Paper 4, Section II, G

Algebraic Topology
Part II, 2009

Let XX be the subset of R4\mathbb{R}^{4} given by X=ABCR4X=A \cup B \cup C \subset \mathbb{R}^{4}, where A,BA, B and CC are defined as follows:

A={(x1,x2,x3,x4)R4:x12+x22+x32+x42=1}B={(x1,x2,x3,x4)R4:x1=x2=0,x32+x421}C={(x1,x2,x3,x4)R4:x3=x4=0,x12+x221}\begin{aligned} &A=\left\{\left(x_{1}, x_{2}, x_{3}, x_{4}\right) \in \mathbb{R}^{4}: x_{1}^{2}+x_{2}^{2}+x_{3}^{2}+x_{4}^{2}=1\right\} \\ &B=\left\{\left(x_{1}, x_{2}, x_{3}, x_{4}\right) \in \mathbb{R}^{4}: x_{1}=x_{2}=0, x_{3}^{2}+x_{4}^{2} \leqslant 1\right\} \\ &C=\left\{\left(x_{1}, x_{2}, x_{3}, x_{4}\right) \in \mathbb{R}^{4}: x_{3}=x_{4}=0, x_{1}^{2}+x_{2}^{2} \leqslant 1\right\} \end{aligned}

Compute H(X)H_{*}(X)