Nonisotropically balanced domains, Lempert function estimates, and the spectral Nevanlinna-Pick problem

الأصل · EN

We introduce the notion of a λ-nonisotropically balanced domain and show that the symmetrized polydisc in Cⁿ, n ≥ 2, is an example of such a domain. Given a λ-nonisotropically balanced domain Ω, we derive effective estimates from above and from below for the Lempert function at (0,z)∈Ω×Ω. We use these estimates to derive certain conditions for realising a two-point Nevanlinna-Pick interpolation in the symmetrized polydisc. Applying the ideas used in the derivation of our Lempert function estimates to the so-called spectral unit ball Ωₙ, we deduce: a) a formula for the Lempert function at (0,W)∈Ωₙ×Ωₙ; and b) a necessary and sufficient condition for realising a two-point Nevanlinna- Pick interpolation in the spectral unit ball.