Iteration of holomorphic maps in Hilbert spaces

Previous work (Gong-ning Chen, J. Math. Anal. Appl.98 (1984), 305–313) on iteration of holomorphic maps of Cⁿ is continued. The purpose of this note is to extend results given in the above mentioned reference to the case of complex Hilbert spaces. Other comments are appended.     

Harmonic maps between complex projective spaces

Using the DoCarmo-Wallach theory, we classify (homogeneous) polynomial harmonic maps of complex projective spaces into spheres and complex projective spaces in terms of finite dimensional moduli spaces. We make use of representation theory of the (special) unitary group to give, for a spherical range, the exact dimension and, for complex projective spaces, a lower bound of the dimension of the moduli spaces.Supported in part by NSF Grant DMS 8603172.Research done in part while the third named author was on leave at University of California, Berkeley.     

Union of linear spaces in infinite-dimensional projective spaces and holomorphic vector bundles

Let V be a localizing Banach space with an unconditional countable basis, X an equicodimensional transversal union of finite-codimensional linear subspaces of P(V) and E a holomorphic vector bundle of finite rank on X. Here we prove that Hⁱ(X,E) = 0 for every i > 0 and that E is isomorphic to a direct sum of line bundles ^OX(t).     

Note on equivariant harmonic maps in complex projective spaces

We give a simple criterion for equivariant harmonic maps into complex projective spaces CP ⁿ . As an application of the criterion, we give examples of equivariant harmonic cylinders. We also give examples of non-equivariant harmonic cylinders as perturbations of equivariant harmonic cylinders.     

Deformation of holomorphic maps onto the blow-up of the projective plane

Let S be the blow-up of the projective plane at d distinct points and be any surjective holomorphic map from a compact complex manifold S^′. We will show that all deformations of ψ come from automorphisms of S if d?3. The result is optimal in the sense that it is not true if d?2. The strategy of the proof is to use the infinitesimal automorphisms of the web geometry on S arising from the natural foliations of S induced by the pencils of the lines through the blow-up centers.     

Random iterations of holomorphic maps in complex Banach spaces

Conditions guaranteeing the uniform convergence to constant maps of random iterations of holomorphic contractions on unbounded domains in complex Banach spaces are established.

     

Stochastics and thermodynamics for equilibrium measures of holomorphic endomorphisms on complex projective spaces

It was proved by Urbański and Zdunik (Fund Math 220:23–69, 2013) that for every holomorphic endomorphism $f:{{\mathbb { P}}}^k\rightarrow {{\mathbb { P}}}^k$ of a complex projective space ${{\mathbb { P}}}^k,k\ge 1$ , there exists a positive number $\kappa _f>0$ such that if $J$ is the Julia set of $f$ (i.e. the support of the maximal entropy measure) and $\phi :J\rightarrow {\mathbb R}$ is a Hölder continuous function with $\sup (\phi )-\inf (\phi )<\kappa _f$ (pressure gap), then $\phi $ admits a unique equilibrium state $\mu _\phi $ on $J$ . In this paper we prove that the dynamical system ( $f,\mu _\phi $ ) enjoys exponential decay of correlations of Hölder continuous observables as well as the Central Limit Theorem and the Law of Iterated Logarithm for the class of these variables that, in addition, satisfy a natural co-boundary condition. We also show that the topological pressure function $t\mapsto P(t\phi )$ is real-analytic throughout the open set of all parameters $t$ for which the potentials $t\phi $ have pressure gaps.     

Hyperbolic imbedding and spaces of continuous extensions of holomorphic maps

LetX be a complex subspace of a complex spaceY. We show that hyperbolic imbeddedness ofX inY is characterized by relative compactness in the compact-open topology of certain spaces of continuous extensions of holomorphic maps from the punctured diskD* toX and fromM -A toX whereM is a complex manifold andA is a divisor onM with normal crossings. We apply these characterizations to obtain generalizations and extensions of theorems of Kobayashi, Kiernan, Kwack, Noguchi and Vitali forD and for higher dimensions. Relative compactness ofX inY is not assumed.     

On non-isotropic harmonic maps of surfaces into complex projective spaces

It is proved by purely algebraic method that weakly conformai, conformai andA _z ³ = 0 are mutually equivalent if ϕ :Ω→ℂP ⁿ is a non-isotropic harmonic map and the harmonic maps with isotropy order ≥3 are uniquely determined by a system of ordinary differential equations. A method is given, by which the isotropy orders of non-isotropic harmonic maps can be computed.     

An extension theorem for holomorphic functions of slow growth on covering spaces of projective manifolds

LetX be a projective manifold of dimension n ≥ 2 andY →X an infinite covering space. EmbedX into projective space by sections of a sufficiently ample line bundle. We prove that any holomorphic function of sufficiently slow growth on the preimage of a transverse intersection ofX by a linear subspace of codimension <n extends toY. The proof uses a Hausdorff duality theorem for L₂ cohomology. We also show that every projective manifold has a finite branched covering whose universal covering space is Stein.     

Universaln-soft maps ofn-dimensional spaces in absolute Borel and projective classes

LetC be one of the absolute Borel classesM _α ,A _α , with 1≤α<ω ₁ or one of the absolute projective classesP _k ,k≥1. A map of ann-dimensional spaceX ∈ C onto the Hilbert cube which is ann-soft map in Shchepin's sense and universal in the class of maps of spaces of dimension smaller that or equal ton from the classC into separable metrizable spaces is constructed. Translated fromMatematicheskie Zametki, Vol. 60, No. 6, pp. 845–850, December, 1996.