I'm trying to understand fractionalisation, of which spin-charge separation is an example. I've read that this is accomplished by introducing a Lagrange multiplier field, which becomes a dynamical gauge field at low energies.
My question is - does the gauge field emerge because we represent the spin degrees of freedom in terms of slave fermions, which are gauge-invariant, forcing the gauge field upon us? How is this related to the Lagrange multiplier field?
I'm also wondering what forces the gauge field to become dynamical at low energies?
I'd appreciate a good reference where this (or fractionalization and emergent gauge fields) is reviewed.