Symmetry Nonrestoration in the Pati-Salam Model

We demonstrate that symmetry need not be restored in the Pati-Salam model, so that $SU(2)_L\otimes SU(2)_R\otimes SU(4)_c$ remains broken to the Standard Model group at temperatures above the Pati-Salam symmetry breaking scale. Including the leading finite-temperature corrections, suitable quartic couplings prevent a restoration transition, thereby avoiding the thermal production of 't Hooft-Polyakov monopoles after inflation, even if the reheating temperature is very high. This removes monopole-based constraints on the Pati-Salam symmetry breaking scale.