CW Complexes: Products and Quotients

This lecture discusses the construction of CW complexes through characteristic maps, where each map restricts to a homeomorphism onto its image, forming disjoint cells that cover the space. It explores the conditions for a subset to be closed in a CW complex and the verification process for defining a CW complex structure. The lecture also covers the concept of products and quotients of CW complexes, emphasizing the importance of compactness and countable cells. Additionally, it explains how to inherit a CW complex structure in a quotient space from the original space, detailing the formation of new cells in the quotient space.