Grobner Basis over Semigroup Algebras: Algorithms and Applications for Sparse Polynomial Systems

Grobner bases is one the most powerful tools in algorithmic nonlinear algebra. Their computation is an intrinsically hard problem with a complexity at least single exponential in the number of variables. However, in most of the cases, the polynomial systems coming from applications have some kind of structure. We consider sparse systems where the input polynomials have a few non-zero terms. Our approach to exploit sparsity is to embed the systems in a semigroup algebra and to compute Grobner bases over this algebra. Up to now, the algorithms that follow this approach benefit from the sparsity only in the case where all the polynomials have the same sparsity structure, that is the same Newton polytope. We introduce the first algorithm that overcomes this restriction. Under regularity assumptions, it performs no redundant computations. Further, we extend this algorithm to compute Grobner basis in the standard algebra and solve sparse polynomials systems over the torus (C*)(n). The complexity of the algorithm depends on the Newton polytopes.