Ehrhart quasi-polynomials of rational polytopes by real dilations

Fuente: arXiv
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Autori principali: Cao, Ying, Chen, Beifang
Natura: Preprint
Pubblicazione: 2026
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author Cao, Ying
Chen, Beifang
author_facet Cao, Ying
Chen, Beifang
contents This paper is to study the Ehrhart function $L(P,t)$ of a rational $n$-polytope $P$, defined as the number of lattice points of dilated polytopes $tP$ with real numbers $t\geq 0$. It turns out that $L(P,t)$ is a quasi-polynomial of real variable $t$ in the sense that \[ L(P,t)=\sum_{k=0}^{n} c_k(P,t)t^k, \quad t\geq 0, \] where $c_k(P,t)$ are periodic piecewise polynomials of degree $n-k$ if ${\rm aff}\,P$ contains the origin, and are periodic functions vanishing almost everywhere otherwise. When $P$ is a rational simplex $σ$, the coefficient functions $c_k(σ,t)$ are given explicitly in terms of vertex information of the simplex $σ$. Moreover, the reciprocity law still holds.
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id arxiv_https___arxiv_org_abs_2605_10514
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Ehrhart quasi-polynomials of rational polytopes by real dilations
Cao, Ying
Chen, Beifang
Combinatorics
This paper is to study the Ehrhart function $L(P,t)$ of a rational $n$-polytope $P$, defined as the number of lattice points of dilated polytopes $tP$ with real numbers $t\geq 0$. It turns out that $L(P,t)$ is a quasi-polynomial of real variable $t$ in the sense that \[ L(P,t)=\sum_{k=0}^{n} c_k(P,t)t^k, \quad t\geq 0, \] where $c_k(P,t)$ are periodic piecewise polynomials of degree $n-k$ if ${\rm aff}\,P$ contains the origin, and are periodic functions vanishing almost everywhere otherwise. When $P$ is a rational simplex $σ$, the coefficient functions $c_k(σ,t)$ are given explicitly in terms of vertex information of the simplex $σ$. Moreover, the reciprocity law still holds.
title Ehrhart quasi-polynomials of rational polytopes by real dilations
topic Combinatorics
url https://arxiv.org/abs/2605.10514