Hokkaido University Preprint Series in Mathematics
The spectrum a(T¢) of a Toeplitz operator Tt/> on the open unit disc n for a unimodular symbol <Pis studied. Exactly, many sufficient conditions for a(T¢) . an or a(T¢) = lJ are given. If <Pis a unimodular function in H00 + C, then a(T¢) an or a(T¢ ) = D.