hausdorff_spaces - MathStructures

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=====Hausdorff spaces=====

Abbreviation: **Haus**

====Definition====
A \emph{Hausdorff space} or \emph{$T_2$-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 a pair of disjoint open sets containing each point:  $x,y\in X\Longrightarrow\exists U,V\in\Omega(\mathbf{X})[x\in U\mbox{ and }y\in V\mbox{ and }U\cap V=\emptyset]$

==Morphisms==
Let $\mathbf{X}$ and $\mathbf{Y}$ be Hausdorff 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]]  |no |
^[[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====
[[Compact Hausdorff spaces]] 

[[Completely Hausdorff spaces]] 


====Superclasses====
[[T1-spaces]] 



see also http://www.wikipedia.org/wiki/Hausdorff_space


====References====

[(Ln19xx>
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