Enumerative combinatorics
Enumeration of functions from posets to chains
European Journal of Combinatorics
Actions on permutations and unimodality of descent polynomials
European Journal of Combinatorics
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We refine a technique used in a paper by Schur on real-rooted polynomials. This amounts to an extension of a theorem of Wagner on Hadamard products of Pólya frequency sequences. We also apply our results to polynomials for which the Neggers-Stanley Conjecture is known to hold. More precisely, we settle interlacing properties for E-polynomials of series-parallel posets and column-strict labelled Ferrers posets.