Uniform algebra

In functional analysis, a uniform algebra A on a compact Hausdorff topological space X is a closed (with respect to the uniform norm) subalgebra of the C*-algebra C(X) (the continuous complex-valued functions on X) with the following properties:
 * the constant functions are contained in A
 * for every x, y $$\in$$ X there is f$$\in$$A with f(x)$$\ne$$f(y). This is called separating the points of X.

As a closed subalgebra of the commutative Banach algebra C(X) a uniform algebra is itself a unital commutative Banach algebra (when equipped with the uniform norm). Hence, it is, (by definition) a Banach function algebra.

A uniform algebra A on X is said to be natural if the maximal ideals of A are precisely the ideals $$M_x$$ of functions vanishing at a point x in X.

Abstract characterization
If A is a unital commutative Banach algebra such that $$||a^2|| = ||a||^2$$ for all a in A, then there is a compact Hausdorff X such that A is isomorphic as a Banach algebra to a uniform algebra on X. This result follows from the spectral radius formula and the Gelfand representation.