Uniform rational approximation algebra with prescribed poles
ID: uniform-rational-approximation-algebra-with-prescribed-poles
Let be compact and permit polynomial terms and finite poles in , meeting every bounded complementary component. In the uniform closure of these rational functions, the coordinate has spectrum exactly . Indeed the set of with is relatively open by invertibility and relatively closed by uniform continuity of the scalar resolvent; it meets each component by a prescribed pole, or by a Neumann expansion at infinity. It is therefore all of . Holomorphic functional calculus then places every function holomorphic near in , proving prescribed-pole Runge approximation theorem.
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