Anisotropy lifts the degeneracy of your higher band so there are two effective-masses. The higher band gets to be the large-hole band and the light hole band. The anisotropy splits the degeneracy even in a cubic-lattice crystal. Inversion symmetry refers to your program that has the identical Houses as http://manuelvrdyc.collectblogs.com/41636743/about-birefringent-effects