Questions tagged [fibration]

For questions about or involving fibrations which are maps which satisfy the homotopy lifting property for all spaces.

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Flatness in Algebraic Geometry vs. Fibration in Topology

I am currently trying to get my head around flatness in algebraic geometry. In particular, I'm trying to relate the notion of flatness in algebraic geometry to the notion of fibration in algebraic ...
Daniel Loughran's user avatar
38 votes
1 answer
2k views

Is an affine fibration over an affine space necessarily trivial?

Let $X$ be an algebraic variety over an alg. closed field with zero char. and let $f:X\to \mathbb{A}^n$ be a smooth surjective morphism, such that all fibers (at closed points) are isomorphic to $\...
KotelKanim's user avatar
  • 2,007
30 votes
3 answers
2k views

Is the counit of geometric realization a Serre fibration?

Recall that a Serre fibration between topological spaces is a map which has the homotopy lifting property (HLP) for all CW complexes (equivalently for all disks $D^k$). The Serre fibrations are the ...
Chris Schommer-Pries's user avatar
23 votes
2 answers
4k views

construct the elliptic fibration of elliptic k3 surface

Hi all, As we know, every elliptic k3 surface admits an elliptic fibration over $P^1$, but generally how do we construct this fibration? For example, how to get such a fibration for Fermat quartic? ...
Jay's user avatar
  • 583
20 votes
1 answer
804 views

Are all homotopy equivalences realized by fibrations over [0,1]?

Given two homotopy equivalent spaces $X$ and $Y$, does there always exist a Hurewicz fibration $p: E\rightarrow [0,1]$ with $p^{-1} (0) = X$ and $p^{-1} (1)=Y$? This issue shows up in the accepted ...
Dan Ramras's user avatar
  • 8,498
17 votes
6 answers
5k views

Cohomology of fibrations over the circle

Are there any general results on the (integral) cohomology of manifolds that are fibrations over the circle? Any literature references much appreciated.
Dan's user avatar
  • 273
17 votes
6 answers
2k views

A conceptual proof that local fibrations over paracompact spaces are global fibrations?

I'm teaching some homotopy theory at the moment, and I'm discovering a number of things I've never before learned properly. (I guess everybody who's ever taught knows that feeling.) One of those ...
Tilman's user avatar
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15 votes
4 answers
4k views

What does it mean to speak of a homotopy fibration sequence?

I'm reading a paper in which the following is done. We have a certain particular map of spaces $f:X\to Y$ and then it is said something along the lines of "let $Z_f$ denote the space whose defining ...
Bruno Stonek's user avatar
  • 2,914
15 votes
2 answers
1k views

Where does the primary obstruction of a fibration show up in its spectral sequence?

Let $f\colon\thinspace E\to B$ be a Serre fibration whose fibre $F$ is $k-1$-connected, $k\geq 1$. Assume $B$ is a connected CW complex. Then the primary obstruction to the existence of a cross ...
Mark Grant's user avatar
14 votes
3 answers
3k views

Multiplicativity of Euler characteristic for non-orientable fibrations

Let $E\to B$ be a fibration with fiber F, and assume for simplicity that B is connected. Suppose moreover that B and F have Euler characteristics (perhaps they are manifolds). Then often, one can ...
Mike Shulman's user avatar
13 votes
2 answers
2k views

Request: A Serre fibration that is not a Dold fibration

A Serre fibration has the homotopy lifting property with respect to the maps $[0,1]^n \times \{0\} \to [0,1]^{n+1}$. A Dold fibration $E \to B$ has the weak covering homotopy property: lifts with ...
David Roberts's user avatar
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13 votes
2 answers
858 views

is there any fibration $\mathbb{R}^n\to \mathbb{S}^n$?

It is probably a trivial question. But I don't see the answer. Is there any Hurewicz fibration $\mathbb{R}^n\to \mathbb{S}^n$ ? Is there any fibration $X\to \mathbb{S}^n$, when $X\subset \mathbb{R}^...
Fernando's user avatar
  • 865
13 votes
2 answers
2k views

Pull-back of a fibration along a homotopy equivalence and homotopy classes of sections

I previously asked this on Math.SE but didn't receive a satisfactory answer. Let $p:E\rightarrow B$ be a fibration (i.e. have the homotopy lifting property with respect to all spaces), and $f: B'\...
user46652's user avatar
  • 655
12 votes
3 answers
1k views

Classifying space for fibrations with Eilenberg-MacLane space fibers and nontrivial fundamental group actions

Let $A$ be an abelian group and let $n \geq 2$. For any connected CW complex $X$, it is standard that a fibration $f\colon E \rightarrow X$ whose fibers are homotopy equivalent to a $K(A,n)$ is ...
Tina's user avatar
  • 373
12 votes
2 answers
799 views

global fibrations of simplicial sheaves

I'm reading the classical Brown-Gersten's paper "Algebraic K-theory as generalized sheaf cohomology" and I'm stuck with their choose of global fibrations. Namely, a morphism of simplicial sheaves $p : ...
Agustí Roig's user avatar
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12 votes
1 answer
859 views

What is the difference between internal presheaves and presheaves on a total space?

Suppose that $\mathbb{C}$ is a category with finite limits and that $\mathcal{D}$ is a category internal to $\mathbb{C}$. We can also represent $\mathcal{D}$ as a fibration $\mathbb{D}\to\mathbb{C}$. ...
user35952's user avatar
  • 121
11 votes
3 answers
906 views

Can Homotopy Type Theory or algebraic geometry deal with homotopy fibers in terms of families?

((In conclusion) It was hard to choose which answer to accept. I decided for the one which addressed most of the various aspects of the question. ) (Later addon) I now decided to put a bounty on ...
მამუკა ჯიბლაძე's user avatar
11 votes
1 answer
480 views

Which maps of simplicial sets geometrically realize to fibrations?

If $f:X\to Y$ is a Kan fibration of simplicial sets, then its geometric realization $|f| : |X|\to |Y|$ is (in some suitable convenient category of topological spaces, like compactly generated ones) a ...
Mike Shulman's user avatar
11 votes
0 answers
263 views

Madsen-Tillmann spectrum $MTE$ of the group $E$ which is defined in Freed-Hopkins's paper

In Freed-Hopkins's paper, the group $E(d)$ is defined to be the subgroup of $O(d)\times\mathbb{Z}_4$ consisting of the pairs $(A,j)$ such that $\det A=j^2$, where $\mathbb{Z}_4=\{\pm1,\pm\sqrt{-1}\}$ ...
Borromean's user avatar
  • 1,319
10 votes
2 answers
1k views

cup product and Steenrod operations in Serre spectral sequence

Let $F\to E\to B$ be a fibration with $B$ simply-connected. Suppose all differentials in the cohomology Serre spectral sequence (corresponding to the above fibration) are zero maps. Then as a graded ...
QSR's user avatar
  • 2,213
10 votes
2 answers
822 views

Uniformization of Kodaira fibered surfaces

Consider a Kodaira fibration. i.e. a smooth non-isotrivial fibration $X\rightarrow C$ with $X$ a smooth complex surface and $C$ a smooth complex curve, such that both the genus of $C$ and genus of the ...
Darius Math's user avatar
  • 2,181
10 votes
2 answers
273 views

Reference request - Fibrations between spaces of embeddings

This is a cross-post of this question from MSE. Given topological manifolds $M$ and $N$ of the same dimension, let $\operatorname{Emb}(M,N)$ denote the subspace of $\operatorname{Map}(M,N)$ ...
Ken's user avatar
  • 1,749
10 votes
1 answer
498 views

Bundle-to-function correspondence

To a morphism of sets $f\colon E\to B$ with finite fibers, one may assign a function $$|f^{-1}|\colon B\to{\mathbb N}$$ sending an element $b\in B$ to the cardinality of the fiber $f^{-1}(b)$. To a ...
David Spivak's user avatar
  • 8,549
9 votes
1 answer
2k views

How to Compute Transgressions in a Serre Spectral Sequence?

For a short exact sequence of groups $1\rightarrow A\rightarrow B\rightarrow C\rightarrow 1$ there is an associated fibration $K(A,1)\rightarrow K(B,1)\rightarrow K(C,1)$, which can be constructed by ...
Zuriel's user avatar
  • 1,098
9 votes
4 answers
681 views

Pullback-stable model of fibrewise suspension of fibrations (in simplicial sets, or similar setting)

Given a fibration $p : Y \to X$ in simplicial sets (or any other model category), there are various ways to construct its fibrewise suspension, i.e. its suspension as an object of the slice $\...
Peter LeFanu Lumsdaine's user avatar
9 votes
1 answer
989 views

Calabi-Yau fiber space without singular fibers implies finite quotient of product?

While reading this paper of Kollár, the following question came up. If $f:X\to Y$ is a fiber space (i.e. surjective holomorphic map with connected fibers) with $X,Y$ smooth projective manifolds,...
9 votes
1 answer
502 views

When is $X_{hG} \to X/G$ a weak equivalence for $X$ a free $G$-space, $G$ compact Lie?

Two questions (more details below): Let $G$ be a compact Lie group and $X$ a $G$-space such that all stabilizer subgroups are conjugate to a fixed $H \leq G$. Denote by $\pi: X \to X/G$ the quotient ...
Alexander Körschgen's user avatar
9 votes
1 answer
548 views

Homotopical interpretation of flatness?

I have read a discussion (in a less common language) which discussed a homotopical interpretation of flatness, which went something like: A map of commutative algebras is flat if pushing it out ...
Arrow's user avatar
  • 10.3k
8 votes
2 answers
241 views

Is the fiberwise suspension of a Serre fibration a Serre fibration?

Let $\pi\colon X \rightarrow Y$ be a Serre fibration. Define $\Sigma_f\pi \colon \Sigma_f X \rightarrow Y$ be the fiberwise unreduced suspension of $\pi$. Thus $\Sigma_f X = X \times [0,1] / {\sim}$,...
Lauren's user avatar
  • 83
8 votes
1 answer
630 views

Obstructions for the lifting problem after a pull-back

This is a cross-post from a MSE question which received no answers. Beware that the notation here is a little different. Consider the following lifting problem(s): $\require{AMScd}$ \begin{CD} &...
Cihan's user avatar
  • 1,586
8 votes
2 answers
467 views

Constructively, are all fibrations cloven?

A "cloven fibration" is a fibration for which we have an explicit choice of cartesian liftings; this is often phrased as, "We can pick a lifting without using the axiom of choice". Firstly, I'm a bit ...
Jonathan Sterling's user avatar
8 votes
2 answers
862 views

Circle Action on Quaternionic Projective Space

Quoting from Wikipedia article on quaternionic projective space: Therefore the quotient manifold $$ \mathbb{HP}^{2}/\mathrm{U}(1) $$ may be taken, writing $U(1)$ for the circle group. It has ...
Noel Brown's user avatar
8 votes
1 answer
558 views

About fibrations with fibre Eilenberg-MacLane spaces

Let $f: E\rightarrow B$ be a Kan fibration between pointed connected Kan complexes with fibre the Eilenberg-MacLane space $\mathrm{K}(M, n), n\geq 2, M$ an abelian group. Assume $f$ induces an ...
Lao-tzu's user avatar
  • 1,856
8 votes
1 answer
376 views

Elementary computation of direct image sheaves.

I am a physicist and would like to understand the section 1 of this math paper, which explains how the SYZ conjecture implies topological mirror symmetry. I have some technical problem and would ...
Gavin's user avatar
  • 83
8 votes
0 answers
148 views

Mapping classes as Lefschetz fibrations over surfaces with positive genus

Let $\Sigma_{g,r}$ be the surface of genus $g$ and $r$ boundary components. It is known that, from a positive factorization of a mapping class $\phi$ in the mapping class group $MCG(\Sigma_{g,r}, \...
Paul's user avatar
  • 1,379
8 votes
0 answers
593 views

Global geometry of discriminant locus

Let $X$ be a smooth projective threefold, and $\pi : X \to S$ an elliptic fibration over a surface (i.e. flat, with general fiber an elliptic curve). I'm interested in constructing such fibrations ...
user avatar
7 votes
2 answers
328 views

Foliation of $\mathbb R^n$ by connected compact manifolds

Does there exist a smooth nontrivial fiber bundle $p: F \hookrightarrow \mathbb R^n \to B$ such that $F$ and $B$ are connected manifolds with $F$ compact? "Nontrivial" here means the fiber $F$ is not ...
Totoro's user avatar
  • 2,515
7 votes
1 answer
2k views

Quasi-unipotent monodromy for general families

This must be a naive question, but I'm wondering about the definition of quasi-unipotent monodromy for general families, not only 1-parameter families. The problem is that usually, in the books of ...
Jack's user avatar
  • 637
7 votes
1 answer
407 views

A fibration equivalent to having a terminal object

It is well known that the codomain functor $$cod:\mathcal{C}^\to\to\mathcal{C}$$ from the arrow category of a category $\mathcal{C}$ to itself is a fibration iff $\mathcal{C}$ has binary pullbacks. ...
Alec Rhea's user avatar
  • 8,977
7 votes
3 answers
884 views

A fibrant-objects structure on Top

(Sorry for the crossposting, but I'm really interested in this question). One can define (Paragraph 1.5, page 10) a fibrant-object structure on a suitable cartesian closed category of topological ...
fosco's user avatar
  • 13k
7 votes
1 answer
619 views

Where is simpleness used in the proof of existence of Postnikov towers of principal fibrations?

I've read one proof, rather long, in Allen Hatcher's book. There the key is Lemma 4.70, which uses the relative Hurewicz Theorem. But there is another, shorter proof in J.P.May's book "A concise ...
Alexei's user avatar
  • 73
7 votes
1 answer
491 views

Replacing the Fibre of a Fibration

This was a question I first asked on stack exchange, here. In my head it seems like a fairly reasonable thing to ask for, but I'm not aware of any construction in the literature. Let $p:E\rightarrow ...
Tyrone's user avatar
  • 5,016
7 votes
1 answer
426 views

Examples of smooth Hurewicz fibrations which are not smooth fiber bundles

In the category of smooth manifolds (without corners), what are some examples of Hurewicz fibrations which are not fiber bundles? The minimal topological example I know is to project the standard 2-...
Arrow's user avatar
  • 10.3k
7 votes
1 answer
564 views

$\Pi$, $\Sigma$, and identity types without $\eta$ in comprehension categories

In comprehension categories, dependent sums are defined as a choice of left adjoints for all reindexing functors along display maps, satisfying a Beck-Chevalley condition. Dependent products are ...
Paolo Capriotti's user avatar
7 votes
0 answers
639 views

Given a Serre fibration between manifolds, how ugly can it be?

A Serre fibration is clearly defined with motivation from homotopy theory, but we can consider smooth versions $f\colon M\to N$ in the category of (finite-dimensional, paracompact etc) smooth ...
David Roberts's user avatar
  • 33.8k
6 votes
5 answers
2k views

Examples of Riemannian Submersions

Is there any example of a Riemannian submersion, which is no fibration? As far as I know, a (any) submersion is locally, but not globally, given by a fibration. The converse holds globally. ...
Henry Wegener's user avatar
6 votes
3 answers
3k views

The fiber of a Serre fibration

If $p:E\to B$ is a Serre fibration (assume it is surjective), then for each $b\in B$ we get a comparison map $p^{-1}(b) \to F_b$, where $F_b$ is the homotopy fiber of $p$ over $b$. It is easy to ...
Jeff Strom's user avatar
  • 12.5k
6 votes
2 answers
346 views

Space of sections of a fibration under weak homotopy equivalence

If I have two (Serre-)fibrations over the same base, and a weak equivalence of the total spaces that is also a map over the base, could I hope that the induced map on the spaces of sections would also ...
Amueller's user avatar
  • 263
6 votes
1 answer
823 views

Shafarevich conjecture for abelian varieties

In the paper "Arakelov's theorem for abelian varieties" Faltings proves the Shafarevich conjecture for abelian varieties. The statement is the following: Let B be smooth projective a curve, S a ...
Ginevra Carbone's user avatar
6 votes
2 answers
1k views

Action of fundamental group on homotopy fiber

For a Serre fibration of pointed topological spaces $f:X \to B$, there is an action of $\pi_1\left(B,b_0\right)$ on the fiber $F$. The construction of this action I'm familiar with uses a lift $F\...
E. KOW's user avatar
  • 732