Early's winding-number formula for the Ehrhart h*-vector of the hypersimplex

A decorated ordered set partition consists of an ordered partition of [n][n] whose blocks are decorated by positive integers; it is hypersimplicial of type (k,n)(k,n) when each block LiL_i with decoration lil_i satisfies 1liLi11\leq l_i\leq |L_i|-1. The winding number is the integer dd determined by the total clockwise path length, namely

w1++wn=kd,w_1+\cdots+w_n=kd,

where wiw_i is the clockwise distance from the block containing ii to the block containing (i+1)(i+1), with indices taken modulo nn.

Early's conjecture. The number of hypersimplicial decorated ordered set partitions of type (k,n)(k,n) with winding number dd is hd(Δk,n)h^{*}_d(\Delta_{k,n}).

This gives a combinatorial interpretation of the Ehrhart hh^{*}-vector of the hypersimplex Δk,n\Delta_{k,n}. The supplied source does not state whether the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Donghyun Kim, “A combinatorial formula for the Ehrhart h^*-vector of the hypersimplex”, arXiv:1810.02255 (2020).

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