K-theory of the mapping torus of the factor swap on two complex projective planes
= K-theory of the mapping torus of the factor swap on two complex projective planes
{c}
{title2=$K^0(T_{\mathrm{swap}})$}
For the factor swap on $\mathbb{CP}^2\times\mathbb{CP}^2$, the invariant subgroup of
$$
\mathbb Z[x,y]/(x^3,y^3)
$$
has basis $1,xy,x^2y^2,x+y,x^2+y^2,xy^2+x^2y$. Hence the mapping torus has $K^0\cong\mathbb Z^6$.