In mathematics, a Hausdorff space X is called a fixed-point space if it obeys a fixed-point theorem, according to which every continuous function f : X → X {\displaystyle f:X\rightarrow X} has a fixed point, a point x {\displaystyle x} for which f ( x ) = x {\displaystyle f(x)=x} . For example, the closed unit interval is a fixed point space, as can be proved from the intermediate value theorem. The real line is not a fixed-point space, because the continuous function that adds one to its argument does not have a fixed point. Generalizing the unit interval, by the Brouwer fixed-point theorem, every compact bounded convex set in a Euclidean space is a fixed-point space. The definition of a fixed-point space can also be extended from continuous functions of topological spaces to other classes of maps on other types of space.
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