=====T0-spaces===== Abbreviation: **Top$_0$** ====Definition==== A \emph{$T_0$-space} is a [[topological spaces]] $\mathbf{X}=\langle X,\Omega(\mathbf{X})\rangle$ such that for every pair of distinct points in the space, there is an open set containing one but not the other: $x,y\in X\Longrightarrow\exists U\in\Omega(\mathbf{X})[(x\in U\mbox{ and }y\notin U)\mbox{ or }(y\in U\mbox{ and }x\notin U)]$ ==Morphisms== Let $\mathbf{X}$ and $\mathbf{Y}$ be $T_0$-spaces. A morphism from $\mathbf{X}$ to $\mathbf{Y}$ is a function $f:X\rightarrow Y$ that is \emph{continuous}: $V\in\Omega(\mathbf{Y})\Longrightarrow f^{-1}[V]\in\Omega(\mathbf{X})$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |second-order | ^[[Amalgamation property]] |yes | ^[[Strong amalgamation property]] |no | ^[[Epimorphisms are surjective]] |no | Remark: The properties given above use an $(\mathcal{E},\mathcal{M})$ factorization system with $\mathcal{E}=$ surjective morphisms and $\mathcal{M}=$ embeddings. ====Subclasses==== [[T1-spaces]] ====Superclasses==== [[Topological spaces]] see also http://www.wikipedia.org/wiki/Topology_glossary ====References==== [(Ln19xx> )]\end{document} %