ThmDex – An index of mathematical definitions, results, and conjectures.
Set of symbols
Alphabet
Deduction system
Theory
Zermelo-Fraenkel set theory
Set
Subset
Power set
Hyperpower set sequence
Hyperpower set
Hypersubset
Subset algebra
Topology
Bottom topology
Bottom topological space
Definition D1112
Empty topological space
Formulation 0
Let $\emptyset$ be the D13: Empty set.
A D548: Ordered pair $T = (X, \mathcal{T})$ is an empty topological space if and only if
(1) $X = \emptyset$
(2) $\mathcal{T} = \{ \emptyset \}$