Approximation by harmonic functions

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For a compact set X ⊂ ℝn we construct a restoring covering for the space h(X) of real-valued functions on X which can be uniformly approximated by harmonic functions. Functions from h(X) restricted to an element Y of this covering possess some analytic properties. In particular, every nonnegative function f ∈ h(Y), equal to 0 on an open non-void set, is equal to 0 on Y. Moreover, when n = 2, the algebra H(Y) of complex-valued functions on Y which can be uniformly approximated by holomorphic functions is analytic. These theorems allow us to prove that if a compact set X ⊂ ℂ has a nontrivial Jensen measure, then X contains a nontrivial compact set Y with analytic algebra H(Y).

Original languageEnglish (US)
Pages (from-to)4415-4427
Number of pages13
JournalTransactions of the American Mathematical Society
Issue number11
StatePublished - 1997


  • Harmonic functions
  • Potential theory
  • Uniform algebras

ASJC Scopus subject areas

  • General Mathematics
  • Applied Mathematics


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