摘要
In the conformally covariant classical field theory, the energy-momemtum tensors for the massless spin 0, 1, 1/2 and 2 fields are traceless (Butut, A. O. & Xu, B. W., J.Phys., A15 L207; Xu, B. W., ibid., A14 L97; 15 L329; Birrell, N. D. & Davies, P.C. W., Quantum Fields in Curved Space, p. 174). On the other hand, it is well
