  We study low-energy effective field theories for non-Fermi liquids with Fermi
surfaces of general dimensions and co-dimensions. When the dimension of Fermi
surface is greater than one, low-energy particle-hole excitations remain
strongly coupled with each other across the entire Fermi surface. In this case,
even the observables that are local in the momentum space (such as the Green's
functions) become dependent on the size of the Fermi surface in singular ways,
resulting in an ultraviolet/infrared (UV/IR) mixing. By tuning the dimension
and co-dimension of the Fermi surface independently, we find perturbative
non-Fermi liquid fixed points controlled by both UV/IR mixing and interactions.
