- #1
kent davidge
- 933
- 56
Weinberg considers (p.68 QFT Vol. 1) particles with mass M > 0. The Little Group is SO(3). He wants to calculate the rotation
W(Λ,p) ≡ L-1(Λp) Λ L(p). He says that for this we need to choose a standard boost L(p) which carries the four momentum from
kμ = (0,0,0,M) to pμ. He then shows the expressions for the components of L(p). What I don't understand is that because the spatial components of kμ all vanish, i.e. ki = 0, why does it matter to choose a specific set of expressions for (L(p))i j?
W(Λ,p) ≡ L-1(Λp) Λ L(p). He says that for this we need to choose a standard boost L(p) which carries the four momentum from
kμ = (0,0,0,M) to pμ. He then shows the expressions for the components of L(p). What I don't understand is that because the spatial components of kμ all vanish, i.e. ki = 0, why does it matter to choose a specific set of expressions for (L(p))i j?