Ebert - Psi-k
Ebert - Psi-k
Ebert - Psi-k
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Ludwig<br />
Maximilians-<br />
Universität<br />
München<br />
Spectral representation of G(⃗r, ⃗r ′ , E)<br />
ψ i (⃗r, E i ) complete and orthogonal set of eigenfuctions<br />
(E i − H) ψ i (⃗r, E i ) = 0<br />
(E − H) G(⃗r, ⃗r ′ , E) = δ(⃗r − ⃗r ′ )<br />
G(⃗r, ⃗r ′ , E) for fixed ⃗r ′ and E can be expanded into a<br />
series of ψ i (⃗r, E i ) (Mercer’s theorem)<br />
∑<br />
G + (⃗r, ⃗r ′ , E) = lim<br />
ɛ→0<br />
retarded Green’s function<br />
i<br />
ψ i (⃗r)ψ × i (⃗r ′ )<br />
E − E i + iɛ<br />
poles of G + (⃗r, ⃗r ′ , E) indicate eigenvalues<br />
lim ɛ→0 avoids divergencies<br />
NB: × is in general equivalent to †<br />
KKR07 – p.8/100