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Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions

100%

Girela D.

Colloquium Mathematicum

1996

tom 69

nr 1

19-17

A well known result of Beurling asserts that if f is a function which is analytic in the unit disc $Δ ={z ∈ ℂ : |z|<1} $ and if either f is univalent or f has a finite Dirichlet integral then the set of points $e^{iθ}$ for which the radial variation $V(f,e^{iθ})=∫_{0}^{1}|f'(re^{iθ})|dr$ is infinite is a set of logarithmic capacity zero. In this paper we prove that this result is sharp in a very strong sense. Also, we prove that if f is as above then the set of points $e^{iθ}$ such that $(1 - r)|f'(re^{iθ})| ≠ o(1)$ as r → 1 is a set of logarithmic capacity zero. In particular, our results give an answer to a question raised by T. H. MacGregor in 1983.

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The generalized Neumann-Poincaré operator and its spectrum

40%

Partyka D.

Instytut Matematyczny Polskiej Akademii Nauk

CONTENTS Introduction..........................................................................................................................................................................5 Preliminaries. Complex harmonic functions..........................................................................................................................7 I. Spectral values and eigenvalues of a Jordan curve........................................................................................................19 1.1. On a boundary integral..............................................................................................................................................20 1.2. The generalized Cauchy singular integral operator $C_𝕍$.......................................................................................23 1.3. The Hilbert transformation $T_Ω$.............................................................................................................................28 1.4. The boundary space Ḣ²(∂Ω)......................................................................................................................................31 1.5. The generalized Neumann-Poincaré operator $N_𝕍$...............................................................................................36 II. Quasisymmetric automorphisms of the unit circle...........................................................................................................41 2.1. The Douady-Earle extension $E_γ$..........................................................................................................................42 2.2. On an approximation of the Hersch-Pfluger distortion function $Φ_K$......................................................................46 2.3. On the maximal dilatation of the Douady-Earle extension..........................................................................................48 2.4. The Hilbert space H...................................................................................................................................................54 2.5. The linear operator $B_γ$.........................................................................................................................................60 III. The generalized harmonic conjugation operator............................................................................................................64 3.1. The generalized harmonic conjugation operator $A_γ$.............................................................................................64 3.2. Spectral values and eigenvalues of a quasisymmetric automorphism of the unit circle..............................................73 3.3. The smallest positive eigenvalue of a quasisymmetric automorphism of the unit circle..............................................80 3.4. Limiting properties of spectral values and eigenvalues of a quasisymmetric automorphism of the unit circle............84 IV. Spectral values of a quasicircle.....................................................................................................................................90 4.1. Characterizations of the boundary space Ḣ²(∂Ω).......................................................................................................91 4.2. Spaces symmetric with respect to a Jordan curve.....................................................................................................93 4.3. Plemelj's formula for a quasicircle..............................................................................................................................96 4.4. The main spectral theorem for quasicircles.............................................................................................................103 4.5. Spectral values and eigenvalues of a quasicircle....................................................................................................108 Appendix. The inner completion of pseudo-normed spaces............................................................................................114 References......................................................................................................................................................................117 List of symbols.................................................................................................................................................................122 Index................................................................................................................................................................................124

Ograniczanie wyników

1 Colloquium Mathematicum

1 Girela D.

1 Partyka D.

1 1997

1 1996

Wyniki wyszukiwania

Radial growth and variation of univalent functions and of Dirichlet finite holomorphic functions

The generalized Neumann-Poincaré operator and its spectrum