Behavior of boundary string field theory associated with integrable massless flow

We put forward-an idea that the boundary entropy associated with integrable massless flow of thermodynamic Bethe ansatz (TBA) is identified with tachy on action of boundary string field theory. We show that the temperature par ametrizing a massless flow in the TEA formalism can be identified with tach yon energy for the classical action at least near the ultraviolet fixed poi nt, i.e., the open string vacuum.