id: 06057714
dt: j
an: 06057714
au: Xu, Ye-Jun; Wang, Chang-Chun; Wang, Xian-Cai; Fan, Hong-Yi
ti: Generalized Hellmann-Feynman theorem for ensemble average expressed in the
    formalism of pure state expectation.
so: Int. J. Theor. Phys. 51, No. 4, 1062-1068 (2012).
py: 2012
pu: Springer, New York, NY
la: EN
cc: 
ut: generalized Hellmann-Feynman theorem; thermal vacuum state; von Neumann
    entropy
ci: 
li: doi:10.1007/s10773-011-0981-x
ab: Summary: We show that the generalized Hellmann-Feynman theorem (GHFT) for
    ensemble average can be expressed in the formalism of pure state
    expectation. We employ the thermo field dynamics proposed by Umezawa
    and Takahash to realize this goal, the pure state $|0(β)\rangle $ is
    defined in doubled eigenvector space of the Hamiltonian. Relation
    between the GHFT and entropy-variation in the context of $|0(β)\rangle
    $ is also derived.
rv: