# algebraic topology – Example of a particular prime point/prime end.

I was reading the following article:

https://arxiv.org/pdf/math/0303258.pdf

And at some point there’s the definition of a set X(e), as follows:

The set of principal points of chains Ω ∈ e is called the principal set of
e, which we denote by X(e).

I was trying to come up with an example of a prime point e that X(e) is not a single point. As far as could get by myself, this prime point will probably be a prime end.

Hope somebody can help me with this.