S - matrix

[Petar Mali]

When I have time dependent Hamiltonian

\hat{H}(t)=\hat{H}_0+\hat{V}(t)

Is then this relation correct?


\psi_S(t)=e^{\frac{1}{i\hbar}\hat{H}_0t}\hat{S}(t) \psi_S(0)

where \hat{S}(t) is S-matrix.


\psi_S(t) - wave function in Schrodinger picture

[Petar Mali]

If I want time dependent density matrix is it

\hat{\rho}_t=e^{\frac{1}{i\hbar}\hat{H}_0t}\hat{S} (t)\hat{\rho}_H\hat{S}^{-1}(t)e^{-\frac{1}{i\hbar}\hat{H}_0t}

Is this expression OK?

So I have


\left\langle \hat{A} \right\rangle_t=Tr(\hat{A}_S\hat{\rho}_t)=\left\la ngle \hat{S}^{-1}(t)\hat{A}_H(t)\hat{S}(t) \right\rangle_{\hat{\rho}_H}

Does it make sense?