Gauge transformations and anharmonic effects in smectic liquid crystals

We explore the effects of including anharmonic terms in the gauge-transformed smectic-A Hamiltonian. We recover the results of Grinstein and Pelcovits concerning the nonhydrodynamic behavior of the elastic constants, and show that the anharmonic terms do not destroy the long-range order in the superconducting gauge. © 1982 The American Physical Society.