Schur positivity of the spiders $S(a,2,1)$ and $S(a,4,1)$ via noncommutative symmetric functions

Jean-Yves Thibon, David G. L. Wang

We prove that the spider graphs $S(a,2,1)$ and $S(a,4,1)$ are Schur positive for all integers $a\ge 1$. Together with the known $e$-positivity results, this completes the $e$- and S…