Paper 4, Section II, G

Metric and Topological Spaces | Part IB, 2019

(a) Define the subspace, quotient and product topologies.

(b) Let XX be a compact topological space and YY a Hausdorff topological space. Prove that a continuous bijection f:XYf: X \rightarrow Y is a homeomorphism.

(c) Let S=[0,1]×[0,1]S=[0,1] \times[0,1], equipped with the product topology. Let \sim be the smallest equivalence relation on SS such that (s,0)(s,1)(s, 0) \sim(s, 1) and (0,t)(1,t)(0, t) \sim(1, t), for all s,t[0,1]s, t \in[0,1]. Let

T={(x,y,z)R3(x2+y22)2+z2=1}T=\left\{(x, y, z) \in \mathbb{R}^{3} \mid\left(\sqrt{x^{2}+y^{2}}-2\right)^{2}+z^{2}=1\right\}

equipped with the subspace topology from R3\mathbb{R}^{3}. Prove that S/S / \sim and TT are homeomorphic.

[You may assume without proof that SS is compact.]

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