Influence of the weakly interacting light U boson on the properties of massive protoneutron stars

Considering the octet baryons in relativistic mean field theory and selecting entropy per baryon S=1, we calculate and discuss the influence of U bosons on the equation of state, mass-radius, moment of inertia and gravitational redshift of massive protoneutron stars (PNSs). The effective coupling constant g_U of U bosons and nucleons is selected from 0 to 70 GeV^-2. The results indicate that U bosons will stiffen the equation of state (EOS). The influence of U bosons on the pressure is more obvious at low density than high density, while the influence of U bosons on the energy density is more obvious at high density than low density. The U bosons play a significant role in increasing the maximum mass and radius of PNS. When the value of g_U changes from 0 to 70 GeV^-2, the maximum mass of a massive PNS increases from 2.11M_⊙ to 2.58M_⊙, and the radius of a PNS corresponding to PSR J0348+0432 increases from 13.71 km to 24.35 km. The U bosons will increase the moment of inertia and decrease the gravitational redshift of a PNS. For the PNS of the massive PSR J0348+0432, the radius and moment of inertia vary directly with g_U, and the gravitational redshift varies approximately inversely with g_U.