Sumito Hasegawa

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20182026

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math.AG2026

The rationality problem for multinorm one tori, II

Sumito Hasegawa, Kazuki Kanai, Yasuhiro Oki

We investigate the stable and retract rationality of multinorm one tori associated to finite {é}tale algebras. Our results are organized according to the greatest common divisor $d…

math.AG2025

The rationality problem for multinorm one tori

Sumito Hasegawa, Kazuki Kanai, Yasuhiro Oki

In this paper, we study the rationality problem for multinorm one tori, a natural generalization of norm one tori. For multinorm one tori that split over finite Galois extensions w…

math.AG2018

Rationality problem for norm one tori in small dimensions

Sumito Hasegawa, Akinari Hoshi, Aiichi Yamasaki

We classify stably/retract rational norm one tori in dimension $n - 1$ for $n = 2^{e}$ $(e \geq 1)$ is a power of $2$ and $n = 12, 14, 15$ . Retract non-rationality of norm one tori for prim…