Recent content by liucl78

What is the use of infinite-dimensional representation of lie group? Now, I know Hilbert space is infinite-dimensional, and physical states must be in Hilbert space. However, for massive fields, the transformation group is SO(3), its unitary representation is finite. For massless fields, the...

why massless particle, such as photon, can only have two helicity states? Photon's helicity is 1,-1. Helicity zero is forbidden. why?

You can see a paper. http://arxiv.org/abs/1002.0892 A discussion to contradiction of the number of unknown variables and the number of Maxwell equations