On partially matchable subspaces in a field extension

Abstract

We formulate and prove linear counterparts of results on partial matchings between finite subsets in abelian groups. In the group setting, there are necessary and sufficient criteria for the existence of partial matchings under suitable hypotheses; our aim is to obtain parallel statements in a linear framework. In particular, for a field extension $K\subsetneq L$ we introduce a notion of partial matching between finite-dimensional $K$-subspaces $A,B\subseteq L$, and we prove existence theorems mirroring known results for subsets of abelian groups. Along the way, we recover and extend various parts of this area of matching theory, emphasizing the close analogy between the group-theoretic and linear settings. Our approach blends classical linear-algebraic techniques with tools from matroidal transversal theory, and utilizes a linearized version of a method originating in additive number theory.