## Tags » Hurewicz Theorem

#### The augmentation ideal of a group ring

Lemma. Let be a commutative ring and let be a group. We define the map by

Then is an onto ring homomorphism and is a basis for the free -module… 217 more words

Noncommutative Ring Theory Notes

#### 285G, Lecture 5: Finite time extinction of the third homotopy group, I

In the previous lecture, we saw that Ricci flow with surgery ensures that the second homotopy group became extinct in finite time (assuming, as stated in the above erratum, that there is no embedded with trivial normal bundle). 2,100 more words

Math.DG