Local Variations and Minimal Area Problem for Carathéodory Functions

Roger W. Barnard, Alexander Yu Solynin

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Two kinds of minimal area problems have been studied. One, with analytic side conditions, was first treated by H. S. Shapiro. Another kind of problem initiated by A. W. Goodman deals with classes of analytic univalent functions with geometric constraints. The minimal area problem for the Carathéodory functions, i.e. analytic functions having positive real part in the unit disk, belongs to this second type. To solve it, we develop a technique in the frame of classical complex analysis that explores symmetrization type geometric transformations and local boundary variations. This method reduces the minimal area problem to a certain boundary value problem for analytic functions. In the case that the latter problem admits an explicit solution the original minimal area problem can be handled.

Original languageEnglish
Pages (from-to)135-167
Number of pages33
JournalIndiana University Mathematics Journal
Issue number1
StatePublished - 2004


  • Angular derivative
  • Carathéodory functions
  • Dirichlet integral
  • Local variation
  • Minimal area problem
  • Polarization
  • Symmetrization
  • Univalent function


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