We continue our analysis of the consequences of the commutation relation $[S,T]=\Id$, where $S$ and $T$ are two closable unbounded operators. The { \em weak} sense of this commutator is given in terms of the inner product of the Hilbert space $\H$ where the operators act. { We also consider what we call, adopting a physical terminology}, a { \em nonlinear} extension of the above commutation relations.
Categories: math-ph math.MP