Abstract:We give a new proof for a theorem of Ehrhart regarding the quasi-polynomiality of the function that counts the number of integer points in the integral dilates of a rational polytope. The proof involves a geometric bijection, inclusion-exclusion, and recurrence relations, and we also prove Ehrhart reciprocity using these methods.
“…Then P I = i∈I P {i} for all ∅ = I ⊆ [r]. As in [15] we observe that (k + d)∆ d−1 = P ∅ = i∈[d] P {i} for all k ≥ 0. Therefore, by inclusion-exclusion,…”
Section: Characteristic Functions and Valuationsmentioning
confidence: 53%
“…Therefore the order of the minimal polynomial of the sequence is dim P as was demonstrated in [15] and is thus in general smaller than |V(P )|.…”
We consider the integer point transform σPn ] of a polytope P ⊂ R n . We show that if P is a lattice polytope then for any polytope Q the sequence {σ kP +Q (x)} k≥0 satisfies a multivariate linear recursion that only depends on the vertices of P . We recover Brion's Theorem and by applying our results to Schur polynomials we disprove a conjecture of Alexandersson (2014).
“…Then P I = i∈I P {i} for all ∅ = I ⊆ [r]. As in [15] we observe that (k + d)∆ d−1 = P ∅ = i∈[d] P {i} for all k ≥ 0. Therefore, by inclusion-exclusion,…”
Section: Characteristic Functions and Valuationsmentioning
confidence: 53%
“…Therefore the order of the minimal polynomial of the sequence is dim P as was demonstrated in [15] and is thus in general smaller than |V(P )|.…”
We consider the integer point transform σPn ] of a polytope P ⊂ R n . We show that if P is a lattice polytope then for any polytope Q the sequence {σ kP +Q (x)} k≥0 satisfies a multivariate linear recursion that only depends on the vertices of P . We recover Brion's Theorem and by applying our results to Schur polynomials we disprove a conjecture of Alexandersson (2014).
“…A detailed proof following the instructions of [6,Section 3.7] is documented in Barco [5]. (See Sam [90] for an alternative approach.) Note that for any polytope ∆, all the faces in its boundary ∂∆ must be convex.…”
Section: Normal Affine Semigroup Rings and Ehrhart Theorymentioning
We discuss Hilbert-Kunz function from when it was originally defined to its recent developments. A brief history of Hilbert-Kunz theory is first recounted. Then we review several techniques involved in the study of Hilbert-Kunz functions by presenting some illustrative proofs without going into details of the technicalities.The second part of this article focuses on the Hilbert-Kunz function of an affine normal semigroup ring and relates it to Ehrhart quasipolynomials. We pay extra attention to its periodic behavior and discuss how the cellular decomposition constructed by Bruns and Gubeladze fits into the computation of the functions. The closed forms of the Hilbert-Kunz function of some examples are presented. The discussion in this part highlights the close relationship between Hilbert-Kunz function and Ehrhart theory.
“…Lately there has been a lot of literature on various topics generated by the Ehrhart polynomial and we cite just a few papers and books: [1], [2], [3], [4], [5], [6], [7], [8], [9], [11], [28], [29], and [31].…”
In this paper we calculate the Ehrhart's polynomial associated with a 2-dimensional regular polytope (i.e. equilateral triangles) in Z 3 . The polynomial takes a relatively simple form in terms of the coordinates of the vertices of the polytope and it depends heavily on the value d and its divisors, where d = a 2 +b 2 +c 2 3 and (a, b, c) (gcd(a, b, c) = 1) is a vector with integer coordinates normal to the plane containing the triangle.
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