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Perturbation Theory with a Non‐Complete Set of Hamiltonian Eigenstates
Author(s) -
Potapkov N. A.
Publication year - 1974
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220620116
Subject(s) - eigenvalues and eigenvectors , hamiltonian (control theory) , anisotropy , perturbation (astronomy) , mathematics , physics , mathematical physics , quantum mechanics , mathematical analysis , mathematical optimization
A method is proposed of constructing a perturbation theory in which a non‐complete set of eigenstates of the non‐perturbated Hamiltonian is used. The expansion of the expectation value of the energy and magnetization of an anisotropic ferromagnet at T = 0 in powers of I a / I is obtained. In this expansion the zero order, the first, and the second‐order terms are completely taken into account.