The Lattice NJL Model at Non-zero Baryon and Isospin Densities

We present initial results of a numerical investigation of the chiral symmetry restoring transition in the (3+1)-dimensional Nambu – Jona-Lasinio model with both non-zero baryon chemical potential ( μ B ≠ 0 ) and isospin chemical potential ( μ I ≠ 0 ). With non-zero isospin chemical potential, the model suffers from a sign problem. We proceed in two ways: (i) We perform “partially quenched” simulations in which μI is made non-zero only during the measurement of chiral observables; (ii) We perform full simulations with imaginary isospin chemical potential with the aim to analytically continue results to real μI.