Conformal truncation of chern-simons theory at large N_f

We set up and analyze the lightcone Hamiltonian for an abelian Chern-Simons field coupled to N_f fermions in the limit of large N_f using conformal truncation, i.e. with a truncated space of states corresponding to primary operators with dimension below a maximum cutoff Δ_max. In both the Chern-Simons theory, and in the O(N) model at infinite N, we compute the current spectral functions analytically as a function of Δ_max and reproduce previous results in the limit that the truncation Δ_max is taken to ∞. Along the way, we determine how to preserve gauge invariance and how to choose an optimal discrete basis for the momenta of states in the truncation space.