Conjecture on biholomorphic Loewner chains in reflexive Banach spaces

Let XX be a reflexive complex Banach space with unit ball B\mathbb{B}, let AL(X)A\in L(X), and write k+(A)k_+(A) and m(A)m(A) for the quantities used in the source. An AA-normalized univalent subordination chain f(z,t)f(z,t) is obtained as the limit

limtetAv(z,s,t)=f(z,s).\lim_{t\to\infty}e^{tA}v(z,s,t)=f(z,s).

Here vv is the solution of the associated initial value problem, and a standard solution satisfies the Loewner PDE outside a null set of times.

Biholomorphic-chain conjecture. If k+(A)<2m(A)k_+(A)<2m(A) and f(z,t)f(z,t) is the AA-normalized univalent subordination chain given by the displayed limit, then f(,t)f(\cdot,t) is biholomorphic on B\mathbb{B} for every t0t\geq 0, and f(z,t)f(z,t) is a standard solution of

ft(z,t)=Df(z,t)h(z,t).\frac{\partial f}{\partial t}(z,t)=Df(z,t)h(z,t).

The conjecture concerns the extension of finite-dimensional Loewner PDE results to infinite-dimensional reflexive Banach spaces. The source notes that it is true when X=CnX=\mathbb{C}^n, while the general infinite-dimensional case remains open.

Sources & referencesView supporting material

Primary source

Ian Graham, Hidetaka Hamada, Gabriela Kohr and Mirela Kohr, “Loewner PDE in infinite dimensions”, arXiv:2309.13263 (2023).

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