Many mathematical models concerning for example field calculations, flow simulation, elasticity or visualization are based on operator equations with
boundary integral operators
. Discretizing such problems will then lead in general to possibly very large linear systems with
matrices. Moreover, the involved operator may have an order different from zero which means that it acts on different length scales in a different way. This is well known to entail the linear systems to become more and more ill-conditioned when the level of resolution increases. Both features pose serious obstructions to the efficient numerical treatment of such problems to an extent that desirable realistic simulations are still beyond current computing capacities.