A topological problem on quotient spaces involving characteristic functions

67 Views Asked by At

Let $p:( [0,1],T_1) \rightarrow ( \{0,1\},T_2)$ be the quotient map arising from the characteristic function on $[\frac{1}{2},1],$ where $T_1$ is the subspace topology induced on $[0,1]$ from the standard topology on $\mathbb{R}.$

Show the following claims about the quotient map p.

  1. Prove p is an open map. If not, give a counterexample.
  2. Prove p is a closed map. If not, give a counterexample.

Attempt:

The open sets in $T_1$ are of the form

(i) $(a,1],$ where $0 \leq a <1,$

(ii) $[0,b),$ where $0<b \leq 1,$

(iii) $(a,b),$ where $0 \leq a \leq b \leq 1,$

(iv) $\phi$ and the whole space $[0,1].$

Given that p is the characteristic function on $[\frac{1}{2},1].$ So, $$p(x)=\chi_{[\frac{1}{2},1]}= \begin{cases} 1, & x \in [\frac{1}{2},1] \\ 0, & x \in [0,\frac{1}{2}) \\ \end{cases}$$

I think the quotient topology induced on the set $\{ 0,1 \}$ by the quotient map $p$ is discrete topology. But, I am not getting any further ideas on how to go ahead in this problem. Any help would be highly appreciated.