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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”.

8 votes
0 answers
463 views

Self diffeomorphism of $S^2\times S^2$

The main question is motivated from the answer of this question https://math.stackexchange.com/questions/2481200/finite-groups-gs-which-acts-freely-on-s2-times-s2 Is it true that every self diffeomo …
Anubhav Mukherjee's user avatar
2 votes
1 answer
1k views

Is it true that given any two point in $M$ if there exists an unique geodesic joining those ... [closed]

This following doubt initially came to my mind while thinking the relationship between number of genus of a manifold and number of geodesic between given two points. DOUBT: Suppose $M\subset \mathbb{ …
Anubhav Mukherjee's user avatar
17 votes
3 answers
938 views

Can an oriented closed $n(\geq 2)$-dimensional manifold be smoothly embedded in $\mathbb{R}^...

Can anyone provide me with an example of an orientable closed manifold $M$ of dimension $n\geq 2$, which cannot be smoothly embedded in $\mathbb R^{2n-1}$? I know these cannot exist for $n=1$, i.e. $S …
Anubhav Mukherjee's user avatar
30 votes
2 answers
2k views

Does there exist any non-contractible manifold with fixed point property?

Does there exist any non-trivial space (i.e not deformation retract onto a point) in $\mathbb R^n$ such that any continuous map from the space onto itself has a fixed point. I highly suspect that the …
Anubhav Mukherjee's user avatar
11 votes
0 answers
334 views

Isotopy on embedded 3-manifolds in 4-manifolds

Suppose that $X$ be an oriented, closed four-manifold. Suppose that $Y$ is an oriented, closed three-manifold smoothly embedded in $X$. Suppose also that $f:X \to X$ is a diffeomorphism that fixes $Y …
Anubhav Mukherjee's user avatar
6 votes
2 answers
810 views

Can a Morse function define a unique structure on a closed manifold?

I was thinking about the doubt that if $M$ and $N$ are closed manifold and if there exists two Morse function $f$ and $g$ respectively on $M$ and $N$ with the following property that they both have sa …
Anubhav Mukherjee's user avatar
13 votes
2 answers
925 views

Example of two exotic closed 4-manifolds s.t. SW(X)=0

I am interested in seeing examples of two closed 4-manifolds $X_1,X_2$ such that $SW(X_i)=0$ and they are homeomorphic but not diffeomorphic. So far in the literature I've only found examples which s …
Anubhav Mukherjee's user avatar
4 votes
2 answers
405 views

Can we convert any non-vanishing vector field into geodesic field by changing metric?

If $M$ is a smooth closed manifold together with a non-vanishing (maybe unit) vector field $X$. In what condition can we construct a Riemannian metric on $M$ s.t $X$ be the geodesic field of on $TM$?
Anubhav Mukherjee's user avatar
25 votes
1 answer
1k views

What can we say about the Cartesian product of a manifold with its exotic copy?

Let $M$ be a smooth oriented manifold, and let $M^E$ be an exotic copy, i.e homeomorphic but not diffeomorphic to $M$. Is it true that $M\times M$ is diffeomorphic to $M\times M^E$? I am intere …
Anubhav Mukherjee's user avatar
14 votes
0 answers
310 views

When can we extend a diffeomorphism from a surface to its neighborhood as identity?

Let $M$ be a closed and simply-connected 4-manifold and let $f: M^4 \to M^4$ be a diffeomorphism such that $f^*: H^*(M;\mathbb{Z})\to H^*(M;\mathbb{Z})$ is the identity map. Moreover, let $\Sigma \sub …
Anubhav Mukherjee's user avatar
8 votes
2 answers
778 views

Does there exist a Haken manifold where all its incompressible surfaces are non-separating?

Every non-zero element in $H_2(M,\mathbb Z)$ corresponds to an incompressible surface. So these surfaces are non-separating. But I'm interested in knowing about separating incompressible surfaces. A r …
Anubhav Mukherjee's user avatar