Pathway XVII

τTopology

Open sets, unions, finite intersections. Compactness is finite subcovers.

1. 01Open setsA topology is a family of opens: empty and whole space, closed under unions and finite intersections.4 min
2. 02CompactnessA set is compact when every open cover has a finite subcover. [0,1] is the prototype.4 min
3. 03The fundamental groupLoops on a space, up to continuous deformation. The circle has π₁ = ℤ — winding number.4 min