# Representation of SU(2)xU(1)

1. Jul 15, 2013

### lalo_u

Well, i´m trying to understand this:

I´ve got a representation of $SU(2)_L\otimes U(1)_Y$ such that the left lepton doublets can be represented as (2, -1) and lepton singlets rights as (1, -2).

Then I can be left antiparticles bilinear representations as $(2,1)\times(2,1)$ or $(1,-2)\times(1,-2)$.

I wonder why, in the first case the possibilities are $(1,2)+(3,2)$, and in the second case is $(1,-4)$.

What kind of math operation has been done here?