All Questions
22 questions
3
votes
2
answers
247
views
Morse approximation with bounded number of critical points
Let $(M^3,g)$ be a compact Riemannian 3-manifold and let $f\in C^{\infty}(M)$ be a smooth function. Does there exist a constant $k>0$ (possibly depending on $M$ and $g$) such that $f$ can be $C^2$-...
- 716
5
votes
1
answer
708
views
Morse theory for manifolds with boundary
I need a reference to some basic facts about Morse theory on manifolds with boundary.
Namely, if a critical point lies on the boundary, then the gradient of function might be nonzero and it brings ...
- 45k
15
votes
1
answer
2k
views
Good introduction to Morse-Novikov theory?
Morse theory investigates the topology of compact manifolds using critical points of real-valued functions $f\colon\, M\to \mathbb{R}$. Motivated by problems in dynamical systems, Novikov (Multivalued ...
- 26.3k
4
votes
0
answers
421
views
What are your common strategies/remedies when your new theory/idea stuck in most cases?
Sorry if this is not a suitable post for MO.
Sometimes after reading the origin of a theory/idea in differential topology I put myself in the shoes of that mathematician and ask myself, Did you do the ...
- 4,195
59
votes
3
answers
5k
views
Operations via Morse Theory
I am interested in seeing if and how Morse Theory can "do everything". Some core things are handle decomposition, Bott periodicity, and Euler characteristic. But what do the normal (co)...
- 4,713
1
vote
0
answers
194
views
Existence of Morse function on suspension
Let $X$ be a smooth simply connected compact manifold of dimension $n$ with boundary. Let $Y$ be a smooth compact manifold of dimension $n+1$ without boundary such that $H_{i+1}(Y)=H_{i}(X)$(reduced ...
- 61
8
votes
1
answer
176
views
Analog of Cerf theory in PL
Is there an analog of Cerf theory in PL?
More specifically, given two handle decompositions of a PL (relative) cobordism $W$, is it always possible to go from one handle decomposition to the other via ...
- 44.4k
6
votes
0
answers
177
views
Equivariant Morse theory for non-compact Lie groups
Let $G$ be a Lie group acting properly on a smooth manifold $M$. The (non-equivariant) definition of a Morse function does not carry over to equivariant functions $M \rightarrow \mathbb{R}$ (where $\...
- 63.9k
2
votes
0
answers
88
views
$1$-parameter analytic functions are almost everywhere Morse
Let $I = [t_{0}, t_{1}]$ be a closed interval with $t_{0} < t_{1}$ and let $M$ be a compact real analytic $n$-dimensional manifold without boundary. Furthermore, let $f:I \times M \rightarrow \...
- 21
3
votes
0
answers
130
views
A generalization to Bott‘s theorem (from Milnor’s “Morse theory”)
This is Theorem 22.1 of Milnor‘s Morse theory:
Let $M$ be a complete Riemannian manifold, let $p,q\in M$ be so that the space $\Omega’$ of minimal geodesics joining $p$ to $q$ is a topological ...
- 1,630
40
votes
3
answers
3k
views
Height function on 2-torus with only 3 critical points
It is well-known that a Morse function on $T^2$ has at least $4$ critical points, but also that there exist functions $f\colon T^2\to\mathbb R$ with only 3 critical points (the least possible number ...
- 18.4k
0
votes
0
answers
64
views
Dense set of functions on manifold with no local optima
Given a smooth manifold $M$ and another $S$, consider a smooth function $\psi: S \times M \rightarrow \mathbb{R}$, and use this to define $\psi_s:M\rightarrow \mathbb{R}$ by $\phi_s(p):= \psi(s,p)$.
...
- 2,099
11
votes
1
answer
562
views
Relation between Morse Theory and integration against Euler Characteristic
I'm studying Robert Ghrist papers on integration against Euler Characteristic. I am particularly interested in the relation with Morse Theory. I am trying to understand the proof of Theorem 25.1 (page ...
- 27.5k
25
votes
1
answer
4k
views
Can the constant rank theorem for smooth manifolds be generalized to nonconstant rank?
The constant rank theorem says that
if $f\colon M→N$ is a smooth map whose rank equals some fixed $k≥0$ at any point of $M$, then, locally with respect to $M$ and $N$, the map $f$ assumes the easiest ...
- 26.3k
6
votes
2
answers
817
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 ...
- 12.8k
9
votes
0
answers
248
views
Parametrized cancelations in stable Morse theory
Let $B$ be a closed manifold. Let $\pi : M\to B$ be a submersion such that each fiber is a manifold without boundary. Let $f : M \to \mathbb{R}$ be a function such that the restrictions $f_x$ to each ...
- 356
3
votes
1
answer
497
views
Perturb a given smooth function to a Morse function relative to fixed level sets, which are already fine
This question was not answered on math.stackexchange.
Let $M$ be a manifold (not necessarily compact) , for the sake of clearness embedded in $\mathbb{R^n}$ and $f\colon M\rightarrow \mathbb{R}$ a ...
CommunityBot
- 1
4
votes
1
answer
399
views
Construction of appropriate Morse functions
I am interested in the properties of connectedness of level sets of Morse functions. Let $M$ a compact smooth $n$-manifold, and $1\leq k<n$. Is it possible to construct $k$ Morse functions $f_1,\...
- 19.4k
6
votes
1
answer
221
views
cell decomposition of real homogeneous hypersurfaces
Let $f(x_1,\ldots,x_n)\in\mathbf{R}[x_1,\ldots,x_n]$ be a homogeneous polynomial
and consider the real hypersurface $H=\{(x_1,\ldots,x_n)\in\mathbf{R}^n:f(x_1,\ldots,x_n)=1\}$. Assume to simplify ...
CommunityBot
- 1
6
votes
1
answer
864
views
Is the space of gradient-like vector fields contractible?
Let $M$ be a compact manifold (without boundary) and let $f:M\to \mathbb{R}$ be a fixed Morse-function.
Question: Is the space $GVect(M,f)$ of all gradient-like vector-fields for $f$ contractible ...
- 281
3
votes
1
answer
380
views
Special Morse function on a Riemann surface
Let $f: S \to \Bbb R$ be a Morse function on a Riemann surface. Let $x_0$ be a saddle point of $f$. Since $x_0$ is a critical point of $f$, it makes sense to talk about the bilinear forms $f_{z\...
- 34.7k
2
votes
3
answers
2k
views
Index of a Morse function via the Hessian tensor
For a smooth function $f:M\to \mathbb{R}$ one usually defines the degeneracy and index of a critical point $p\in M$ in terms of the eigenvalues of the Hessian matrix $(\partial^2 f/\partial ...
- 27.5k