collaborators

6 papers

math.CO2026

Twisted primitive group association schemes

Akihiro Higashitani, Masanari Kamiya, Hirotake Kurihara

We give results on the question of whether the intersection numbers of a primitive group association scheme determine it up to combinatorial isomorphism. For $G=\operatorname{PSL}(…

math.CO2026

Indecomposability of 0/1-polytopes

Akihiro Higashitani, Arnau Padrol, Raman Sanyal

We prove that every 0/1-polytope has a unique Minkowski decomposition into indecomposable polytopes, up to translation of summands. The summands lie in pairwise orthogonal subspace…

math.CO2026

Imprimitive association schemes and elimination theory

Akihiro Higashitani, Hirotake Kurihara

We prove that a commutative association scheme is imprimitive if and only if it admits a multivariate - or -polynomial structure with respect to an elimination-type monomial…

math.AG2026

Polyptych lattices and marked chain-order polytopes

Naoki Fujita, Akihiro Higashitani

The theory of polyptych lattices is a framework to obtain a family of toric degenerations whose polytopes are related by piecewise-linear transformations. It can be regarded as a g…

math.AC2023

Difference of Hilbert series of homogeneous monoid algebras and their normalizations

Akihiro Higashitani

Let be an affine monoid, the associated monoid -algebra, and its normalization, where we let be a field. In this paper, in the c…

math.AG2023

Newton-Okounkov polytopes of type flag varieties of small ranks arising from cluster structures

Yunhyung Cho, Naoki Fujita, Akihiro Higashitani +1

A flag variety is a smooth projective homogeneous variety. In this paper, we study Newton-Okounkov polytopes of the flag variety arising from its cluster structu…