The Quarterly Journal of Mathematics Advance Access published online on July 11, 2009
The Quarterly Journal of Mathematics, doi:10.1093/qmath/hap022
SINGULAR DRESSING ACTIONS ON HARMONIC MAPS


Departamento de Matemática, Universidade da Beira Interior, Rua Marquês dÁvila e Bolama 6201-001 Covilhã, Portugal
Corresponding author. E-mail: rpacheco{at}mat.ubi.pt
Received 23 February 2009;
revised 27 May 2009
| Abstract |
|---|
In this paper we prove that any harmonic map
from a two-sphere S2 into an arbitrary compact semisimple matrix Lie group G may be reduced to a constant by using the singular dressing actions introduced in (M. J. Bergvelt and M. A. Guest, Action of loop groups on harmonic maps, Trans. Amer. Math. Soc. 326 (1991), 861–886); this reduction induces a factorization of
into flag factors S2
G, and the singular dressing actions are produced from curves of simple factors (rational loops having a minimum number of singularities, whose dressing action can be computed explicitly) for G
. A version of this result for an arbitrary inner symmetric space G/K is established. We also prove generating theorems for the rational loops of the fundamental representations of Sp (n)
and SU (n)
: in both cases the class of generators is slightly larger than the class of simple factors.
E-mail: ncorreia@mat.ubi.pt