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Consider a sequence of pointed n–dimensional complete Riemannian
manifolds {(Mi,gi(t),Oi)} such that
t in [0,T] are solutions
to the Ricci flow and gi(t) have uniformly bounded curvatures and
derivatives of curvatures. Richard Hamilton showed that if the initial
injectivity radii are uniformly bounded below then there is a subsequence
which converges to an n–dimensional solution to the Ricci flow. We
prove a generalization of this theorem where the initial metrics may
collapse. Without injectivity radius bounds we must allow for convergence
in the Gromov–Hausdorff sense to a space which is not a manifold but
only a metric space. We then look at the local geometry of the limit to
understand how it relates to the Ricci flow.
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