Critical behavior of the (2+1)-dimensional Thirring model

We investigate chiral symmetry breaking in the ( 2 + 1)-dimensional Thirring model as a function of the coupling as well as the Dirac flavor number N-f with the aid of the functional renormalization group. For small enough flavor number N-f < N-f(cr), the model exhibits a chiral quantum phase transition for sufficiently large coupling. We compute the critical exponents of this second order transition as well as the fermionic and bosonic mass spectrum inside the broken phase within a next-to-leading order derivative expansion. We also determine the quantum critical behavior of the many-flavor transition which arises due to a competition between vector and chiral-scalar channels and which is of second order as well. Due to the problem of competing channels, our results rely crucially on the RG technique of dynamical bosonization. For the critical flavor number, we find N-f(cr) similar or equal to 5.1 with an estimated systematic error of approximately one flavor.