Efficient Algorithms for Minimal Matroid Extensions and Irreducible Decompositions of Circuit Varieties

Abstract: We introduce an efficient method for decomposing the circuit variety of a given matroid $M$, based on an algorithm that identifies its minimal extensions. These extensions correspond to the smallest elements above $M$ in the poset defined by the dependency order. We apply our algorithm to several classical configurations: the V\'amos matroid, the unique Steiner quadruple system $S(3,4,8)$, the projective and affine planes, the dual of the Fano matroid, and the dual of the graphic matroid of $K_{3,3}$. In each case, we compute the minimal irreducible decomposition of their circuit varieties.