A Gross-Pitaevskii treatment for supersolid helium.

Understanding the observations of nonlinear rotational susceptibility in samples of solid helium below temperatures of 1 to 200 millikelvin (mK) has been a subject of some controversy. Here, the observations are conjectured to be describable in terms of a rarified Gross-Pitaevskii superfluid of vacancies, with a transition temperature of about 50 mK, whose density is locally enhanced by crystal imperfections. The observations can be greatly affected by this density enhancement. I argue that every pure Bose solid's ground state is a supersolid.