Relativistic Mean-Field Models with Scaled Hadron Masses and Couplings: Hyperons and Maximum Neutron Star Mass

摘要

An equation of state of cold nuclear matter with an arbitrary isotopiccomposition is studied within a relativistic mean-field approach with hadronmasses and coupling constants depending self-consistently on the scalarmean-field. All hadron masses decrease universally with the scalar fieldgrowth, whereas meson-nucleon coupling constants can vary differently. Morespecifically we focus on two modifications of the KVOR model studiedpreviously. One extension of the model (KVORcut) demonstrates that the equationof state stiffens if the increase of the scalar-field magnitude with thedensity is bounded from above at some value for baryon densities above thesaturation nuclear density. This can be realized if the nucleon vector-mesoncoupling constant changes rapidly as a function of the scalar field slightlyabove the desired value. The other version of the model (MKVOR) utilizes asmaller value of the nucleon effective mass at the nuclear saturation densityand a saturation of the scalar field in the isospin asymmetric matter inducedby a strong variation of the nucleon isovector-meson coupling constant asfunction of the scalar field. A possibility of hyperonization of the matter inneutron star interiors is incorporated. Our equations of state fulfill majorityof known empirical constraints including the pressure-density constraint fromheavy-ion collisions, direct Urca constraint, gravitational-baryon massconstraint for the pulsar J0737-3039B, and the constraint on the maximum massof the neutron stars.