Mixed neutron-star-plus-wormhole systems: Equilibrium configurations
  We study gravitationally bound, spherically symmetric equilibrium configurations consisting of ordinary (neutron-star) matter and of a phantom/ghost scalar field which provides the nontrivial topology in the system. For such mixed configurations, we show the existence of static, regular, asymptotically flat general relativistic solutions. Based on the energy approach, we discuss the stability as a function of the core density of the neutron matter for various sizes of the wormhole throat. 
Vladimir Dzhunushaliev, Vladimir Folomeev, Burkhard Kleihaus, Jutta   Kunz
gr-qc astro-ph.SR