Gallone, MatteoMichelangeli, Alessandro2021-02-222021-02-222020https://openscience.sissa.it/handle/1963/35422We produce a simple criterion and a constructive recipe to identify those self-adjoint extensions of a lower semi-bounded symmetric operator on Hilbert space which have the same lower bound as the Friedrichs extension. Applications of this abstract result to a few instructive examples are then discussedenSelf-adjoint extensions ·Lower semi-bounded symmetric operatorsFriedrichs extensionsArticle