# Example in topology: quotient maps and arcwise connected

1. Jan 8, 2012

### nonequilibrium

Just to make sure that I'm not overlooking anything, is the following an example of a quotient map $p: X \to Y$ with the properties that Y is pathwise connected (i.e. connected by a continuous function from the unit interval), $\forall y \in Y: p^{-1}(\{ y \}) \subset X$ also pathwise connected and such that X is not connected?

As $X$ take the topologist's sine curve (i.e. the closure of the curvy bit), and simply define p as the projection on the x-axis, such that $Y = [0,1]$ with the quotient topology, which I think coincides with the normal topology on it. By definition of quotient topology, p is a quotient map. Also, Y is pathwise connected and it seems that $\forall y \in [0,1]: p^{-1}(\{ y \})$ is also pathwise connected.

2. Jan 8, 2012

### micromass

Staff Emeritus
Seems ok!!

3. Jan 13, 2012

### Bacle2

Isn't the topologists' sine curve connected? It is the closure of the continuous image of the semi-open interval (0,1]. And the closure of a connected space (which is the definition of the topologists' sine curve that I know of, i.e., the closure of the graph of Sin(1/x) for x in (0,1]) is also connected. AFAIK, the topologists' sine curve is the standard example of connected , but not path-connected.

Last edited: Jan 13, 2012
4. Jan 13, 2012

### micromass

Staff Emeritus
Yeah, it is connected, but not path connected. We were looking for something that wasn't path connected.