An infinite rank affine Lie algebra g is a Kac-Moody algebra associated with an infinite affine matrix. For each nonnegative integer l, g contains a subalgebra g(l) which is a classical finite dimensional simple Lie algebra, g(0) subset of g(1) subset of ... and g is the inductive limit of the set (g(i), i = 0, 1, ...} of these subalgebras. In the present article, we will determine all automorphisms of g leaving g(ni) invariant for each n(i) in a set {n(i)}, where the set {n(i), i = 1, 2....) is any given nonnegative integer sequence with n(i) < n(2) < .... These automorphisms are generalizations of automorphisms of classical finite dimensional Lie algebras.
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