The category of finite dimensional (type 1) representations of a quantum affine algebra U q(ĝ) is not semisimple. However, as any abelian category with finite-length objects, it admits a unique decomposition in a direct sum of indecomposable subcategories (blocks). We define the elliptic central character of a finite dimensional (type 1) representation of U q(ĝ) and show that the block decomposition of this category is parametrized by these elliptic central characters. © Copyright 2005, American Mathematical Society.7346373Akasaka, T., Kashiwara, M., Finite dimensional representations of quantum affine algebras (1997) Publ. Res. Inst. Math. Sci., 33 (5), pp. 839-867. , MR 99d:17017Beck, J., Braid group action and quantum affine algebras (19...