Contents

# Contents

## Idea

The operations on an H-space $X$ equip its homology with the structure of ring. At least for ordinary homology this is known as the Pontrjagin ring $H_*(X)$ of $X$.

## Properties

The homological version of the group completion theorem relates the Pontrjagin ring of a topological monoid $A$ to that of its group completion $\Omega B A$.