The effect of inclusion of $\Delta$ resonances in relativistic   mean-field model with scaled hadron masses and coupling constants
  Knowledge of the equation of state of the baryon matter plays a decisive role in the description of neutron stars. With an increase of the baryon density the filling of Fermi seas of hyperons and $\Delta$ isobars becomes possible. Their inclusion into standard relativistic mean-field models results in a strong softening of the equation of state and a lowering of the maximum neutron star mass below the measured values. We extend a relativistic mean-field model with scaled hadron masses and coupling constants developed in our previous works and take into account now not only hyperons but also the $\Delta$ isobars. We analyze available empirical information to put constraints on coupling constants of $\Delta$s to mesonic mean fields. We show that the resulting equation of state satisfies majority of presently known experimental constraints. 
K. A. Maslov, E. E. Kolomeitsev, D. N. Voskresensky
nucl-th astro-ph.HE hep-ph