Roles of isoscalar hyperons in probing the density dependence of the nuclear symmetry energy

The role of the isoscalar hyperon Λ in probing the density dependence of the nuclear symmetry energy is studied in multi-Λ hypernuclei, hyperon-rich matter and neutron stars in relativistic models. Relationships between the properties of three types of objects and the neutron thickness in 208Pb are established with respect to the isoscalar–isovector coupling that modifies the density dependence of the symmetry energy. The exotic isotopes far from the neutron drip line can be stabilized by filling in considerable Λ hyperons. The difference of the binding energy of multi-Λ hypernuclei from different models is attributed to different symmetry energies. The isovector potential together with the neutron thickness in multi-Λ hypernuclei investigated is very sensitive to the isoscalar–isovector coupling. The large sensitivity of the Λ hyperon fraction to the isoscalar–isovector coupling occurs at about 2–3ρ0 in beta equilibrated hyperon-rich matter. In neutron stars with hyperonization, an on–off effect with respect to the isoscalar–isovector coupling exists for the neutron star radius.