Generators, Relations and Symmetries in Pairs of 3x3 Unimodular Matrices

Denote the free group on two letters by F2 and the SL(3,C)-representation variety of F2 by R = Hom(F2, SL(3,C)). There is a SL(3,C)-action on the coordinate ring of R, and the geometric points of the subring of invariants is an affine variety X. We determine explicit minimal generators and defining relations for the subring of invariants and show X is a degree 6 hyper-surface in C9 mapping onto C8. Our choice of generators exhibit Out(F2) symmetries which allow for a succinct expression of the defining relations.Comment: 21 pages. This fourth version is the author's final version which includes new comments and some correction

E-polynomial of the SL(3,C)-character variety of free groups

We compute the E-polynomial of the character variety of representations of a rank r free group in SL(3, C). Expanding upon existing techniques, we stratify the space of representations and compute the E-polynomial of each geometrically described stratum using fibrations. Consequently, we also determine the E-polynomial of its smooth, singular, and abelian loci and the corresponding Euler characteristic in each case. Along the way, we give new proofs of the SL(2,C), PGL(2,C), and PGL(3,C) cases.Comment: 21 pages; accepted for publication at the Pacific Journal of Mathematic

Spin networks and SL(2,C)-Character varieties

Denote the free group on 2 letters by F_2 and the SL(2,C)-representation variety of F_2 by R=Hom(F_2,SL(2,C)). The group SL(2,C) acts on R by conjugation. We construct an isomorphism between the coordinate ring C[SL(2,C)] and the ring of matrix coefficients, providing an additive basis of C[R]^SL(2,C) in terms of spin networks. Using a graphical calculus, we determine the symmetries and multiplicative structure of this basis. This gives a canonical description of the regular functions on the SL(2,C)-character variety of F_2 and a new proof of a classical result of Fricke, Klein, and Vogt.Comment: Updated historical treatment of the subject. Figures drawn with PGF/TikZ; Handbook of Teichmuller Theory II, A. Papadopoulos (ed), EMS Publishing House, Zurich, 200

Fundamental Groups of Character Varieties: Surfaces and Tori

We compute the fundamental group of moduli spaces of Lie group valued representations of surface and torus groups.Comment: v2: 12 pages, minor edits, accepted for publication at Mathematische Zeitschrif