In this paper we introduce a variant of the three-field formulation where we use only two sets of variables. Considering, to fix the ideas, the homogeneous Dirichlet problem for −∆u = g in Ω, our variables are i) an approximation ψh of u on the skeleton (the union of the interfaces of the sub-domains) on an independent grid (that could often be uniform), and ii) the approximations uh of u in ea...

This paper introduces a robust preconditioner for general sparse symmetric matrices, that is based on low-rank approximations of the Schur complement in a Domain Decomposition (DD) framework. In this “Schur Low Rank” (SLR) preconditioning approach, the coefficient matrix is first decoupled by DD, and then a low-rank correction is exploited to compute an approximate inverse of the Schur compleme...

The superfluid weight is an important observable of superconducting materials since it related to the London penetration depth Meissner effect. It can be computed from change in grand potential (or free energy) response twisted boundary conditions a torus geometry. Here we review Bardeen-Cooper-Schrieffer mean-field theory emphasizing its origin as variational approximation for potential. param...