Knutson, Tao, and Woodward (2004) formulated a Littlewood–Richardson
rule for the cohomology ring of Grassmannians in terms of puzzles.
Vakil (2006) and Wheeler and Zinn-Justin (2017) have found additional
triangular puzzle pieces that allow one to express structure constants for
-theory
of Grassmannians. Here we introduce two other puzzle pieces of
hexagonal shape, each of which gives a Littlewood–Richardson rule for
-homology
of Grassmannians. We also explore the corresponding eight versions of
-theoretic
Littlewood–Richardson tableaux.