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arXiv · 2406.09234

Determination of the distance from a projection to nilpotents

Masaki Izumi·Michiya Mori
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Abstract

In this note, we study the distance from an arbitrary nonzero projection $P$ to the set of nilpotents in a factor $\mathcal{M}$ equipped with a normal faithful tracial state $\tau$. We prove that the distance equals $(2\cos \frac{\tau(P)\pi}{1+2\tau(P)})^{-1}$. This is new even in the case where $\mathcal{M}$ is the matrix algebra. The special case settles a conjecture posed by Z. Cramer.

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Masaki Izumi, Michiya Mori. 2024-06-13. Determination of the distance from a projection to nilpotents. https://arxiv.org/abs/2406.09234

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