Bogomolnyi-type bounds in unconventional superconductors without external magnetic fields

Following Bogomolnyi's classical treatment of vortices, we develop a method for finding rigorous lower bounds to the Landau-Ginzburg free energy describing unconventional superconductors in the absence of external magnetic fields. This allows a more precise description of the magnetic instabilities previously considered in these systems. In particular, we derive new sufficient conditions for the stability of both the homogeneous and inhomogeneous equilibrium states.