Compactifications of reductive groups as moduli of principal
bundles
-- Michael Thaddeus, October 1, 2010

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Let G be a reductive group over an algebraically closed field
of characteristic zero.  We study a family of moduli problems
where the objects are principal G-bundles on chains of
projective lines, trivialized at the two endpoints.  From
different stability conditions, we get different
compactifications of G as a Deligne-Mumford stack.  In
particular, we extend the notion of "wonderful"
compactification to a semisimple G with nontrivial center, such
as SL(n).  This describes joint work in progress with Johan
Martens.