Hydrodynamics of Spatially Ordered Superfluids

We derive the hydrodynamic equations for the supersolid and superhexatic phases of a neutral two-dimensional Bose fluid. We find, assuming that the normal part of the fluid is clamped to an underlying substrate, that both phases can sustain third-sound modes and that in the supersolid phase there are additional modes due to the superfluid motion of point defects (vacancies and interstitials).Comment: 24 pages of ReVTeX and 7 uuencoded figures. Submitted for publication in Phys. Rev.

Recent advances in the LTSn method for criticality calculations in slab geometry

The aim of this work is to present a new approach based upon the application of the LTSN method to solve the eigenvalue problem in a slab, namely the problem of criticality. The advances are based on a new iterative method for the solution of the system of equations for the boundary conditions and a new search methodology for the keff based on the bisection method. This method proved to be reliable, specially after the introduction of the restarted generalized minimum residual (RGMRE). We report numerical simulations for keff and critical dimensions determination considering the SN multigroup problem in heterogeneous slab