The Universal Central Extension of the Three-point sl2 Loop Algebra
Abstract
We give a presentation of the universal central extension of the three-point loop algebra L over sl2 by generators and relations. Our presentation arises from the realization of L as the tetrahedron Lie algebra and leads to connections between the universal central extension and the Onsager Lie algebra. Symmetry under the alternating group A4 features prominently in this work.
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