Paper 3, Section II, G

Algebraic Topology | Part II, 2016

Construct a space XX as follows. Let Z1,Z2,Z3Z_{1}, Z_{2}, Z_{3} each be homeomorphic to the standard 2-sphere S2R3S^{2} \subseteq \mathbb{R}^{3}. For each ii, let xiZix_{i} \in Z_{i} be the North pole (1,0,0)(1,0,0) and let yiZiy_{i} \in Z_{i} be the South pole (1,0,0)(-1,0,0). Then

X=(Z1Z2Z3)/X=\left(Z_{1} \sqcup Z_{2} \sqcup Z_{3}\right) / \sim

where xi+1yix_{i+1} \sim y_{i} for each ii (and indices are taken modulo 3 ).

(a) Describe the universal cover of XX.

(b) Compute the fundamental group of XX (giving your answer as a well-known group).

(c) Show that XX is not homotopy equivalent to the circle S1S^{1}.

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