Normal Space is Preserved under Homeomorphism

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Theorem

Let $T_A = \struct {S_A, \tau_A}$ and $T_B = \struct {S_B, \tau_B}$ be topological spaces.

Let $\phi: T_A \to T_B$ be a homeomorphism.


If $T_A$ is a normal space, then so is $T_B$.


Proof

We have that $\struct {S, \tau}$ is a normal space if and only if:

$\struct {S, \tau}$ is a $T_4$ space
$\struct {S, \tau}$ is a $T_1$ (Fréchet) space.


From $T_4$ Space is Preserved under Homeomorphism:

If $T_A$ is a $T_4$ space, then so is $T_B$.

From $T_1$ Space is Preserved under Homeomorphism:

If $T_A$ is a $T_1$ (Fréchet) space, then so is $T_B$.


Hence the result.

$\blacksquare$


Sources