in a real group G, with coefficients in certain local systems, associated to arbitrary upper and lower weight profiles. The author shows, using essentially local arguments on the reductive Borel-Serre compactification, that these cohomologies agree with certain weighted L^2 cohomologies defined by J. Franke. When the rank of G is equal to that of a maximal compact subgroup, this implies that the cohomologies associated to both upper and lower middle profiles are both isomorphic to L^2 cohomology.Comment: 32 pages, published version, abstract added in migratio

A Statistical Model of Current Loops and Magnetic Monopoles

We formulate a natural model of current loops and magnetic monopoles for arbitrary planar graphs, which we call the monopole-dimer model, and express the partition function of this model as a determinant. We then extend the method of Kasteleyn and Temperley-Fisher to calculate the partition function exactly in the case of rectangular grids. This partition function turns out to be a square of the partition function of an emergent monomer-dimer model when the grid sizes are even. We use this formula to calculate the local monopole density, free energy and entropy exactly. Our technique is a novel determinantal formula for the partition function of a model of vertices and loops for arbitrary graphs.Comment: 17 pages, 5 figures, significant stylistic revisions. In particular, rewritten with a mathematical audience in mind. Numerous errors fixed. This is the final published version. Maple program file can be downloaded from the link on the right of this pag

Heavy Scalar, Vector and Axial-Vector Mesons in Hot and Dense Nuclear Medium

In this work we shall investigate the mass modifications of scalar mesons $\left( D_{0}, B_{0}\right)$,vector mesons $\left( D^{\ast}, B^{\ast}\right)$ and axial-vector mesons $\left(D_{1}, B_{1}\right)$ at finite density and temperature of the nuclear medium. The above mesons are modified in the nuclear medium through themodification of quark and gluon condensates. We shall find the medium modification of quark and gluon condensates within chiral SU(3) model through the medium modification of scalar-isoscalar fields $\sigma$ and $\zeta$ at finite density and temperature. These medium modified quark and gluon condensates will further be used through QCD sum rules for the evaluation of in-medium properties of above mentioned scalar, vector and axial vector mesons. We shall also discuss the effects of density and temperature of the nuclear medium on the scattering lengths of above scalar, vector and axial-vector mesons. The study of the medium modifications of above mesons may be helpful for understanding their production rates in heavy-ion collision experiments. The results of present investigations of medium modifications of scalar, vector and axial-vector mesons at finite density and temperature can be verified in the Compressed Baryonic Matter (CBM) experiment of FAIR facility at GSI, Germany.Comment: 35 pages, 11 figure

Full Current Statistics for a Disordered Open Exclusion Process

We consider the nonabelian sandpile model defined on directed trees by Ayyer, Schilling, Steinberg and Thi\'ery (Commun. Math. Phys, 2013) and restrict it to the special case of a one-dimensional lattice of $n$ sites which has open boundaries and disordered hopping rates. We focus on the joint distribution of the integrated currents across each bond simultaneously, and calculate its cumulant generating function exactly. Surprisingly, the process conditioned on seeing specified currents across each bond turns out to be a renormalised version of the same process. We also remark on a duality property of the large deviation function. Lastly, all eigenvalues and both Perron eigenvectors of the tilted generator are determined.Comment: 14 pages, minor clarification

A finite variant of the Toom Model

We present results for a finite variant of the one-dimensional Toom model with closed boundaries. We show that the steady state distribution is not of product form, but is nonetheless simple. In particular, we give explicit formulas for the densities and some nearest neighbour correlation functions. We also give exact results for eigenvalues and multiplicities of the transition matrix using the theory of ${\mathscr R}$-trivial monoids in joint work with A. Schilling, B. Steinberg and N. M. Thi\'ery.Comment: Journal of Physics: Conference Series stylefile, 8 pages, 1 figure; minor changes and clarification