A finite cover for coefficient positivity of stretched Littlewood-Richardson polynomials in the seven-row, size-thirty box

Abstract

We give a finite cover argument for nonnegativity of the ordinary monomial coefficients of every stretched Littlewood-Richardson polynomial with partition lengths at most seven and outer size at most thirty. Explicit reductions leave 358,952 residual triples. The computational part consists of exact finite enumeration, local reduction checks and rational Ehrhart polynomial computations. Its three named dependencies are stated precisely below, separately from the mathematical implication they establish.

19 pages. Code and computational evidence: https://github.com/chesshippo/stretched-lr-coefficients