We study mediation of supersymmetry breaking in the bulk, in models with primordial supersymmetry breaking on D-branes at the string scale, in the TeV region. We compute the gravitino and scalar masses up to one-loop level, as well as the radion coupling to matter. We find that the latter mediates a model independent force at sub-millimeter distances that… (More)
We study a class of type I string models with supersymmetry broken on the world-volume of some D-branes and vanishing tree-level potential. Despite the non-supersymmetric spectrum, supersymmetry is non-linearly realized on these D-branes, while it is spontaneously broken in the bulk by Scherk-Schwarz boundary conditions. These models can easily accommodate… (More)
We compute the tree-level four-point scattering amplitudes in string models where matter fields live on D-brane intersections. Extracting the contribution of massless modes, we are left with dimension-six four-fermion operators which in general receive contributions from three different sources: exchange of massive Kaluza–Klein excitations, winding modes… (More)
Data networks are subject to congestion, thereby the delay to go across the network may be large enough in order to dishearten customers to keep on using such a network. In this paper we address the problem of determining in a given network a routing which minimizes the delay or keeps it under a certain bound. This problem was already shown as N P complete.… (More)
Given a bidirected ring with capacities and a demand graph, we present an approximation algorithm to the problem of finding the minimum α such that there exists a feasible unsplittable routing of the demands after multiplying each capacity by α. We also give an approximation scheme to the problem.