Holomorphic mappings and their fixed points on Spin Factors

Fuente: arXiv
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Autores principales: Mackey, Michael, Mellon, Pauline
Formato: Preprint
Publicado: 2025
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author Mackey, Michael
Mellon, Pauline
author_facet Mackey, Michael
Mellon, Pauline
contents In this paper we study holomorphic properties of infinite dimensional spin factors. Among the infinite dimensional Banach spaces with homogeneous open unit balls, we show that the spin factors are natural outlier spaces in which to ask the question (as was proved in the early 1970s for Hilbert spaces): Do biholomorphic automorphisms $g$ of the open unit ball $B$ have fixed points in $\overline B$? In this paper, for infinite dimensional spin factors, we provide reasonable conditions on $g$ that allow us to explicitly construct fixed points of $g$ lying on $\partial B$. En route, we also prove that every spin factor has the density property. In another direction, we focus on (compact) holomorphic maps $f:B\rightarrow B$, having no fixed point in $B$ and examine the sequence of iterates $(f^n)$. As $(f^n)$ does not generally converge, we instead trace the target set $T(f)$ of $f$, that is, the images of all accumulation points of $(f^n)_n$, for any topology finer than the topology of pointwise convergence on B. We prove for a spin factor that $T(f)$ lies on the boundary of a single bidisc unique to $f$.
format Preprint
id arxiv_https___arxiv_org_abs_2502_00555
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Holomorphic mappings and their fixed points on Spin Factors
Mackey, Michael
Mellon, Pauline
Operator Algebras
Complex Variables
17C69, 32H50, 32M15
In this paper we study holomorphic properties of infinite dimensional spin factors. Among the infinite dimensional Banach spaces with homogeneous open unit balls, we show that the spin factors are natural outlier spaces in which to ask the question (as was proved in the early 1970s for Hilbert spaces): Do biholomorphic automorphisms $g$ of the open unit ball $B$ have fixed points in $\overline B$? In this paper, for infinite dimensional spin factors, we provide reasonable conditions on $g$ that allow us to explicitly construct fixed points of $g$ lying on $\partial B$. En route, we also prove that every spin factor has the density property. In another direction, we focus on (compact) holomorphic maps $f:B\rightarrow B$, having no fixed point in $B$ and examine the sequence of iterates $(f^n)$. As $(f^n)$ does not generally converge, we instead trace the target set $T(f)$ of $f$, that is, the images of all accumulation points of $(f^n)_n$, for any topology finer than the topology of pointwise convergence on B. We prove for a spin factor that $T(f)$ lies on the boundary of a single bidisc unique to $f$.
title Holomorphic mappings and their fixed points on Spin Factors
topic Operator Algebras
Complex Variables
17C69, 32H50, 32M15
url https://arxiv.org/abs/2502.00555