Complete homogeneous symmetric polynomials with repeating variables

Abstract

We consider polynomials of the form $h_m(y_1^{[{\varkappa }_1]},\dots ,y_n^{[{\varkappa }_n]})$, where $h_m$ is the complete homogeneous polynomial of degree $m$ and $y_j^{[{\varkappa }_j]}$ denotes $y_j$ repeated ${\varkappa }_j$ times. Using the decomposition of the generating function into partial fractions we represent such polynomials in the form \[ \operatorname{h}_m(y_1^{[\varkappa_1]},\ldots,y_n^{[\varkappa_n]}) =\sum_{j=1}^n \sum_{r=1}^{\varkappa_j} \binom{r+m-1}{r-1} A_{y,\varkappa,j,r} y_j^m, \] where $A_{y,\varkappa ,j,r}$ are some coefficients that do not depend on $m$. We also provide an alternative proof using the inverse of the confluent Vandermonde matrix.

28 pages