SINGULARITIES NEAR-CRITICAL AND BICRITICAL END-POINTS - APPLICATIONS TO AN ISOMORPHOUS TRANSITION

We study a system that has an isomorphous transition using an eighth-o rder Landau-type free energy function. The phase diagram of such syste m has a critical line that meets a first-order phase boundary at a cri tical end point. This phase boundary is also limited by two other crit ical lines that meet at a bicritical end point. We showed that this ph ase boundary close to the end point exhibits a nonanalytic behavior as sociated with the singularities of the critical line, confirming simil ar result we previously obtained using scaling arguments. Related univ ersal amplitude ratios are then computed. Next, the critical lines nea r the bicritical end point are also analyzed and checked for singulari ties.