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    Convergence of vector bundles with metrics of Sasaki-type

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    If a sequence of Riemannian manifolds, XiX_i, converges in the pointed Gromov-Hausdorff sense to a limit space, X∞X_\infty, and if EiE_i are vector bundles over XiX_i endowed with metrics of Sasaki-type with a uniform upper bound on rank, then a subsequence of the EiE_i converges in the pointed Gromov-Hausdorff sense to a metric space, E∞E_\infty. The projection maps πi\pi_i converge to a limit submetry π∞\pi_\infty and the fibers converge to its fibers; the latter may no longer be vector spaces but are homeomorphic to Rk/G\R^k/G, where GG is a closed subgroup of O(k)O(k) ---called the {\em wane group}--- that depends on the basepoint and that is defined using the holonomy groups on the vector bundles. The norms μi=∥⋅∥i\mu_i=\|\cdot\|_i converges to a map μ∞\mu_{\infty} compatible with the re-scaling in Rk/G\R^k/G and the R\R-action on EiE_i converges to an R−\R-action on E∞E_{\infty} compatible with the limiting norm. In the special case when the sequence of vector bundles has a uniform lower bound on holonomy radius (as in a sequence of collapsing flat tori to a circle), the limit fibers are vector spaces. Under the opposite extreme, e.g. when a single compact nn-dimensional manifold is re-scaled to a point, the limit fiber is Rn/H\R^n/H where HH is the closure of the holonomy group of the compact manifold considered. An appropriate notion of parallelism is given to the limiting spaces by considering curves whose length is unchanged under the projection. The class of such curves is invariant under the R\R-action and each such curve preserves norms. The existence of parallel translation along rectifiable curves with arbitrary initial conditions is also exhibited. Uniqueness is not true in general, but a necessary condition is given in terms of the aforementioned wane groups GG.Comment: 44 pages, 1 figure, in V.2 added Theorem E and Section 4 on parallelism in the limit space
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