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Topology of cell complexes and manifolds, classification of manifolds (e.g. smoothing, surgery), low dimensional topology (e.g. knot theory, invariants of 4-manifolds), embedding theory, combinatorial and PL topology, geometric group theory, infinite dimensional topology (e.g. Hilbert cube manifolds, theory of retracts).

4 votes

Translation distance in the curve complex

In the braid group, Ko and Lee have given a polynomial time test of reducibility using the Garside structure. (See http://arxiv.org/abs/math/0610746)
Autumn Kent's user avatar
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10 votes
Accepted

Are compact submanifolds of "S X (0,1)" with one boundary component handlebodies, where S is...

No. N could be homeomorphic to the exterior of any knot in the 3-sphere (i.e. a cube with a knotted hole).
Autumn Kent's user avatar
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7 votes
Accepted

Stallings fibration theorem

This should follow from geometrization. The fundamental group of the manifold is $\mathbb{Z}/2\mathbb{Z} \oplus \mathbb{Z}$, and geometrization should tell you that the manifold is then $\mathrm{RP}^ …
Autumn Kent's user avatar
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19 votes

Fibers of fibrations of a 3-manifold over $S^1$

As you suspect, the answer is no. There are $3$-manifolds that fiber over the circle in infinitely many ways, with fibers of unbounded genera. Thurston constructed a seminorm on $H_2(M,\partial M; \ …
Autumn Kent's user avatar
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4 votes

Teichmuller theory and moduli of Riemann surfaces

I think a good example is Kerckhoff's solution to the Nielsen Realization Problem, which asks if every finite subgroup of the mapping class group is realized as a group of isometries of some hyperboli …
Autumn Kent's user avatar
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3 votes

Normal subgroups of fuchsian groups

This doesn't say much about the elliptic case, but there is Hempel's theorem that the normal closure of an element $\alpha$ contains a (power of a) simple curve $\beta$ if and only $\alpha$ is a (powe …
Autumn Kent's user avatar
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17 votes
Accepted

Homology generated by lifts of simple curves

As far as I know, this is open. In fact, I think the following weaker question is open. Let $\Theta$ be the set of loops $\gamma$ in $\widetilde \Sigma$ such that the image of $\gamma$ in $\Sigma$ …
Autumn Kent's user avatar
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10 votes

Higher homotopy groups of slice disk complement

To add to Ryan's answer, $2$--knots usually don't have aspherical complements, see Dyer & Vasquez, The sphericity of higher dimensional knots, Canad. J. Math. 25(1973), 1132-1136. This suggests a com …
Autumn Kent's user avatar
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6 votes

Why should I care about Heegaard-Floer theory?

Kronheimer, Mrowka, Ozsváth, and Szabó obtained a new proof of Gordon and Luecke's Knot Complement Theorem using monopole Floer homology. That's pretty good, I think. They also proved that $\mathbb{ …
12 votes
Accepted

Topological rigidity of compact manifolds in dimension three

Yes. When the manifolds are Haken this is a theorem of Waldhausen. See Ian Agol's answer here. Since your manifolds are aspherical, they are irreducible by the Poincaré conjecture. Since they have …
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7 votes

Degrees of self-maps of aspherical manifolds

For $K(\pi, 1)$'s, the answer is: Because Euler characteristic is multiplicative under covering spaces. Edit: As pointed out in the comments, I was assuming the map was $\pi_1$--injective. Here' …
Autumn Kent's user avatar
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29 votes

Fundamental group of 3-manifold with boundary

No. The Baumslag--Solitar groups $\langle a, b | ab^m a^{-1} = b^n \rangle$ are not three-manifold groups when $m \neq n$. See: Heil, Wolfgang H. Some finitely presented non-$3$-manifold groups. Proc …
Autumn Kent's user avatar
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15 votes
Accepted

Word problem for fundamental group of submanifolds of the 4-sphere

Update: My memory was quite blurry about this when I originally answered. See Gonzáles-Acuña, Gordon, Simon, ``Unsolvable problems about higher-dimensional knots and related groups,'' L’Enseigneme …
Autumn Kent's user avatar
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10 votes
Accepted

Seifert surfaces of torus knots

There's the usual description of the Seifert surface for a general cable obtained by taking copies of a Seifert surface for the knot and a fiber for the cable in the solid torus. See Ken Baker's disc …
Autumn Kent's user avatar
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4 votes

A problem/conjecture related to 4-manifolds that deserves a name. What name does it deserve?

In dimension 3, you have the sphere theorem, the torus theorem, the annulus theorem, and the disk theorem (which is the loop theorem and Dehn's lemma put together). So, if you didn't require the sphe …
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