TY - JOUR

T1 - Perturbation theory and Padé approximants in realistic large-matrix models of the nuclear effective interaction

AU - Hofmann, H. M.

AU - Starkand, Y.

AU - Kirson, M. W.

PY - 1976/8/2

Y1 - 1976/8/2

N2 - Realistic extended shell-model calculations are used to construct exact effective Hamiltonians, the perturbation series for the effective Hamiltonian to any order, and the [N+1, N] Padé approximants to the series. It is found that the Padé approximants give reliable results even when the series diverge, but that for both convergent and divergent series reasonably accurate results can be obtained only in fifth, or even seventh order. In addition, the poles of the low-order Padé approximants are not always reliable indicators of singularities of the perturbation series. The perturbation series and Padé approximants for the Q-box (energy-dependent effective Hamiltonian) are no more accurate in low orders than those for the usual effective Hamiltonian. Explicit formulas for the matrix Padé approximants are given in an appendix.

AB - Realistic extended shell-model calculations are used to construct exact effective Hamiltonians, the perturbation series for the effective Hamiltonian to any order, and the [N+1, N] Padé approximants to the series. It is found that the Padé approximants give reliable results even when the series diverge, but that for both convergent and divergent series reasonably accurate results can be obtained only in fifth, or even seventh order. In addition, the poles of the low-order Padé approximants are not always reliable indicators of singularities of the perturbation series. The perturbation series and Padé approximants for the Q-box (energy-dependent effective Hamiltonian) are no more accurate in low orders than those for the usual effective Hamiltonian. Explicit formulas for the matrix Padé approximants are given in an appendix.

UR - http://www.scopus.com/inward/record.url?scp=49549136609&partnerID=8YFLogxK

U2 - 10.1016/0375-9474(76)90287-6

DO - 10.1016/0375-9474(76)90287-6

M3 - Article

AN - SCOPUS:49549136609

SN - 0375-9474

VL - 266

SP - 138

EP - 162

JO - Nuclear Physics, Section A

JF - Nuclear Physics, Section A

IS - 1

ER -