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Let U be the closed unit disc in C and let p be a point on the unit circle. Let f be a continuous function on U which extends holomorphically from each circle contained in U and centered at the origin, and from each circle contained in U…

Complex Variables · Mathematics 2009-06-09 Josip Globevnik

Consider a continuous one parameter family of circles in complex plane that contains two circles lying in the exterior of one another. Under mild assumptions on the family, we prove that if a continuous function on the union of the above…

Complex Variables · Mathematics 2007-05-23 A. Tumanov

Under very general conditions it is shown that if $A$ is a uniform algebra generated by real-analytic functions, then either $A$ consists of all continuous functions or else there exists a disc on which every function in $A$ is holomorphic.…

Complex Variables · Mathematics 2017-10-10 Alexander J. Izzo

Let M be a simply-connected complete Kahler manifold whose sectional curvature is bounded between two negative numbers. In this paper we prove the existence of non-constant bounded holomorphic functions on M if the complex dimension of M is…

Complex Variables · Mathematics 2016-02-09 Jianguo Cao , Mei-Chi Shaw

Recently, Charpentier showed that there exist holomorphic functions $f$ in the unit disk such that, for any proper compact subset $K$ of the unit circle, any continuous function $\phi$ on $K$ and any compact subset $L$ of the unit disk,…

Complex Variables · Mathematics 2021-06-09 Konstantinos Maronikolakis

We introduce a class of regular continuous functions on the closed 2-disk and show that each function from this class is topologically conjugate to a linear function defined on a sqare, a closed half-disk or a closed disk.

General Topology · Mathematics 2009-10-16 Yevgen Polulyakh

The initial motivation for this paper is to discuss a more concrete approach to an approximation theorem of Axler and Shields, which says that the uniform algebra on the closed unit disc closure(D) generated by z and h --- where h is a…

Complex Variables · Mathematics 2010-12-09 Gautam Bharali , Sushil Gorai

Using results from theory of operators on a Hilbert space, we prove approximation results for matrix-valued holomorphic functions on the unit disc and the unit bidisc. The essential tools are the theory of unitary dilation of a contraction…

Complex Variables · Mathematics 2023-06-27 Daniel Alpay , Tirthankar Bhattacharyya , Abhay Jindal , Poornendu Kumar

We prove that there is a continuous non-negative function $g$ on the unit sphere in $\cd$, $d \geq 2$, whose logarithm is integrable with respect to Lebesgue measure, and which vanishes at only one point, but such that no non-zero bounded…

Complex Variables · Mathematics 2009-09-25 B. Korenblum , J. McCarthy

It is a classical theorem that if a function is integrable along the boundary of the unit circle, then the function is the nontangential limit of a holomorphic function on the open disc if and only if its Fourier coefficients for…

Complex Variables · Mathematics 2022-12-20 William E. Gryc

The classical Hadamard three circle theorem is generalized to complete K\"ahler manifolds. More precisely, we show that the nonnegativity of the holomorphic sectional curvature is a necessary and sufficient condition for the three circle…

Differential Geometry · Mathematics 2014-09-09 Gang Liu

It is shown that quasi all continuous functions on the unit circle have the property that, for many small subsets E of the circle, the partial sums of their Fourier series considered as functions restricted to E exhibit certain universality…

Classical Analysis and ODEs · Mathematics 2015-05-20 Juergen Mueller

It was recently established that a function which is harmonic on an infinite cylinder and vanishes on the boundary necessarily extends to an entire harmonic function. This paper considers harmonic functions on an annular cylinder which…

Classical Analysis and ODEs · Mathematics 2017-05-26 Stephen J. Gardiner , Hermann Render

Let be F a family of curves in the unit disc. We show that the set of all functions f holomorphic on the unit disc, which satisfy the following condition, is G-delta and dense in the space of all functions holomorphic on the unit disc: For…

Complex Variables · Mathematics 2007-05-23 Daniel Mayenberger

The paper gives the following characterization of the disc algebra in terms of the argument principle: A continuous function f on the unit circle T extends holomorphically through the unit disc if and only if for each polynomial P such that…

Complex Variables · Mathematics 2007-05-23 Josip Globevnik

We consider holomorphic functions on the unit disc whose images are contained in a strip of the complex plane. Under an additional condition, such functions are constants. We also consider appropriate operator valued versions. Applications…

Functional Analysis · Mathematics 2024-06-12 Tirthankar Bhattacharyya , Anthony G. O'Farrell , Shubham Rastogi , Vijaya Kumar U

Let $D$ be the open unit disc in the complex plane. We denote by $\mathbb{C}$ the set of complex numbers and consider any compact set $K$ which is disjoint from $D$ and which also has connected complement. Let $A(K)$ denote all the…

Complex Variables · Mathematics 2015-06-05 Nikos Tsirivas

In this paper we study a continuity of the "values" of modular functions at the real quadratic numbers which are defined in terms of their cycle integrals along the associated closed geodesics. Our main theorem reveals a more finer…

Number Theory · Mathematics 2019-11-12 Yuya Murakami

Let B be the open unit ball in C^2 and let a, b, c be three points in C^2 which do not lie in a complex line, such that the complex line through a and b meets B and such that <a|b> is different from 1 if one of the points a, b is in B and…

Complex Variables · Mathematics 2011-01-19 Josip Globevnik

A Herglotz function is a holomorphic map from the open complex unit disk into the closed complex right halfplane. A classical Herglotz function has an integral representation against a positive measure on the unit circle. We prove a free…

Operator Algebras · Mathematics 2020-05-26 J. E. Pascoe , Benjamin Passer , Ryan Tully-Doyle
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