Renormalization-Group Analysis of Bicritical and Tetracritical Points

摘要: Recently developed renormalization-group techniques are summarized and exploited to yield a analysis of bicritical tetracritical points (which arise in antiferromagnets boson systems). For $n\ensuremath{\lesssim}3$ an isotropic or Heisenberg fixed point dominates gives behavior; but for $n\ensuremath{\gtrsim}4$ new "biconical" with irrational $\ensuremath{\epsilon}$-expansion coefficients appears. This describes may be relevant displacive phase transitions.