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INTERMEDIATE SUMS ON POLYHEDRA II: BIDEGREE AND POISSON FORMULA

Published online by Cambridge University Press:  29 February 2016

Velleda Baldoni
Affiliation:
Dipartimento di Matematica, Università degli studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, I-00133 Roma, Italy email baldoni@mat.uniroma2.it
Nicole Berline
Affiliation:
École Polytechnique, Centre de Mathématiques Laurent Schwartz, 91128 Palaiseau Cedex, France email Nicole.Berline@math.cnrs.fr
Jesús A. De Loera
Affiliation:
Department of Mathematics, University of California, Davis, One Shields Avenue, Davis, CA 95616, U.S.A. email deloera@math.ucdavis.edu
Matthias Köppe
Affiliation:
Department of Mathematics, University of California, Davis, One Shields Avenue, Davis, CA 95616, U.S.A. email mkoeppe@math.ucdavis.edu
Michèle Vergne
Affiliation:
Institut de Mathématiques de Jussieu – Paris Rive Gauche, Batiment Sophie Germain, Case 7012, 75205 Paris Cedex 13, France email michele.vergne@imj-prg.fr
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Abstract

We continue our study of intermediate sums over polyhedra, interpolating between integrals and discrete sums, which were introduced by Barvinok [Computing the Ehrhart quasi-polynomial of a rational simplex. Math. Comp75 (2006), 1449–1466]. By well-known decompositions, it is sufficient to consider the case of affine cones $s+\mathfrak{c}$, where $s$ is an arbitrary real vertex and $\mathfrak{c}$ is a rational polyhedral cone. For a given rational subspace $L$, we define the intermediate generating functions $S^{L}(s+\mathfrak{c})(\unicode[STIX]{x1D709})$ by integrating an exponential function over all lattice slices of the affine cone $s+\mathfrak{c}$ parallel to the subspace $L$ and summing up the integrals. We expose the bidegree structure in parameters $s$ and $\unicode[STIX]{x1D709}$, which was implicitly used in the algorithms in our papers [Computation of the highest coefficients of weighted Ehrhart quasi-polynomials of rational polyhedra. Found. Comput. Math.12 (2012), 435–469] and [Intermediate sums on polyhedra: computation and real Ehrhart theory. Mathematika59 (2013), 1–22]. The bidegree structure is key to a new proof for the Baldoni–Berline–Vergne approximation theorem for discrete generating functions [Local Euler–Maclaurin expansion of Barvinok valuations and Ehrhart coefficients of rational polytopes. Contemp. Math.452 (2008), 15–33], using the Fourier analysis with respect to the parameter $s$ and a continuity argument. Our study also enables a forthcoming paper, in which we study intermediate sums over multi-parameter families of polytopes.

Type
Research Article
Copyright
Copyright © University College London 2016 

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References

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