Abstract

We study numerical computation of conformal invariants of domains in the complex plane. In particular, we provide an algorithm for computing the conformal capacity of a condenser. The algorithm applies to a wide variety of geometries: domains are assumed to have smooth or piecewise smooth boundaries. The method we use is based on the boundary integral equation method developed and implemented in [1]. A characteristic feature of this method is that, with small changes in the code, a wide spectrum of problems can be treated. We compare the performance and accuracy to previous results in the cases when numerical data is available and also in the case of several model problems where exact results are available.

Highlights

  • During the past fifty years conformal invariants have become crucial tools for complex analysis

  • We review the application of the integral equation to compute the conformal mapping from doubly connected domains onto an annulus {z : q < |z| < 1}, q ∈ (0, 1), and present the MATLAB implementation of the method

  • If ρ is the unique solution of the boundary integral equation (9) and the piecewise constant function h is given by (10), the function f with the boundary values (11) is analytic in the domain G with f (∞) = 0, the conformal mapping Φ is given by z − z2 z − z1 ef (z), z ∈ G ∪ Γ, (16)

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Summary

Introduction

During the past fifty years conformal invariants have become crucial tools for complex analysis. In cases for which the analytic formulas are unknown, the computational performance may be analysed by observing convergence features of the results under successive refinements of the numerical model, and error estimates maybe based on general theory. In those relatively few cases we have found in the literature where the analytic formula is known, the true error estimate may be given.

Conformal mapping onto annulus
Numerical solution of the integral equation
Computing the conformal mapping for bounded domains
Computing the conformal mapping for unbounded domains
Computing the capacity of the doubly connected domain G
Two confocal ellipses
Complete elliptic integrals
Jacobi’s inversion formula for μ
Square in square
Polygon in polygon
Complement of two slits
Two segments on the real axis
Two vertical segments
Two general segments
Rings with a segment as a boundary component
Segment and circle
Segment and ellipse
Segment and polygon
The upper half-plane with a slit
Two rectangles
A vertical rectangle in the upper half-plane
The hyperbolic capacity and the elliptic capacity
The hyperbolic capacity
The elliptic capacity
A disk
A square
Amoeba-shaped boundary
Concluding Remarks
Full Text
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