We analyze this free energy functional as follows: (i) For T < T 0 , we have a local maximum at η η = 0 , and since the free energy is bounded below, there must be two local minima at nonzero values η η − − ( T ) < 0 and η η + ( T ) > 0 . The cubic term ensures that η η + is the global minimum since it is deeper. (ii) For T just above T 0 , the minimum at η η − − disappears, the maximum at η η = 0 turns into a local minimum, but the minimum at η η + persists and continues to be the global minimum. As the temperature is further raised, F ( T , η η + ( T ) ) rises until it equals zero at some temperature T ∗ ∗ . At T ∗ ∗ we get a discontinuous jump in the global minimum from η η + ( T ∗ ∗ ) to 0. (The minima cannot coalesce for that would require the first three derivatives of F to vanish at η η = 0 .)