Influence of Striction Effects on the Multicritical Behavior of   Homogeneous Systems
  A field-theoretical description of the behavior of homogeneous, elastically isotropic, compressible systems characterized by two order parameters at the bicritical and tetracritical points is presented. For three-dimensional Ising-like systems, a similar description is performed in the two-loop approximation in three dimensions. The renormalization group equations are analyzed, and fixed points corresponding to different types of multicritical behavior are determined. It is shown that the effect of elastic strains causes a change from a bicritical behavior to a tetracritical one and leads to the appearance of a wide variety of multicritical points. 
S.V. Belim