First Order Galilean Superfluid Dynamics

We study dynamics of (anomalous) Galilean superfluid up to first order in derivative expansion, both in parity-even and parity-odd sectors. We construct a relativistic system -- null superfluid, which is a null fluid (introduced in [arXiv:1509.04718]) with a spontaneously broken global $U(1)$ symmetry. A null superfluid is in one to one correspondence with Galilean superfluid in one lower dimension, i.e. they have same symmetries, thermodynamics, constitutive relations and are related to each other by a mere choice of basis. The correspondence is based on null reduction, which is known to reduce the Poincar\'{e} symmetry of a theory to Galilean symmetry in one lower dimension. To perform this analysis, we use offshell formalism of (super)fluid dynamics, adopting it appropriately to null (super)fluids.