Multivariate Meixner polynomials as Birth and Death polynomials

Abstract: Based on the framework of Plamen Iliev, multivariate Meixner polynomials are constructed explicitly as Birth and Death polynomials. They form the complete set of eigenpolynomials of a birth and death process with the birth and death rates at population $x=(x_1,\ldots,x_n)\in\mathbb{N}0^n$ are $B_j(x)=\bigl(\beta+\sum{i=1}^nx_j\bigr)$ and $D_j(x)=c_j^{-1}x_j$, $0<c_j$, $j=1,\ldots,n$, $\sum_{j=1}^nc_j<1$. The corresponding stationary distribution is $(\beta){\sum{j=1}^nc_j}\prod_{j=1}^n(c_j^{x_j}/x_j!)(1-\sum_{j=1}^nc_j)^\beta$, the trivial $n$-variable generalisation of the orthogonality weight of the single variable Meixner polynomials. The polynomials, depending on $n+1$ parameters (${c_i}$ and $\beta$), satisfy the difference equation with the coefficients $B_j(x)$ and $D_j(x)$ $j=1,\ldots,n$, which is the straightforward generalisation of the difference equation governing the single variable Meixner polynomials. The polynomials are truncated $(n+1,2n+2)$ hypergeometric functions of Aomoto-Gelfand. The polynomials and the derivation are very similar to those of the multivariate Krawtchouk polynomials reported recently.