Join (topology)

In the context of topology, a **join** is an operation that combines two topological spaces into a new space. Given two topological spaces \( X \) and \( Y \), the join of \( X \) and \( Y \), denoted \( X * Y \), is constructed in a specific way. The join \( X * Y \) can be visualized as follows: 1. **Take the Cartesian product** \( X \times Y \).