HYERS-ULAM STABILITY OF A CLOSED OPERATOR IN A HILBERT SPACE
HYERS-ULAM STABILITY OF A CLOSED OPERATOR IN A HILBERT SPACE
We give some necessary and sufficient conditions in order that a closed operator in a Hilbert space into another have the Hyers-Ulam stability. Moreover, we prove the existence of the stability constant for a closed operator. We also determine the stability constant in terms of the lower bound.