Satisfying spin-assignments of triangulations of a surface are states of minimum energy of the antiferromagnetic Ising model on triangulations which correspond (via geometric duality) to perfect matchings in cubic bridgeless graphs. In this work we show that it is NP-complete to decide whether or not a triangulation of a surface admits a satisfying spinassignment, and that it is #P-complete to ...

in this paper, several xed point theorems for t-contraction of two maps on cone metric spaces under normality condition are proved. obtained results extend and generalize well-known comparable results in the literature.

Using the differential-geometric control theory, we present in this note a necessary and sufficient condition under which an affine system is locally feedback equivalent to, via a change of coordinates and restricted smooth state feedback, a generalized normal form called —normal form, which includes Brunovsky canonical form and feedback linearizable systems in a lower-triangular form as its sp...