The U(1) Topological Gauge Field Theory for Topological Defects in   Liquid Crystals
  A novel U(1) topological gauge field theory for topological defects in liquid crystals is constructed by considering the U(1) gauge field is invariant under the director inversion. Via the U(1) gauge potential decomposition theory and the $\phi$-mapping topological current theory, the decomposition expression of U(1) gauge field and the unified topological current for monopoles and strings in liquid crystals are obtained. It is revealed that monopoles and strings are located in different spatial dimensions and their topological charges are just the winding numbers of $\phi$-mapping. 
Yi-shi Duan, Li Zhao, Xin-hui Zhang and Tie-yan Si