Cluster variational method for hyperonic nuclear matter with coupled channels

The cluster variational method for infinite nuclear matter is reformulated in a second quantization approach to take into account ΛN-ΣN coupled channel in the hyperon-nucleon interaction. The two-body central potential including ΛN-ΣN coupling is adopted for the even-state hyperon-nucleon interaction, and we investigate this even-state coupling effect on the energy of uniform baryon matter composed of neutron, Λ, and Σ⁰ hyperons. For the odd-state hyperon-nucleon interaction we adopted the single-channel central potential, whereas the Argonne v18 two-nucleon potential and the Urbana IX three-nucleon potential are employed as the interactions between nucleons. Using those bare baryon interactions including ΛN-ΣN coupling, we calculate the expectation value of the Hamiltonian with the extended Jastrow wave function in the two-body cluster approximation. By comparing the obtained energies with and without ΛN-ΣN coupled channel, it is found that the ΛN-ΣN central coupling effect on the energy of baryon matter is relatively small. (author)