Talk:Fibration

wrong

This is wrong as it stands. Every fiber bundle satisfies the HLP, but not every fibration is a fiber bundle. Serre's classic example, $\Omega X\to PX\to X$ is not a fiber bundle. Michael Larsen 12:25, 16 Sep 2003 (UTC)

Well, that all bundles satisfy the HLP is wrong too, although morally right, as the article now explains.--John Z 06:03, 9 August 2005 (UTC)[reply]

Technical accesibility

I propose adding the following definition for a Serre fibration, which I am taking from Novikov, "Topology I (General Survey)":

Let B some topological space be the base space, and let $A\subset B$ be some subset. Let I=[0,1] be the unit interval and let $\gamma :I\to B$ be some continuous path. The total space E is given by

E=\{\gamma |\gamma (1)\in A\}

That is, the total space E consists of all continuous paths $\gamma :I\to B$ that connect points in A to points in B. The projection $p$ is given by

p(\gamma )=\gamma (0)=x\in B

The fiber over a point $x\in B$ is thus

F_{x}=p^{-1}(x)=\{\gamma |\gamma (0)=x\}

Properties: The total space E contains a copy of A, given by $\gamma (t)=const$ . Thus A is a deformation retract of E. When A consists of a single point $x_{0}\in B$ , then E is contractible. When A consists of a single point $x_{0}\in B$ , the fiber $F_{x}=p^{-1}(x)$ over a point $x\in B$ is commonly denoted by $F_{x}=\Omega (x,x_{0})$ . The fiber $F_{x_{0}}=\Omega (x_{0},x_{0})=\Omega _{x_{0}}B$ over $x_{0}$ is the loop space of B based at $x_{0}$ .

Would this be an acceptable definition of a Serre fibration? I think this is a whole lot easier, and very concrete, as compared to the mumbo-jumbo about CW-complexes; The CW-complex bit is mostly about the categorification of the thing, as best I understand it, and should be held off for later in the article.

I think it also makes the section on the long exact sequence in the article homotopy group less obtuse.

Next: A localy trivial fibration is called a fiber bundle (where we define a locally trivial fibration to the usual definition of being homeomorphic to the direct product of an open set times the fiber. Would that work? I'll try to think up of a really simple illustration of a fibration that is not a fiber bundle. linas 17:56, 16 December 2006 (UTC)[reply]

The above proposal won't work out very well, and here's why: fibrations simply aren't interesting to read about or study, or think about, till some earlier concepts are clearly mastered, such as mapping fiber, mapping cone and homotopy lifting property. The above definition does introduce some of these ideas, albeit poorly. But if those concepts are already mastered, then this article should be fairly accessible. If those concepts are not mastered, there is not much point to understanding a fibration, other than to know that a fiber bundle is a special case. Maybe this article could be expanded, but it would have to be tighter than above. 67.198.37.16 (talk) 04:53, 5 September 2016 (UTC)[reply]

a few suggestions

I think that the second heading "categorical definition" is misleading. Under a "categorical definition" I'd understand a rephrasing of the previous stuff in categorical terms, however this is not what the section gives. Also, the references seem not quite appropriate since all of them refer to fibrations for categories, and not for spaces.

If noone objects, I might try to improve upon these points. - Saibot2 11:54, 17 March 2007 (UTC)[reply]

BTW, what's a "numerable open cover"? - Saibot2 12:08, 17 March 2007 (UTC)[reply]

An open cover is "numerable" if it admits a partition of unity. A fiber bundle is a fibration if it becomes trivial when restricted to the open sets of a numerable open cover. As far as I know, more general locally trivial fiber bundles may not be fibrations in the sense defined in this article! However, I don't know a counterexample! If anyone knows one, please tell me. John Baez (talk) 22:36, 27 January 2008 (UTC)[reply]

Connections to the fibred category article

There is a separate article on fibred category. I propose that this article be renamed "fibration (topology)", and that a redirection notice be included at the top of the article, to guide people to the fibred category article if they want to go there. I would then remove the categorical stuff from this page, which is already on that page. OK? Sam Staton 17:44, 24 October 2007 (UTC)[reply]

I've just done all this, except for the renaming. Would anyone object to that? Would "fibration (algebraic topology)" be better? Sam Staton (talk) 19:02, 20 November 2007 (UTC)[reply]

"Too much jargon"?

I'm surprised to see "This article contains too much jargon" at the top of the page. All the technical terms are linked to explanations, and the level of the article is consistent with other pages on mathematical subjects. I propose to simply remove the "too much jargon" notice, unless anyone has specific suggestions for improving the page. Jowa fan (talk) 02:13, 21 October 2010 (UTC)[reply]

The notice is now gone, you or someone removed it. 67.198.37.16 (talk) 04:54, 5 September 2016 (UTC)[reply]

Example

Unless I'm mistaken, aren't all the given examples of fibrations also fiber bundles? That's not great. Shouldn't there be an example of fibration that is not a fiber bundle? — Preceding unsigned comment added by Seub (talk • contribs) 22:24, 27 May 2020 (UTC)[reply]

Error?

In Fibration#Puppe sequence, the sentence "The inclusion $\Omega B\hookrightarrow F_{p}(\simeq F)$ is a homotopy equivalence" seems wrong: for example, in the case of the Hopf fibration, $\Omega B=\Omega S^{2}$ is not homotopy equivalent to the fibre $F=S^{1}$ . I am also not sure why it's an "inclusion"; if anything it looks more like a projection to me, but I'm not an expert. — ncfavier 12:28, 20 May 2024 (UTC)[reply]

Considering that this seems to be taken from Hatcher [1] (see p.409), I think that

F_{p}

was meant to be

F_{i}

, and the homotopy equivalence with

F

in particular is incorrect. Kdh12 (talk) 21:26, 23 July 2024 (UTC)[reply]

Okay, I've self-appointed as the expert and fixed the mistake. — ncfavier 15:20, 24 July 2024 (UTC)[reply]

What is a 'space' in this article?

A topological space? A manifold? A variety? A subset of Euclidean space? An object in an abstract category?

Please clarify. 98.116.140.24 (talk) 23:44, 27 June 2024 (UTC)[reply]

I can't imagine it being anything other than a topological space in this context. 110521sgl (talk) 12:04, 17 December 2024 (UTC)[reply]

This isn't quite a pullback, right?

In Fibration#puppe_sequence, it says "The mapping $i\colon F_{p}\to E$ with $i(e,\gamma )=e$ , where $e\in E$ and $\gamma \colon I\to B$ is a path from $p(e)$ to $b_{0}$ in the base space, is a fibration. Specifically it is the pullback fibration of the pathspace fibration $PB\to B$ along $p$ ." However, according to the definitions in this article, the pullback map would actually need to take a pair $(e,\gamma )$ as input with $\gamma$ running from $b_{0}$ to $p(e)$ . Swapping the endpoints of every such path doesn't really change anything about the semantics of what we're doing (and seen as $i$ is defined as sending $(e,\gamma )$ to $e$ , modifying $\gamma$ has no effect on the actual fibration either), but it's still a mistake. I just want to have someone else verify my reasoning before I make any changes, because this is a very dense section and in case there are any mistakes on my part, they would likely go unnoticed through multiple further edits, which would be a bit of a pain. 110521sgl (talk) 12:03, 17 December 2024 (UTC)[reply]