Tricritical three-phase line
= Tricritical three-phase line
{title2=$h=0,\quad r=3u^2/(16v),\quad u<0$}
For $V=rm^2/2+um^4/4+vm^6/6-hm$ with $v>0$, the displayed line has three <global minima>, $m=0$ and $m=\pm\sqrt{-3u/(4v)}$. The factorization $V=(v/6)m^2(m^2+3u/(4v))^2$ proves their coexistence. Two nonzero-field <tricritical wings> and the zero-field ordered coexistence sheet meet along this line. Its order-parameter discontinuity tends to zero as it terminates at the <tricritical point>.