Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2017/iii/paper-115/1/c/solution

A vector bundle morphism over is a smooth map with whose restriction is linear for every . A vector bundle isomorphism is such a map with a smooth bundle-morphism inverse. Equivalently, a fiberwise bijective smooth bundle morphism is an isomorphism: in local vector bundle trivializations it is multiplication by an invertible smooth matrix, and its inverse matrix is smooth.
For a diffeomorphism , define
The derivative is a linear isomorphism by the chain rule, since . In manifold charts, is represented by the smooth Jacobian matrix of , so it is a smooth bundle morphism. Its inverse is
which is also smooth and fiberwise linear. Consequently
This identifies the bundles over the same base ; the tangent map by itself is a map from to covering .

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