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DTSTART:19700329T010000
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CATEGORIES:Junior Algebra and Number Theory seminar
SUMMARY:Thar she blows - in pursuit of a classification of
finite index subgroups of SL_2(Z) in terms of wal
lpaper groups - Marj Batchelor
DTSTART;TZID=Europe/London:20121019T140000
DTEND;TZID=Europe/London:20121019T150000
UID:TALK41144AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/41144
DESCRIPTION:There is an equivariant map from the upper half pl
ane (with SL_2(Z) acting by mobius transformations
) to the complex plane (with the action of a subgr
oup affine transformations which preserve a triang
ular lattice). The homomorphism from SL_2(Z) onto
this group of affine transformations provides an
obvious source of finite index subgroups of SL_2(Z
). The conjecture is that finite index subgroups a
re all "lifts" of subgroups of the translation sub
group. I will describe why the equivariant map is
plausible\, and talk about the kernel of the homor
phism and the lifts of translation groups.
LOCATION:MR4
CONTACT:Jonathan Nelson
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