Franz Schwabl Quantum Mechanics 4th Edit · Problem 6.2

Motion in an Electromagnetic Field

Physics — Quantum Mechanics · associated-laguerre-polynomials

Problem

Show that for the associated Laguerre polynomials Lrs(x)=(d/dx)sLr(x),L^s_r(x) = (d/dx)^s L_r(x) \quad, Lr(x)=ex(d/dx)re−xxr,L_r(x) = e^x (d/dx)^r e^{-x} x^r \quad, the following relations hold: (a) Lrs(x)=∑k=0r−s(−1)k+s[r!]2xkk! (k+s)! (r−k−s)!\displaystyle L^s_r(x) = \sum_{k=0}^{r-s} (-1)^{k+s} \frac{[r!]^2 x^k}{k!\,(k+s)!\,(r-k-s)!}, (b) (−1)me−xt/(1−t)(1−t)m+1=∑n=0∞tr(r+m)!Lr+mm(x)\displaystyle \frac{(-1)^m e^{-xt/(1-t)}}{(1-t)^{m+1}} = \sum_{n=0}^{\infty} \frac{t^r}{(r+m)!} L^m_{r+m}(x).

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