Hamiltonians of a wide-spread class of
Ginv-invariant nonlinear quantum models, including multiboson and frequency conversion ones, are expressed as non-linear functions of
sl(2) generators. It enables us to use standard variational schemes, based on
sl(2) generalized coherent states as trial functions, for solving both spectral and evolution tasks. In such a manner a new analytical expression is found for energy spectra in a mean-field approximation which is beyond quasi-equidistant ones obtained earlier.
Hamiltonians of a wide-spread class of strongly coupled quantum system models are expressed as nonlinear functions of
sl(2) generators. It enables us to use the
sl(2) formalism, in particular,
sl(2) generalized coherent states (GCS) for solving both spectral and evolution tasks. In such a manner, using standard variational schemes with
sl(2) GCS as trial functions we find new analytical expressions for energy spectra and non-linear evolution equations for cluster dynamics variables in mean-field approximations which are beyond quasi-harmonic ones obtained earlier. General results are illustrated on certain concrete models of quantum optics and laser physics.
The model of nonlinear disturbed mechanism for one-dimensional Fermi gas is investigated. Firstly, the corresponding functional is constructed; secondly, its Lagrange operator is selected; using the modified generalized variational iteration method, the approximate analytic solutions of corresponding path curves are obtained. A simple example is given, and the approximation accuracy obtained by using the modified generalized variational iteration method is shown to be better. The aim of this article is to provide a valid method of solving the nonlinear physical problems.