PT Journal
AU Blanes, S
   Casas, F
   Oteo, JA
   Ros, J
TI A pedagogical approach to the Magnus expansion
SO European Journal of Physics
JI Eur. J. Phys.
PY 2010
BP 907
EP 918
VL 31
IS 4
DI 10.1088/0143-0807/31/4/020
LA English
AB Time-dependent perturbation theory as a tool to compute approximate solutions of the Schrodinger equation does not preserve unitarity. Here we present, in a simple way, how the Magnus expansion (also known as exponential perturbation theory) provides such unitary approximate solutions. The purpose is to illustrate the importance and consequences of such a property. We suggest that the Magnus expansion may be introduced to students in advanced courses of quantum mechanics.
ER