The interaction between hyperons and the surface gravitational redshift of proto neutron star PSR J0740+6620

. An effect of the contributions from σ ∗ and φ mesons on the surface gravitational redshift of PNS PSR J0740+6620 is studied with relativistic mean field theory in consideration of a baryon octet. We find that the energy density ε increases relative to the same pressure p as the contributions from σ ∗ and φ mesons are taken into account. Relative to the same central energy density, the radius R of the PNS increases while the mass M , the mass radius ratio M/R and the surface gravitational redshift z of the PNS decrease, taking into account the contributions from σ ∗ and φ mesons. Under the constraint of mass M =2.08 M (cid:12) , considering the contributions from σ ∗ and φ mesons, for the PNS PSR J0740+6620, the radius decreases by about -0.08%, the central energy density increases by about 0.89%, the central pressure increased by about 0.76%, the mass radius ratio increases by about 0.08%, and the surface gravitational redshift increases by about 0.17% from z =0.31663 to z =0.31718.