B4.2

Representation Theory
Part II, 2003

Assume that the group SL2(F3)S L_{2}\left(\mathbb{F}_{3}\right) of 2×22 \times 2 matrices of determinant 1 with entries from the field F3\mathbb{F}_{3} has presentation

X,P,Q:X3=P4=1,P2=Q2,PQP1=Q1,XPX1=Q,XQX1=PQ\left\langle X, P, Q: X^{3}=P^{4}=1, P^{2}=Q^{2}, P Q P^{-1}=Q^{-1}, X P X^{-1}=Q, X Q X^{-1}=P Q\right\rangle

Show that the subgroup generated by P2P^{2} is central and that the quotient group can be identified with the alternating group A4A_{4}. Assuming further that SL2(F3)S L_{2}\left(\mathbb{F}_{3}\right) has seven conjugacy classes find the character table.

Is it true that every irreducible character is induced up from the character of a 1-dimensional representation of some subgroup?

[Hint: You may find it useful to note that SL2(F3)S L_{2}\left(\mathbb{F}_{3}\right) may be regarded as a subgroup of SU2S U_{2}, providing a faithful 2-dimensional representation; the subgroup generated by PP and QQ is the quaternion group of order 8 , acting irreducibly.]