Substructuring preconditioners for mortar discretization of a degenerate evolution problem

In this paper we present new efficient variants of substructuring preconditioners for algebraic linear systems arising from the mortar discretization of a degenerate parabolic system of equations. The new approaches extend and adapt the idea of substructuring pre- conditioners to the discretization of a degenerate problem in electrocardiology. A polyloga- rithmic bound for the condition number of the preconditioned matrix is proved and validated by numerical experiments.