Analysis of computing Gr\"obner bases and Gr\"obner degenerations via theory of signatures

Abstract

The signatures of polynomials were originally introduced by Faug\`{e}re for the efficient computation of Gr\"obner bases [Fau02], and redefined by Arri-Perry [AP11] as the standard monomials modulo the module of syzygies. Since it is difficult to determine signatures, Vaccon-Yokoyama [VY17] introduced an alternative object called guessed signatures. In this paper, we consider a module $\mathrm{Gobs}(F)$ for a tuple of polynomials $F$ to analyse computation of Gr\"obner bases via theory of signatures. This is the residue module $\mathrm{ini}_{\prec}(\mathrm{Syz}(\mathrm{LM}(F)))/\mathrm{ini}_{\prec}(\mathrm{Syz}(F))$ defined by the initial modules of the syzygy modules with respect to the Schreyer order. We first show that $F$ is a Gr\"obner basis if and only if $\mathrm{Gobs}(F)$ is the zero module. Then we show that any homogeneous Gr\"obner basis with respect to a graded term order satisfying a common condition must contain the remainder of a reduction of an S-polynomial. We give computational examples of transitions of minimal free resolutions of $\mathrm{Gobs}(F)$ in a signature based algorithm. Finally, we show a connection between the module $\mathrm{Gobs}(F)$ and Gr\"obner degenerations.