Paper 4, Section II, G

Algebraic Topology
Part II, 2016

Let T=S1×S1T=S^{1} \times S^{1} be the 2-dimensional torus, and let XX be constructed from TT by removing a small open disc.

(a) Show that XX is homotopy equivalent to S1S1S^{1} \vee S^{1}.

(b) Show that the universal cover of XX is homotopy equivalent to a tree.

(c) Exhibit (finite) cell complexes X,YX, Y, such that XX and YY are not homotopy equivalent but their universal covers X~,Y~\widetilde{X}, \widetilde{Y}are.

[State carefully any results from the course that you use.]