  On the basis of first-principle Monte Carlo simulations we find that the
screw dislocation along the hexagonal axis of an hcp He4 crystal features a
superfluid core. This is the first example of a regular quasi-one-dimensional
supersolid, and one of the cleanest cases of a regular Luttinger-liquid system.
In contrast, the same type of screw dislocation in solid Hydrogen is
insulating.
