In geometry, the Peano curve
is the first example of a space-filling curve to be discovered, by Giuseppe Peano in 1890. Peano's curve is dense in the unit square, and was used by Peano to construct a continuous function from the unit interval to the unit square, motivated by an earlier result of Georg Cantor that these two sets have the same cardinality. Because of this example, some authors use the phrase "Peano curve" to refer more generally to any space-filling curve.To learn how big infinity really is, and more about George Cantor, check this out
.In topology and related branches of mathematics, a Hausdorff space
, separated space or T2
space is a topological space in which distinct points have disjoint neighborhoods. Of the many separation axioms that can be imposed on a topological space, the "Hausdorff condition" (T2
) is the most frequently used and discussed. It implies the uniqueness of limits of sequences, nets, and filters. Hausdorff spaces are named after Felix Hausdorff, one of the founders of topology. Hausdorff's original definition of a topological space (in 1914) included the Hausdorff condition as an axiom.