5 papers
Magnitude and motivic zeta functions of matroids
Junnosuke Koizumi
We prove that the magnitude of the tope graph of a simple oriented matroid is the specialization at of the motivic zeta function of its underlying matroid. This refines the…
Magnitude homology of tope graphs
Junnosuke Koizumi
We completely determine the magnitude homology of tope graphs of real hyperplane arrangements. Their ranks can be described as the Hilbert functions of the Stanley--Reisner rings o…
Magnitude homology of real hyperplane arrangements
Junnosuke Koizumi, Ye Liu
We define and study the magnitude and magnitude homology of a real hyperplane arrangement by regarding its tope graph as a metric space. We prove several structural results for the…
Irrationality of the reciprocal sum of doubly exponential sequences
Junnosuke Koizumi
We show that sequences of positive integers whose ratios lie within a specific range are almost uniquely determined by their reciprocal sums. For instance, the Sylv…
On iterated circumcenter sequences
Shuho Kanda, Junnosuke Koizumi
An iterated circumcenter sequence (ICS) in dimension is a sequence of points in where each point is the circumcenter of the preceding points. The purpose o…