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In mathematics, specifically in algebraic topology and algebraic geometry, an inverse image functor is a contravariant construction of sheaves; here “contravariant” in the sense given a map :, the inverse image functor is a functor from the category of sheaves on Y to the category of sheaves on X.
The notion of pullback as a fiber-product ultimately leads to the very general idea of a categorical pullback, but it has important special cases: inverse image (and pullback) sheaves in algebraic geometry, and pullback bundles in algebraic topology and differential geometry. See also: Pullback (category theory) Fibred category; Inverse image sheaf
More generally, any covariant tensor field – in particular any differential form – on may be pulled back to using . When the map ϕ {\displaystyle \phi } is a diffeomorphism , then the pullback, together with the pushforward , can be used to transform any tensor field from N {\displaystyle N} to M {\displaystyle M} or vice versa.
In this case E 1 × E 2 is a fiber bundle over B × B, and pulling back along the diagonal map B → B × B gives a space homeomorphic (diffeomorphic) to E 1 × B E 2, which is a fiber bundle over B. The pullback of two smooth transverse maps into the same differentiable manifold is also a differentiable manifold, and the tangent space of the ...
Any section s of E over B induces a section of f * E, called the pullback section f * s, simply by defining (′):= (′, ((′)) ) for all ′ ′.If the bundle E → B has structure group G with transition functions t ij (with respect to a family of local trivializations {(U i, φ i)}) then the pullback bundle f * E also has structure group G.
The reconstruction of an image from the acquired data is an inverse problem. Often, it is not possible to exactly solve the inverse problem directly. In this case, a direct algorithm has to approximate the solution, which might cause visible reconstruction artifacts in the image. Iterative algorithms approach the correct solution using multiple ...
Don't re-upload the image—just edit the image description page and add the licensing information! Also, the wiki software can change the display size of the images, so you do not need to re-upload a smaller version of the same image to use a smaller version in an article. See Wikipedia:Extended image syntax. There, you can learn how to use ...
Tomographic reconstruction: Projection, Back projection and Filtered back projection. Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projections. The mathematical basis for tomographic imaging was laid down by Johann Radon.