Compact operators and Toeplitz algebras on multiply-connected domains

If Ω is a smoothly bounded multiply-connected domain in the complex plane and S belongs to the Toeplitz algebra τ of the Bergman space ofΩ, we show that S is compact if and only if its Berezin transform vanishes at the boundary of Ω. We also show that every element S in T, the C ∗-subalgebra of τ generated by Toeplitz operators with symbols in H ∞ (Ω), has a canonical decomposition S = T S + R for some R in the commutator ideal CT; and S is in CT iff the Berezin transform S vanishes identically on the set M1 of trivial Gleason parts. © 2011 Elsevier Inc. All rights reserved