Multicritical behavior of disordered systems with two order parameters

A field-theoretic description of phase transitions in disordered systems with two coupled order parameters is given. An analysis of renormalization-group functions is performed directly for three-dimensional systems in a two-loop approximation by using the Pade-Borel summation technique. Fixed points are found corresponding to stable multicritical behavior. The effect of frozen point impurities on the phase diagrams of the system is studied.