In this paper, a new transformation is introduced to solve triple sine-Gordon equation. It is shown that this intermediate transformation method is powerful to
A variational approach is developed to study the groundstate (GS) of the two-site Holstein model. By the extended coherent state, where the more phonon correlat
Using the recursion method, we study the phase transitions of the Ashkin-Teller model on the Bethe lattice,restricting ourselves to the case of ferromagnetic in