In the recent paper (Pulé J V and Zagrebnov V A 2004 The approximating Hamiltonian method for the imperfect boson gas J. Phys. A: Math. Gen. 45 3565–83 ) the pressure for the imperfect (mean field) boson gas is derived by a method based on the approximating Hamiltonian argument. We give some comments about this derivation.
In two recent papers (Baranger et al 2001 J. Phys. A: Math. Gen. 34 7227; 2002 J. Phys. A: Math. Gen. 35 9493) co-authored by us, we mentioned the work of Dr Kenneth G Kay (Kay 1994 J. Chem. Phys. 100(6) 4377; 100 4432) in an unfavourable light. In this comment we correct this impression, as it was based on a misunderstanding of his work. The point at issue has been the derivation of the Herman–Kluk formula (Herman and Kluk 1984 Chem. Phys. 91 27). We find Kay's derivation to be the most solid at the moment.