# A Mathematical Physics Question

• Mathematica
Let be the propagators for the Schroedinguer,Klein-Gordon and Dirac?...are they hermitian operators?..are their eigenfunctions ortogonal?...

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Hi! This is my first post.
Do you mean "propagators are Unitary"? I think a propagator is an operator which governs time evolution of an eigenstate. In order that total of probability obtained from the integration of the eigenstate's inner product remains 1 in the course of time evolution, time evolution operator should be Unitary. If so, I think propagators are Green's function used to solve a problem by perturbation method. So although a time evolution operator of an exact solution of the problem should be Unitary, propagators are not neccesarily Unitary, I think. Propagators are not the operators which should be diagonalized by eigenfunctions in order to solve the problem. I heard that S matrix which is constructed by a propagator is Unitary, though. How do you think about this.

jeff