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We characterize two classical types of conformality of a holomorphic self-map of the unit disk at a boundary point - existence of a finite angular derivative in the sense of Carath\'eodory and the weaker property of angle preservation - in…

Complex Variables · Mathematics 2024-10-21 Pavel Gumenyuk , Maria Kourou , Annika Moucha , Oliver Roth

On a closed and connected symplectic manifold, the group of Hamiltonian diffeomorphisms has the structure of an infinite-dimensional Fr\'echet Lie group, where the Lie algebra is naturally identified with the space of smooth and zero-mean…

Symplectic Geometry · Mathematics 2024-12-19 Lev Buhovsky , Maksim Stokić

For various Hilbert spaces of analytic functions on the unit disk, we characterize when a function $f$ has optimal polynomial approximants given by truncations of a single power series. We also introduce a generalized notion of optimal…

Functional Analysis · Mathematics 2023-07-11 Christopher Felder

We prove an automatic convergence theorem for holomorphic modular forms on tube domains. The argument works in some generality, and covers in particular the case of orthogonal groups, symplectic groups, unitary and quaternion unitary…

Number Theory · Mathematics 2026-03-03 Aaron Pollack

Assume that two algebraic varieties of finite type over the complex numbers are related by a morphism whose fibers are precisely the orbits for the action of a unipotent group. We show that the two varieties have the same topological Euler…

Algebraic Geometry · Mathematics 2021-04-02 Mario Maican

In this paper we analyse the structure of the spaces of smooth type functions, generated by elements of arbitrary Hilbert spaces, as a continuation of the research in our previous papers in this series. We prove that these spaces are…

Functional Analysis · Mathematics 2018-12-05 Aparajita Dasgupta , Michael Ruzhansky

Let $\mathcal F$ be a holomorphic foliation on a compact K\'ahler surface with hyperbolic singularities and no foliation cycle. We prove that if the limit set of $\mathcal F$ has zero Lebesgue measure, then its complement is a modification…

Complex Variables · Mathematics 2022-02-03 Bertrand Deroin , Christophe Dupont , Victor Kleptsyn

Let $(\phi_t)$ be a holomorphic semigroup of the unit disc (i.e., the flow of a semicomplete holomorphic vector field) without fixed points in the unit disc and let $\Omega$ be the starlike at infinity domain image of the Koenigs function…

Complex Variables · Mathematics 2018-10-19 Filippo Bracci , Manuel D. Contreras , Santiago Díaz-Madrigal , Hervé Gaussier , Andrew Zimmer

In this note, we consider meromorphic univalent functions $f(z)$ in the unit disc with a simple pole at $z=p\in(0,1)$ which have a $k$-quasiconformal extension to the extended complex plane $\hat{\mathbb C},$ where $0\leq k < 1$. We denote…

Complex Variables · Mathematics 2015-02-19 Bappaditya Bhowmik , Goutam Satpati , Toshiyuki Sugawa

Let $\{U_t \}_{t \in {\mathbb D}}$ be a family of topological disks on the Riemann sphere containing the origin 0 whose boundaries undergo a holomorphic motion over the unit disk $\mathbb D$. We study the question of when there exists a…

Dynamical Systems · Mathematics 2023-09-06 Saeed Zakeri

The convergence of DP Fourier series which are neither strongly convergent nor strongly divergent is discussed in terms of the Taylor series of the corresponding inner analytic functions. These are the cases in which the maximum disk of…

Complex Variables · Mathematics 2015-05-05 Jorge L. deLyra

We prove a boundary version of the open mapping theorem for holomorphic maps between strongly pseudoconvex domains. That is, we prove that the local image of a holomorphic map $f:D\to D'$ close to a boundary regular contact point $p\in \de…

Complex Variables · Mathematics 2012-11-27 Filippo Bracci , John Erik Fornaess

In this paper we establish a gap theorem for the complex geometry of smoothly bounded convex domains which informally says that if the complex geometry near the boundary is close to the complex geometry of the unit ball, then the domain…

Complex Variables · Mathematics 2017-06-23 Andrew Zimmer

Ordinary theta-functions can be considered as holomorphic sections of line bundles over tori. We show that one can define generalized theta-functions as holomorphic elements of projective modules over noncommutative tori (theta-vectors).…

Quantum Algebra · Mathematics 2007-05-23 Albert Schwarz

Let $\Omega\subset\mathbb R^2$ be a chord arc domain. We give a simple proof of the the following fact, which is commonly known to be true: a nontrivial harmonic function which vanishes continuously on a relatively open set of the boundary…

Analysis of PDEs · Mathematics 2026-04-20 Stefano Vita

Let $X$ be a compact metric space. By $2^X$ we denote the hyperspace of all closed and non-empty subsets of $X$ endowed with the Hausdorff metric. Let $f:X\to X$ be a continuous function. In this paper we study some topological properties…

General Topology · Mathematics 2025-02-06 Jorge M. Martínez-Montejano , Héctor Méndez , Yajaida N. Velázquez-Inzunza

Extending well-known results on surfaces, we give bounds on the cohomological action of automorphisms of compact K\"ahler threefolds. More precisely, if the action is virtually unipotent we prove that the norm of $(f^n)^*$ grows at most as…

Algebraic Geometry · Mathematics 2019-03-08 Federico Lo Bianco

We discuss a general result of holomorphic extension of a real analytic function $f$ defined on the boundary $\partial D$ of a real analytic strictly convex subset $D\subset\subset \C^n$. We show that this follows from the hypothesis of…

Complex Variables · Mathematics 2009-11-10 L. Baracco

It is known that there exist functions in certain de Branges--Rovnyak spaces whose Taylor series diverge in norm, even though polynomials are dense in the space. This is often proved by showing that the sequence of Taylor partial sums is…

Complex Variables · Mathematics 2023-05-11 Pierre-Olivier Parisé , Thomas Ransford

We characterize functions of $d$-tuples of bounded operators on a Hilbert space that are uniformly approximable by free polynomials on balanced open sets.

Functional Analysis · Mathematics 2015-09-04 Jim Agler , John E. McCarthy