%0 Journal Article
%T Unitary transformations depending on a small parameter
%A Casas, F.
%A Oteo, J. A.
%A Ros, J.
%J Proceedings of the Royal Society A
%D 2012
%V 468
%N 2139
%I Royal Soc
%@ 1364-5021
%G English
%F Casas_etal2012
%O WOS:000300185400005
%O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=893), last updated on Thu, 01 Mar 2012 10:14:33 +0000
%X We formulate a unitary perturbation theory for quantum mechanics inspired by the Lie-Deprit formulation of canonical transformations. The original Hamiltonian is converted into a solvable one by a transformation obtained through a Magnus expansion. This ensures unitarity at every order in a small parameter. A comparison with the standard perturbation theory is provided. We work out the scheme up to order ten with some simple examples.
%K perturbation theory
%K quantum mechanics
%K unitary transformation
%K Magnus expansion
%R 10.1098/rspa.2011.0388
%U https://doi.org/10.1098/rspa.2011.0388
%P 685-700