Let $\mathcal{B}(F)$ be the algebra of all bounded linear operators on a complex Hilbert space $F$.
Is $T\in \mathcal{B}(F)$ and bijective, is $T$ invertible? i.e. is $T^{-1}\in \mathcal{B}(F)$?
Let $\mathcal{B}(F)$ be the algebra of all bounded linear operators on a complex Hilbert space $F$.
Is $T\in \mathcal{B}(F)$ and bijective, is $T$ invertible? i.e. is $T^{-1}\in \mathcal{B}(F)$?
If $T$ is bijective, then $T^{-1}\in \mathcal{B}(F)$. This is a consequence of the open mapping theorem.