Equispectrality and Transplantation
  We present a technique novel in numerical methods. It compiles the domain of the numerical methods as a discretized volume. Congruent elements are glued together to compile the domain over which the solution of a boundary value problem of a linear operator is sought. We associate a group and a graph to that volume. When the group is symmetry of the boundary value problem under investigation, one can specify the structure of the solution, and find out if there are equispectral volumes of a given type. We show that similarity of the so called auxiliary matrices is sufficient and necessary for two discretized volumes to be equispectral. A simple example demonstrates the feasibility of the suggested method. 
Mikl\'os Antal, Mih\'aly Makai