@Article{Casas_etal2012,
author="Casas, F.
and Oteo, J. A.
and Ros, J.",
title="Unitary transformations depending on a small parameter",
journal="Proceedings of the Royal Society A",
year="2012",
publisher="Royal Soc",
volume="468",
number="2139",
pages="685--700",
optkeywords="perturbation theory; quantum mechanics; unitary transformation; Magnus expansion",
abstract="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.",
optnote="WOS:000300185400005",
optnote="exported from refbase (https://references.ific.uv.es/refbase/show.php?record=893), last updated on Thu, 01 Mar 2012 10:14:33 +0000",
issn="1364-5021",
doi="10.1098/rspa.2011.0388",
opturl="https://doi.org/10.1098/rspa.2011.0388",
language="English"
}