Convergence of Ricci flow solutions to Taub-NUT

We study the Ricci flow starting at an SU(2) cohomogeneity-1 metric $g_{0}$ on $\mathbb{R}^{4}$ with monotone warping coefficients and whose restriction to any hypersphere is a Berger metric. If has bounded Hopf-fiber, curvature controlled by size of orbits opens faster than paraboloid in directions orthogonal then converges Taub-NUT $g_{\mathsf{TNUT}}$ Cheeger-Gromov sense infinite time. also classify long-time behaviour when asymptotically flat. In order identify infinite-time singularity models we obtain uniqueness result for $g_{\mathsf{TNUT}}$.