Arens square
In mathematics, the Arens square is a topological space, named for Richard Friederich Arens. Its role is mainly to serve as a counterexample. Definition. The Arens square is the topological space formula_1 where The topology formula_3 is defined from the following basis. Every point of formula_4 is given the local basis of relatively open sets inherited from the Euclidean topology on formula_5. The remaining points of formula_6 are given the local bases Properties. The space formula_10 is: