3 papers
math.CV2025
Indefinite structure of the Bergman kernel on the open unit disk
Kenta Kojin, Shuhei Kuwahara, Michio Seto
In this paper, we focus on an indefinite structure lying behind the Bergman kernel on the open unit disk. In particular, an invariant distance, birational maps and an indefinite ke…
math.FA2025
Isometric Gelfand transforms of complete Nevanlinna-Pick spaces
Kenta Kojin
We show that any complete Nevanlinna-Pick space whose multiplier algebra has isometric Gelfand transform (or commutative C*-envelope) is essentially the Hardy space on the open uni…
math.FA2021
A refined nc Oka-Weil theorem
Kenta Kojin
This short note refines nc Oka-Weil theorem by using a characterization of free compact nc sets based on the notion of dilation hulls. A consequence of it is that any free holomorp…