The algebraic matroid of the funtf variety

Abstract: A finite unit norm tight frame is a collection of $r$ vectors in $\mathbb{R}<sup>n$ that generalizes the notion of orthonormal bases. The affine finite unit norm tight frame variety is the Zariski closure of the set of finite unit norm tight frames. Determining the fiber of a projection of this variety onto a set of coordinates is called the algebraic finite unit norm tight frame completion problem. Our techniques involve the algebraic matroid of an algebraic variety, which encodes the dimensions of fibers of coordinate projections. This work characterizes the bases of the algebraic matroid underlying the variety of finite unit norm tight frames in $\mathbb{R}<sup>3$. Partial results towards similar characterizations for finite unit norm tight frames in $\mathbb{R}<sup>n$ with $n \ge 4$ are also given. We provide a method to bound the degree of the projections based off of combinatorial~data.