inner product spaces, Cauchy-Schwarz’s inequality, reverse inequality, error estimate, 46C05, 26D15, O177.1, A
Weighted shifts, near subnormal operators, subnormal operators, hyponormal operators, the M-P generalized inverse, 47B37, 47B20, O177.1
Hilbert space, hyponormal operators, weighted shifts, spectrum, 47A10, 47B20