Universal Correlations as Fingerprints of Transverse Quantum Fluids*

We study universal off-diagonal correlations in transverse quantum fluids, which are a new class of quasi-one-dimensional superfluids featuring long-range-ordered ground states.  The concept of transverse quantum fluids originally emerged in the context of superfluid edge dislocations in ⁴He but it was recently realized that there exists a broad class of quasi-one-dimesional superfluids featuring similar properties. Transverse quantum fluids come in two types: the ones with a parabolic dispersion, and the incoherent ones with diffusive behavior. Both types  exhibit unique self-similar space-time scaling relations in the variable x²/Dτ that serve as fingerprints of the specific states.  The results obtained with the effective field theory are found to be in perfect agreement with ab initio simulations of hard-core bosons on a lattice. This allows an accurate determination, at nonzero temperature and finite system size, of such key ground-state properties as the condensate and superfluid densities, as well as the transverse quantum fluid specific parameter D.