697 research outputs found
On Z-graded loop Lie algebras, loop groups, and Toda equations
Toda equations associated with twisted loop groups are considered. Such
equations are specified by Z-gradations of the corresponding twisted loop Lie
algebras. The classification of Toda equations related to twisted loop Lie
algebras with integrable Z-gradations is discussed.Comment: 24 pages, talk given at the Workshop "Classical and Quantum
Integrable Systems" (Dubna, January, 2007
On Z-gradations of twisted loop Lie algebras of complex simple Lie algebras
We define the twisted loop Lie algebra of a finite dimensional Lie algebra
as the Fr\'echet space of all twisted periodic smooth mappings
from to . Here the Lie algebra operation is
continuous. We call such Lie algebras Fr\'echet Lie algebras. We introduce the
notion of an integrable -gradation of a Fr\'echet Lie algebra, and
find all inequivalent integrable -gradations with finite dimensional
grading subspaces of twisted loop Lie algebras of complex simple Lie algebras.Comment: 26 page
Enumeration of quarter-turn symmetric alternating-sign matrices of odd order
It was shown by Kuperberg that the partition function of the square-ice model
related to the quarter-turn symmetric alternating-sign matrices of even order
is the product of two similar factors. We propose a square-ice model whose
states are in bijection with the quarter-turn symmetric alternating-sign
matrices of odd order, and show that the partition function of this model can
be also written in a similar way. This allows to prove, in particular, the
conjectures by Robbins related to the enumeration of the quarter-turn symmetric
alternating-sign matrices.Comment: 11 pages, 13 figures; minor correction
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