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We study integrable cases of pairing BCS hamiltonians containing several types of fermions. We prove that there exist three classes of such integrable models associated with classical rational r -matrices and Lie algebras gl(2m), sp(2m) and so(2m) correspondingly. We diagonalize the constructed hamiltonians by means of the algebraic Bethe ansatz. In the partial case of two types of fermions (m=2) the obtained models may be interpreted as N=Z proton–neutron integrable models. In particular, in the case of sp(4) we recover the famous integrable proton–neutron model of Richardson. 相似文献