A new approach to $γ$-bounded representations

Fuente: arXiv
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Autor principal: Merdy, Christian Le
Formato: Preprint
Publicado: 2024
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author Merdy, Christian Le
author_facet Merdy, Christian Le
contents Let $X$ be a Banach space, let $(Ω,μ)$ be a $σ$-finite measure space and let $A,B\colonΩ\to B(X)$ be strongly measurable $γ$-bounded functions. We show that for all $x\in X$ and all $x^*\in X^*$, there exist a Hilbert space $K$ and two measurable functions $a_1\in L^\infty(Ω;K)$ and $a_2\in L^\infty(Ω;K)$ such that $\langle B(t)A(s)x,x^*\rangle = (a_2(t)\,\vert\, a_1(s))_{K}$ for a.e. $(s,t)$ in $Ω^2$, with $\Vert a_1\Vert_\infty \Vert a_2\Vert_\infty\leq γ(A)γ(B)\Vert x\vert\vert x^*\Vert$. This factorization property allows us to improve or simplify some results concerning $γ$-bounded representations of groups or semigroups.
format Preprint
id arxiv_https___arxiv_org_abs_2402_10736
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A new approach to $γ$-bounded representations
Merdy, Christian Le
Functional Analysis
47A99, 22D12, 47D06, 47A60
Let $X$ be a Banach space, let $(Ω,μ)$ be a $σ$-finite measure space and let $A,B\colonΩ\to B(X)$ be strongly measurable $γ$-bounded functions. We show that for all $x\in X$ and all $x^*\in X^*$, there exist a Hilbert space $K$ and two measurable functions $a_1\in L^\infty(Ω;K)$ and $a_2\in L^\infty(Ω;K)$ such that $\langle B(t)A(s)x,x^*\rangle = (a_2(t)\,\vert\, a_1(s))_{K}$ for a.e. $(s,t)$ in $Ω^2$, with $\Vert a_1\Vert_\infty \Vert a_2\Vert_\infty\leq γ(A)γ(B)\Vert x\vert\vert x^*\Vert$. This factorization property allows us to improve or simplify some results concerning $γ$-bounded representations of groups or semigroups.
title A new approach to $γ$-bounded representations
topic Functional Analysis
47A99, 22D12, 47D06, 47A60
url https://arxiv.org/abs/2402.10736