Abstract:
The fractional linear action of $\mathrm{SO}(3,3)$ on the projective space $\mathrm{SO}(3)$ is proven to be a (globally defined) projective action.
Key words and phrases:$2$-cover of $\mathrm{SO}(3,3)$ by $\mathrm{SL}(4)$, fractional linear action of $\mathrm{SO}(3,3)$ on $\mathrm{SO}(3)$, bi-invariant metrics, geodesics, $2$-cover of $S^1\times \mathrm{SO}(3)$ by Segal's compact cosmos $\mathrm{UU}(2)$.