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arXiv · 1108.2852

Enumerative $g$-theorems for the Veronese construction for formal power series and graded algebras

Martina Kubitzke·Volkmar Welker
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Abstract

Let $(a_n)_{n \geq 0}$ be a sequence of integers such that its generating series satisfies $\sum_{n \geq 0} a_nt^n = \frac{h(t)}{(1-t)^d}$ for some polynomial $h(t)$. For any $r \geq 1$ we study the coefficient sequence of the numerator polynomial $h_0(a^{ }) +...+ h_{\lambda'}(a^{ }) t^{\lambda'}$ of the $r$\textsuperscript{th} Veronese series $a^{ }(t) = \sum_{n \geq 0} a_{nr} t^n$. Under mild hypothesis we show that the vector of successive differences of this sequence up to the $\lfloor \frac{d}{2} \rfloor$\textsuperscript{th} entry is the $f$-vector of a simplicial complex for large $r$. In particular, the sequence satisfies the consequences of the unimodality part of the $g$-conjecture. We give applications of the main result to Hilbert series of Veronese algebras of standard graded algebras and the $f$-vectors of edgewise subdivisions of simplicial complexes.

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Martina Kubitzke, Volkmar Welker. 2011-08-14. Enumerative $g$-theorems for the Veronese construction for formal power series and graded algebras. https://arxiv.org/abs/1108.2852

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