  The recently proposed fermion bag approach is a powerful technique to solve
some four-fermion lattice field theories. Due to the existence of a duality
between strong and weak couplings, the approach leads to efficient Monte Carlo
algorithms in both these limits. The new method allows us for the first time to
accurately compute quantities close to the quantum critical point in the three
dimensional lattice Thirring model with massless fermions on large lattices.
The critical exponents at the quantum critical point are found to be
$\nu=0.85(1)$, $\eta = 0.65(1)$ and $\eta_\psi = 0.37(1)$.
