Comment on ‘‘Optimal auxiliary Hamiltonians for truncated boson-space calculations by means of a maximal-decoupling variational principle’’

The general applicability of a recently proposed method that utilizes optimal auxiliary Hamiltonians in a truncated ideal boson space is discussed. The description of excited states by this method is considered in particular. In a model test calculation a comparison is made to another procedure that utilizes energy-independent effective operators. The latter procedure seems to be superior for the description of excited states. We briefly comment on further prospects for both methods.