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YouTube Videos – Commutative ring and Related Articles

Spec (Z) contains a point for the zero ideal. The closure of this point is the entire space. The remaining points are the ones corresponding to ideals (p), where p is a prime number. These points are closed.

The twisted cubic (green) is a set-theoretic complete intersection, but not a complete intersection.

A pair of pants is a cobordism between a circle and two disjoint circles. Cobordism classes, with the cartesian product as multiplication and disjoint union as the sum, form the cobordism ring.

Image: Tensor product of algebras