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The study of differentiable manifolds and differentiable maps. One fundamental problem is that of classifying manifolds up to diffeomorphism. Differential topology is what Poincaré understood as topology or “analysis situs”.

2 votes
1 answer
190 views

Uniform smoothness of locally-flat loops

Let M be a smooth Riemannian manifold. Let $f:S^1\to M$ be a locally-flat injective loop. Must there exist such $\varepsilon>0$ that if we connect points $f(0),f(\varepsilon), f(2\varepsilon)... , f([ …
Nikita Kalinin's user avatar
0 votes

degenerating immersion

The answer is no. Two 2-dim smooth immersed in $\mathbb R^3$ objects generically intersect by line, so if intersection is a point then it can be eliminated. But it is clear that near $z^2$ there are n …
Nikita Kalinin's user avatar
0 votes
2 answers
353 views

Realisability cohomological class as product or as immersed sphere

Let's consider closed simply connected manifold $M^n$ and a $a\in H^k(M)$ and $a*\in H^{n-k}(M)$ is the dual to $a$. Is it true that dual to $a$ is realisable as a immersed sphere or $ a*=bc $ for s …
Nikita Kalinin's user avatar
6 votes
Accepted

Pairing used in Lefschetz duality

Yes, your formula is right. For the intuitive understanding just compute it for 1- and 2- dimensional half-spaces. See Bott & Tu, Differential forms in Algebraic topology, $\S 5$, Poincaré duality. …
Nikita Kalinin's user avatar
3 votes
2 answers
299 views

Discriminant locus in knot space

Consider the space $K$ of all immersions of $S^1$ into $\mathbb R^3$. The set of knots with self-intersection is a discriminant in $K$ and divide it into "chambers". Let $f$ be a knot with $n$ double …
Nikita Kalinin's user avatar
2 votes
1 answer
425 views

Stable singularities of smooth map $\mathbb R^3\to \mathbb R^4$

Does anybody know any classification of stable singularities of smooth map $f:\mathbb R^3\to \mathbb R^4$? It is clear that there are singularities which look like intersection of 2 (or 3 or 4) hyper …
Nikita Kalinin's user avatar
1 vote

Thom polynomial for contact algebraic structures

there is an article of Quo-Shin Chi "The dimension of the moduli space of superminimal surfaces of a fixed degree and conformal structure in the 4-sphere" where the dimension of contact curves moduli …
Nikita Kalinin's user avatar
5 votes
3 answers
595 views

Thom polynomial for contact algebraic structures

Let's consider a algebraic contact structure $P$ on $\mathbb CP^3$ and a algebraic curve $C$ degree $d$ and genus $g$. Let's assume that contact structure has degree $p$ (see Polynomial contact struct …
Nikita Kalinin's user avatar
10 votes
2 answers
891 views

Sum of two tangent bundles of $S^{2n}$

I was wondering if the sum $TS^{2n}\oplus TS^{2n}$ is a trivial bundle? The same is true for spheres of odd dimension (one can find a nowhere zero section of the second bundle, add it to the first, th …
Nikita Kalinin's user avatar
3 votes
1 answer
435 views

First cohomology of the space of long knots in ℝ⁴

Let's consider the space of long knots in $\mathbb R^n$, $n>3$. I know that there are many results (Vassiliev, Turchin, Sinha, Kontsevich) about different expressions of cohomology of this space. I th …
Nikita Kalinin's user avatar
1 vote
Accepted

What is the simplest way to show that a section of a vector bundle is transverse to the zero...

It sounds like a multijet transversality theorem (see for example M. Golubitsky, V. Guillemin, Stable mappings and their singularities) in context of algebraic geometry. So, the answer is true --- a p …
Nikita Kalinin's user avatar
7 votes
4 answers
968 views

I was wondering if the set of singular loops is a (somewhere) submanifold of loop space?

The set of all smooth maps $S^1\to M^n$ ($M$ is a smooth manifold) is a generalized manifold(see http://ncatlab.org/nlab/show/smooth+loop+space). I was wondering if the set of singular loops (maps wi …
Nikita Kalinin's user avatar
5 votes
3 answers
2k views

Minimal genus, adjunction inequality

Let's consider closed simply-connected 4-manifold $M$ and some $a\in H^2(M)$. It is very natural question to estimate minimal $g$ that $a$ can be presented as embedded surface of genus $g$. As I know …
Nikita Kalinin's user avatar