# What are the differences between fiber bundle and sheaf?

They are similar.All contain a map and can define the section,the fiber of the fiber bundle is just like the stalk of the sheaf.But what are the differences between them,maybe sheaf is more abstract and can break down, the fibre bundle is more geometric and must keep itself continue. Any other differences?

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Fibre bundles look the same locally at any point of your space. This does not have to be true for sheaves. –  the L Mar 12 '11 at 10:54
I have been told (but do not understand) that there is an adjunction between the category of presheaves on a topological space and the category of bundles over the space, which restricts to an equivalence of categories between the category of sheaves and the category of étale bundles. –  Zhen Lin Mar 12 '11 at 15:40
a fiber bundle is a local product, and a sheaf of (say rings) is a way of associating rings to the open sets of a space so that inclusions of open sets induce homomorphisms of the respective rings. theyre just different things –  yoyo Mar 12 '11 at 16:13
@yoyo: There are many kinds of sheaves other than sheaves of rings. A fibre bundle gives rise to a sheaf of sections, from which (in reasonable circumstances, and when endowed with the appropriate extra structure) the bundle can be recovered. So, while they are different things, it is not a matter of them being just different things. –  Matt E Mar 12 '11 at 21:11

If $(X,\mathcal{O}_X)$ is a ringed topological space, you can look at locally free sheaves of $\mathcal{O}_X$-modules on $X$.

If $\mathcal{O}_X$ is the sheaf of continuous functions on a topological manifold (=Hausdorff and locally homeomorphic to $\mathbb{R}^n$), or the sheaf of smooth functions on a smooth manifold, you get fiber bundles (the sheaf associated to a fiber bundle is the sheaf of "regular" (=continuous or smooth here) sections).

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... and conversely any fiber bundle has a natural sheaf associated to it, namely the sheaf of sections of the bundle. –  Matt Mar 12 '11 at 19:53

First remark, there is the definition of sheaf from wikipedia (which by the way talks about étalé spaces and that adjunction business) and the équivalent one 1.2. p. 3 of Bredon, Glen E. (1997), "Sheaf theory" which looks much more like that of a bundle (the A in that definition is the étalé space).

The second remark (from this p.2-3) is that a bundle is locally homeomorphic to a cartesian product, whereas a sheaf is locally homeomorphic to the "base space" itself!

Other difference is that a manifold (which a bundle is) is Hausforff, not the étalé space.

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