Equations of state for bicritical points. III. Cubic anisotropy and tetracriticality

Crossover scaling functions for a two-component spin system with quadratic anisotropy g and cubic anisotropy ̃ \~v are calculated to first order in ε=4-d and in ̃ \~v, near the transitions within the ordered phases below the multicritical point (T=Tₘ,g=0). Emphasis is placed on the mechanism by which the system is driven to bicritical or tetracritical behavior by the dangerous irrelevant variable ̃ \~v. Explicit expressions and graphs for the various thermodynamic scaling functions are presented.