TY - JOUR
T1 - An improvement on a theorem of Ben Martin
AU - Neeman, Amnon
PY - 2000
Y1 - 2000
N2 - Let π be the fundamental group of a Riemann surface of genus g ≥ 2. The group π has a well-known presentation, as the quotient of a free group on generators {a1, a2, . . . , ag, b1, b2, . . . , bg} by the one relation [a1, b1][a2, b2] ⋯ [ag, bg] = 1. This gives two inclusions F π, where F is the free group on g generators; we could map the generators to the a's, or to the b's. Call the images of these inclusions F1 ⊂ π and F2 ⊂ π. Given a connected, reductive group G over an algebraically closed field of characteristic 0, any representation π → G restricts to two representations f1 : F1 → G, f2 : F2 → G. We prove that on a Zariski open, dense subset of the space of pairs of representations {f1, f2}, there exists a representation f : π → G lifting them, up to (separate) conjugacy of f1 and f2. Ben Martin proved this theorem, with the hypothesis that the semisimple rank of G is > g. We remove the hypothesis.
AB - Let π be the fundamental group of a Riemann surface of genus g ≥ 2. The group π has a well-known presentation, as the quotient of a free group on generators {a1, a2, . . . , ag, b1, b2, . . . , bg} by the one relation [a1, b1][a2, b2] ⋯ [ag, bg] = 1. This gives two inclusions F π, where F is the free group on g generators; we could map the generators to the a's, or to the b's. Call the images of these inclusions F1 ⊂ π and F2 ⊂ π. Given a connected, reductive group G over an algebraically closed field of characteristic 0, any representation π → G restricts to two representations f1 : F1 → G, f2 : F2 → G. We prove that on a Zariski open, dense subset of the space of pairs of representations {f1, f2}, there exists a representation f : π → G lifting them, up to (separate) conjugacy of f1 and f2. Ben Martin proved this theorem, with the hypothesis that the semisimple rank of G is > g. We remove the hypothesis.
UR - http://www.scopus.com/inward/record.url?scp=0034348901&partnerID=8YFLogxK
U2 - 10.4310/MRL.2000.v7.n4.a7
DO - 10.4310/MRL.2000.v7.n4.a7
M3 - Article
SN - 1073-2780
VL - 7
SP - 411
EP - 415
JO - Mathematical Research Letters
JF - Mathematical Research Letters
IS - 4
ER -