3.II.19F

Representation Theory
Part II, 2006

(a) Let G=SU2G=\mathrm{SU}_{2}, and let VnV_{n} be the space of homogeneous polynomials of degree nn in the variables xx and yy. Thus dimVn=n+1\operatorname{dim} V_{n}=n+1. Define the action of GG on VnV_{n} and show that VnV_{n} is an irreducible representation of GG.

(b) Decompose V3V3V_{3} \otimes V_{3} into irreducible representations. Decompose 2V3\wedge^{2} V_{3} and S2V3\mathrm{S}^{2} V_{3} into irreducible representations.

(c) Given any representation VV of a group GG, define the dual representation VV^{*}. Show that VnV_{n}^{*} is isomorphic to VnV_{n} as a representation of SU2\mathrm{SU}_{2}.

[You may use any results from the lectures provided that you state them clearly.]