Umklapp scattering determines the conductivity of clean metals. In typical quasi one-dimensional Fermi liquids with an open Fermi surface, certain pseudo-momenta do not decay by 2-particle collisions even in situations where Umklapp scattering relaxes the momentum of the quasi particles efficiently. Due to this approximate conservation of pseudo-momentum, a certain fraction of the electrical cu...

We show that the optical spin conductivity being a small AC response of bulk current and elusive in condensed matter systems can be measured ultracold atoms. demonstrate this contains rich information on quantum states by analyzing experimentally achievable such as spin-1/2 superfluid Fermi gas, spin-1 Bose-Einstein condensate, Tomonaga-Luttinger liquid. The obtained spectra absent Drude reflec...