Submersion is a smooth and surjective differential map between differentiable manifolds, where the differential at each point is surjective. This concept is vital in understanding how one manifold can be 'mapped down' onto another, preserving certain geometric structures. Submersions are particularly important in the context of studying Riemannian submersions and the behavior of embedded and immersed submanifolds, as they provide insights into how different geometric properties interact when transitioning from one manifold to another.
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