The winding-number conjecture for generic cube cross-section h*-vectors

Fix integers r,nr,n and ss with 1srn11\le s\le rn-1, and let

Ir,sn={x[0,r]n:i=1nxi=s}.I_{r,s}^n=\left\{x\in[0,r]^n:\sum_{i=1}^n x_i=s\right\}.

Consider decorated ordered set partitions ((L1)l1,,(Lk)lk)((L_1)_{l_1},\ldots,(L_k)_{l_k}) with 1L11\in L_1, satisfying

l1++lk=s,1lirLi1.l_1+\cdots+l_k=s,\qquad 1\le l_i\le r|L_i|-1.

Let wPw_P be the winding number, and denote by m0,m1,m_0,m_1,\ldots the numbers of these partitions having winding numbers wP=0,1,2,w_P=0,1,2,\ldots. The cube-cross-section winding-number conjecture. The vector (m0,m1,)(m_0,m_1,\ldots) equals the Ehrhart hh^*-vector of the hyperplane cross-section Ir,snI_{r,s}^n. This would provide a combinatorial interpretation of the hh^*-vectors of integer-sum hyperplane cross-sections of cubes; the source presents it as an additional conjectural extension of the hypersimplex and dilated-simplex cases.

Sources & referencesView supporting material

Primary source

Nick Early, “Conjectures for Ehrhart h^*-vectors of Hypersimplices and Dilated Simplices”, arXiv:1710.09507 (2017).

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