- #1
PRB147
- 127
- 0
The O(N) nonlinear sigma model has topological solitons only when N=3 in the
planar geometry. There exists a generalization of the O(3) sigma model so that the
new model possesses topological solitons for arbitrary N in the planar geometry. It is
the CP^{N-1} sigma model,whose group manifold is
[tex]CP^{N-1}= U(N)/[U(1)\bigotimes U(N-1)] =SU(N)/[U(1)\bigotimes SU(N)\bigotimes SU(N-1)][/tex]
The homotopy theorem tells
[tex] \pi_2(CP^{N-1})=Z [/tex]
since [tex]\pi_2(G/H) =\pi_1(H) [/tex] (when G is simply connected) and [tex]\pi_n(G\bigotimes G')=\pi_n (G)\bigoplus \pi_n(G') [/tex] . It is also called the SU(N) sigma model.
Would anyone gives a more detailed hints to the following sentences:
[tex]CP^{N-1}= U(N)/[U(1)\bigotimes U(N-1)] =SU(N)/[U(1)\bigotimes SU(N)\bigotimes SU(N-1)][/tex]
The homotopy theorem tells
[tex] \pi_2(CP^{N-1})=Z [/tex]
since [tex]\pi_2(G/H) =\pi_1(H) [/tex] (when G is simply connected) and [tex]\pi_n(G\bigotimes G')=\pi_n (G)\bigoplus \pi_n(G') [/tex]
U(N) seems to be not simply connected.
planar geometry. There exists a generalization of the O(3) sigma model so that the
new model possesses topological solitons for arbitrary N in the planar geometry. It is
the CP^{N-1} sigma model,whose group manifold is
[tex]CP^{N-1}= U(N)/[U(1)\bigotimes U(N-1)] =SU(N)/[U(1)\bigotimes SU(N)\bigotimes SU(N-1)][/tex]
The homotopy theorem tells
[tex] \pi_2(CP^{N-1})=Z [/tex]
since [tex]\pi_2(G/H) =\pi_1(H) [/tex] (when G is simply connected) and [tex]\pi_n(G\bigotimes G')=\pi_n (G)\bigoplus \pi_n(G') [/tex] . It is also called the SU(N) sigma model.
Would anyone gives a more detailed hints to the following sentences:
[tex]CP^{N-1}= U(N)/[U(1)\bigotimes U(N-1)] =SU(N)/[U(1)\bigotimes SU(N)\bigotimes SU(N-1)][/tex]
The homotopy theorem tells
[tex] \pi_2(CP^{N-1})=Z [/tex]
since [tex]\pi_2(G/H) =\pi_1(H) [/tex] (when G is simply connected) and [tex]\pi_n(G\bigotimes G')=\pi_n (G)\bigoplus \pi_n(G') [/tex]
U(N) seems to be not simply connected.