Nonlinear Realization of Lorentz Symmetry
  We explore a nonlinear realization of the (2+1)-dimensional Lorentz symmetry with a constant vacuum expectation value of the second rank anti-symmetric tensor field. By means of the nonlinear realization, we obtain the low-energy effective action of the Nambu-Goldstone bosons for the spontaneous Lorentz symmetry breaking. 
Naoto Yokoi