Paper 1, Section II, F

Representation Theory
Part II, 2010

(i) Let NN be a normal subgroup of the finite group GG. Without giving detailed proofs, define the process of lifting characters from G/NG / N to GG. State also the orthogonality relations for GG.

(ii) Let a,ba, b be the following two permutations in S12S_{12},

and let G=a,bG=\langle a, b\rangle, a subgroup of S12S_{12}. Prove that GG is a group of order 12 and list the conjugacy classes of GG. By identifying a normal subgroup of GG of index 4 and lifting irreducible characters, calculate all the linear characters of GG. Calculate the complete character table of GG. By considering 6 th roots of unity, find explicit matrix representations affording the non-linear characters of GG.