Loop algebra

In mathematics, loop algebras are certain types of Lie algebra, of particular interest in theoretical physics.

If <math>mathfrak</math> is a Lie algebra, the tensor product of <math>mathfrak</math> with <math>C^infty(S^1)</math>,

<math>mathfrakotimes C^infty(S^1)</math>,

the algebra of (complex) smooth functions over the circle manifold S¹ is an infinite-dimensional Lie algebra with the Lie bracket given by

<math>=otimes f_1 f_2</math>.

Here g₁ and g₂ are elements of <math>mathfrak</math> and f₁ and f₂ are elements of <math>C^infty(S^1)</math>.

This isn't precisely what would correspond to the direct product of infinitely many copies of <math>mathfrak</math>, one for each point in S¹, because of the smoothness restriction. Instead, it can be thought of in terms of smooth map from S¹ to <math>mathfrak</math>; a smooth parameterized loop in <math>mathfrak</math>, in other words. This is why it is called the loop algebra.

We can take the Fourier transform on this loop algebra by defining

<math>gotimes t^n</math>

as

<math>gotimes e^</math>

where

0 &le; &sigma; <2&pi;

is a coordinatization of S¹.

If...
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