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while studying some general topology I came across the following topological space: on $\mathbb{R}$ we define an equivalence relation by $x \sim y$ if and only if $x=y$ or $|x|=|y|$ and $x \notin \mathbb{Q}$, and then we set $X=\mathbb{R}/\sim$ with the quotient topology induced by the euclidean one on $\mathbb{R}$.

I was able to prove that it is $T_1$ but not $T_2$, for instance, but then I asked myself whether $X$ is locally path connected or locally connected.

My guess is that the locally path connected claim is true (and hence it implies the other). Indeed, if $p$ denotes the quotient map, for the class of $x \notin \mathbb{Q}$ one can take the image of the union of two balls $$ U_\epsilon(x):=p(B_\epsilon(x)) \cup p(B_\epsilon(-x)) $$ as $\epsilon$ varies. The $U_\epsilon$ are path connected.

But for $x \in \mathbb{Q}$ the same argument does not apply, because for $x \neq 0$ the open subset $U_1(x)\setminus\{[-x]\}$ does not contain any $U_\epsilon(x)$. I think one has to take at least $U_\epsilon(x)$ minus the image via $p$ of any subset of $\mathbb{Q}$ with $-x$ as the only possible accumulation point, but I wonder whether this is correct: they seem to open in the quotient topology, but are enough to build a neighbourhood system?

Pawel02
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    Given a space $X$ and an equivalence relation $\sim,$ the quotient map $X\to X/\sim$ is continuous and onto. And the continuous image of a path-connected space is path-connected. – Thomas Andrews Jul 05 '23 at 21:41
  • That's true. But I am asking about local path connectedness. But! It seems that the quotient of a locally path connected space is still locally path connected, so that solves my question. – Pawel02 Jul 05 '23 at 23:19
  • I suggest you study why the quotient of a path-connected/locally path-connected space still has the same property, if you are not already doing so. It will help you in the future with other properties. – Paul Sinclair Jul 06 '23 at 20:08
  • See https://math.stackexchange.com/questions/2426794/a-quotient-of-a-locally-connected-space-is-locally-connected – ronno Aug 07 '23 at 14:42

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