We prove that the image of
the mapping class group by the representations arising in the SU(2)-TQFT is
infinite, provided that the genus g ≥ 2 and the level of the theory r≠2,3,4,6 (and
r≠10 for g = 2). In particular it follows that the quotient groups ℳg∕N(tr) by
the normalizer of the r-th power of a Dehn twist t are infinite if g ≥ 3 and
r≠2,3,4,6,8,12.
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