C INVART    SOURCE    CHAT      05/01/13    00:42:27     5004           

      SUBROUTINE INVARI_T (SIG,N,T)
      IMPLICIT INTEGER(I-N)
      integer n
      real*8 sig(n),t,J2,J3
      t=0.D0
      call Invari_J2(sig,n,J2)
      if (J2.gt.0.D0) then
         call Invari_J3(sig,n,J3)
         t=3.D0*dsqrt(3.D0)*J3/(2.D0*J2**1.5D0)
         if (t.lt.-1.D0) t=-1.D0
         if (t.gt.1.D0)  t=1.D0
         t=acos(t)/3.D0
      endif
      return
      end