Strange stars: Can their crust reach the neutron drip density?

Abstract

Electrostatic potential of electrons near the surface of static strange stars at zero temperature is studied within the frame of the MIT bag model. We find that for QCD parameters within rather wide ranges, and if the nuclear crust on the strange star is at a density leading to neutron drip, the electrostatic potential is insufficient to establish an outwardly directed electric field, which is crucial for the survival of such crusts. If a minimum gap width of 200 fm is called in for a more stringent constraint, our calculations completely rule out the possibility of such crusts' presence on strange stars. Therefore, our results prefer against the existence of neutron-drip crust in nature.