ordinary group notation: can be written as , or ; the inverse can be written as or Using the multiplicative notation, the associativity, identity and inverse laws can be rewritten as: , and . The most prominent example of an affine algebraic group is the general linear group of degree This is the group of linear transformations of the vector space if a basis of is fixed, this is equivalent to the group of invertible matrices with entries in It can be shown that any affine algebraic group is isomorphic to a subgroup of . For this reason, affine algebraic groups are often called linear algebraic groups. Affine algebraic groups play an important role in the classification of finite simple groups, as the groups of Lie type are all sets of -rational points of an affine algebraic group, where is a finite field. Generalizations If an author requires the base field of an affine variety to be algebraically closed (as this article does), then irreducible affine algebraic sets over non-algebraically closed fields are a generalization of affine varieties. This generalization notably includes affine varieties over the real numbers. An affine variety plays a role of a local chart for algebraic varieties; that is to say, general algebraic varieties such as projective varieties are obtained by gluing affine varieties. Linear structures that are attached to varieties are also (trivially) affine varieties; e.g., tangent spaces, fibers of algebraic vector bundles. An affine variety is a special case of an affine scheme, a locally-ringed space which is isomorphic to the spectrum of a commutative ring (up to an equivalence of categories). Each affine variety has an affine scheme associated to it: if is an affine variety in with coordinate ring then the scheme corresponding to is the set of prime ideals of The affine scheme has "classical points" which correspond with points of the variety (and hence maximal ideals of the coordinate ring of the variety), and also a point for each closed subvariety of the variety (these points correspond to prime, non-maximal ideals of the coordinate ring). This creates a more well-defined notion of the "generic point" of an affine variety, by assigning to each closed subvariety an open point which is dense in the subvariety. More generally, an affine scheme is an affine variety if it is reduced, irreducible, and of finite type over an algebraically closed field Notes See also