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We associate a quasisymmetric function to any Bruhat interval in a general Coxeter group. This association can be seen to be a morphism of Hopf algebras to the subalgebra of all peak functions, leading to an extension of the cd-index of…

Combinatorics · Mathematics 2009-10-20 Louis J. Billera , Francesco Brenti

The $n$-dimensional lattice polytopes $\mathcal{Q}_{n,k}$ obtained by intersecting the $n$th dilate of the standard $n$-dimensional simplex in $\mathbb{R}^n$ with the half-spaces $x_i \le 1$ for $1 \le i \le k$ form an interesting special…

Combinatorics · Mathematics 2026-03-13 Christos A. Athanasiadis , Qiqi Xiao , Xue Yan

By the work of J.Huh, one can interpret binomial coefficients as a solution to an intersection problem on a permutohedral variety $X_E$. Applying Hirzebruch-Riemann-Roch, this intersection problem is equivalent to computing Euler…

Algebraic Geometry · Mathematics 2025-10-16 Vincenzo Galgano , Hanieh Keneshlou , Mateusz Michalek

We classify the three-dimensional lattice polytopes with two interior lattice points. Up to unimodular equivalence there are 22,673,449 such polytopes. This classification allows us to verify, for this case only, a conjectural upper bound…

Combinatorics · Mathematics 2016-12-30 Gabriele Balletti , Alexander M. Kasprzyk

We introduce a novel intrinsic volume concept in tropical geometry. This is achieved by developing the foundations of a tropical analog of lattice point counting in polytopes. We exhibit the basic properties and compare it to existing…

Metric Geometry · Mathematics 2019-08-22 Georg Loho , Matthias Schymura

Graded Ehrhart theory is a new $q$-analogue of Ehrhart theory based on the orbit harmonics method. We study the graded Ehrhart theory of unimodular zonotopes from a matroid-theoretic perspective. Generalizing a result of Stanley (1991), we…

Combinatorics · Mathematics 2026-03-10 Colin Crowley , Ethan Partida

For a finite volume geodesic polyhedron P in hyperbolic 3-space, with the property that all interior angles between incident faces are integral submultiples of Pi, there is a naturally associated Coxeter group generated by reflections in…

K-Theory and Homology · Mathematics 2017-05-24 J. -F. Lafont , B. A. Magurn , I. J. Ortiz

We describe a family of shellings for the canonical triangulation of the order polytope of the zig-zag poset. This gives a new combinatorial interpretation for the coefficients in the numerator of the Ehrhart series of this order polytopein…

Combinatorics · Mathematics 2020-04-02 Jane Ivy Coons , Seth Sullivant

Let W be a finite Coxeter group. We define its Hecke-group algebra by gluing together appropriately its group algebra and its 0-Hecke algebra. We describe in detail this algebra (dimension, several bases, conjectural presentation,…

Representation Theory · Mathematics 2008-11-20 Florent Hivert , Nicolas M. Thiéry

We study the Ehrhart theory of hypersimplices of type C, as introduced by Lam and Postnikov for general crystallographic root systems. The $h^*$-polynomials of classical hypersimplices are known to relate to various Eulerian statistics on…

Combinatorics · Mathematics 2025-04-08 Antoine Abram , Jose Bastidas

In the article we develop Euler-Lagrange method and calculate all the roots of an arbitrary complex polynomial $P(z)$ on the base of calculation (similar to the Bernoulli-Aitken-Nikiporets methods) of the limits of ratios of Hadamard…

Classical Analysis and ODEs · Mathematics 2023-04-12 M. M. Chernyavskij , A. V. Lebedev , Yu. V. Trubnikov

Let $(W,S,L)$ be a weighted Coxeter system and $J$ a subset of $S$, Yin [12] introduced the weighted $W$-graph ideal $E_J$ and the weighted Kazhdan-Lusztig polynomials $ \left \{ P_{x,y} \mid x,y\in E_J\right \}$. In this paper, we study…

Representation Theory · Mathematics 2019-09-20 Qi Wang

V. Golyshev conjectured that for any smooth polytope P of dimension at most five, the roots $z\in\C$ of the Ehrhart polynomial for P have real part equal to -1/2. An elementary proof is given, and in each dimension the roots are described…

Combinatorics · Mathematics 2012-12-21 Gábor Hegedüs , Alexander M. Kasprzyk

We give two new constructions of the harmonic algebra of a lattice polytope $P$, a bigraded algebra whose character is the $q$-Ehrhart series of $P$ defined by Reiner and Rhoades. First, we show that the harmonic algebra is the associated…

Combinatorics · Mathematics 2025-08-27 Ian Cavey

Brion's Formula realizes the Laurent polynomial of lattice points in a lattice polytope P as the sum of rational functions associated to the vertices of P. In this paper, we consider the special case where P is a generalized permutohedron.…

Combinatorics · Mathematics 2026-05-06 Matthias Beck , Caroline Klivans , Dustin Ross

A polynomial has saturated Newton polytope (SNP) if every lattice point of the convex hull of its exponent vectors corresponds to a monomial. We compile instances of SNP in algebraic combinatorics (some with proofs, others conjecturally):…

Combinatorics · Mathematics 2019-12-03 Cara Monical , Neriman Tokcan , Alexander Yong

We introduce the definition of an Ehrhart limit, that is, a formal power series with integer coefficients that is the limit in the ring of formal power series of a sequence of Ehrhart $h^*$-polynomials. We identify a variety of examples of…

Combinatorics · Mathematics 2022-12-13 Benjamin Braun , McCabe Olsen

Let u and v be permutations on n letters, with u <= v in Bruhat order. A Bruhat interval polytope Q_{u,v} is the convex hull of all permutation vectors z = (z(1), z(2),...,z(n)) with u <= z <= v. Note that when u=e and v=w_0 are the…

Combinatorics · Mathematics 2015-06-11 Emmanuel Tsukerman , Lauren Williams

It was observed by Bump et al. that Ehrhart polynomials in a special family exhibit properties similar to the Riemann {\zeta} function. The construction was generalized by Matsui et al. to a larger family of reflexive polytopes coming from…

Combinatorics · Mathematics 2018-04-20 Akihiro Higashitani , Mario Kummer , Mateusz Michałek

For an arbitrary cocompact hyperbolic Coxeter group G with finite generator set S and complete growth function P(x)/Q(x), we provide a recursion formula for the coefficients of the denominator polynomial Q(x) which allows to determine…

Metric Geometry · Mathematics 2010-06-24 Ruth Kellerhals , Genevieve Perren