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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).

5 votes

A strong annulus theorem for 3-manifolds

I think that Theorem 15.1.5 in Scott's unpublished book on three-manifolds (email him for a copy) is very close to what you want.
Sam Nead's user avatar
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3 votes

pseudo-Anosovs with given action on homology

Suppose that $f$ is a pseudo-Anosov and let $\lambda^\pm$ be its stable and unstable laminations. Suppose that $g$ is any mapping class with the following property: $g(\lambda^+) \neq \lambda^-$. Th …
Sam Nead's user avatar
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4 votes
Accepted

Does a regular neighborhood always exist for a properly embedded surface in a 3-manifold?

The answer is yes, with the correct technical hypothesis of "local flatness". (Local flatness rules out, for example, the sort of behavior shown by the Alexander horned sphere.) You are correct to th …
Sam Nead's user avatar
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0 votes

What kind of 3-manifolds arise has hypersurfaces in R^4?

You can cut a two-torus out of $\mathbb{R}^3$ and I think that a simple modification will cut a three-torus out of $\mathbb{R}^4$. So the answer to your second question is "yes".
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2 votes

Wide cylinders on half-translation surfaces

By passing to the branched double cover, branched over all singular points, it suffices to address your question for translation surfaces. (This gives up at worst a factor of two from the width.) Som …
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4 votes
Accepted

Factoring maps of handlebodies

Suppose that we are given a PL map from a handlebody $W$ to a handlebody $V$. Choose a spine for $W$. Homotope the map until the image is a regular neighborhood of the image of the spine. By genera …
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12 votes
Accepted

Finding hyperbolic metrics by approximation

To my knowledge this hasn't been done in theory (although see Harriet Moser's thesis http://www.math.columbia.edu/~moser/). But it certainly has been done in practice by Jeff Weeks' program SnapPea. …
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6 votes
Accepted

Sufficient conditions for a 3D tetrahedral complex to be homeomorphic to a 3D ball

$\newcommand{\RR}{\mathbb{R}}$The other answers are completely general, but there is simpler way if we use the (given) hypothesis that all the action is taking place in $\RR^3$. So, suppose that $T$ …
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3 votes
Accepted

Hyperbolic links

There is not enough information in your picture to give a definitive answer. If you have more details about the link $L$ then an answer will probably factor through Thurston's characterisation of hyp …
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5 votes
Accepted

Extending a 2-complex embedded in $\mathbb{S}^3$ into a simply connected one

Yes. [The tameness of $f$ makes our life much easier.] It will be convenient for the proof to assume that $C$ is pure: that is, every vertex and edge of $C$ lies in some triangle of $C$. If this is n …
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2 votes

Properly embedded annuli in genus two handlebody?

Here is another construction: Let $S$ be the once-holed torus: that is, a two-torus minus a small open disk. Then $V = S \times [0, 1]$ is homeomorphic to a genus two handlebody. [Exercise.] Let $\al …
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7 votes
Accepted

The complement of a properly embedded annulus in a handlebody is a handlebody

The answer to the question, as asked, is "no". For, suppose that $B$ is a three-ball. So, $B$ is a genus zero handlebody. Let $\alpha$ be a knotted arc properly embedded in $B$. So the fundamental g …
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3 votes
Accepted

Immersed quasi-Fuchsian surfaces surviving Dehn fillings

Notice that Hatcher proves that three-manifolds with a single torus boundary have only finitely many embedded boundary slopes. So I assume that your question one is asking about "immersed boundary sl …
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2 votes
Accepted

Is the following 3-manifold always a trivial I-bundle over a surface?

This follows, fairly easily, from the hypothesis of irreducibility and from the "annulus theorem" (see page 130 of Jaco-Shalen's book "Seifert Fibered Spaces in 3-Manifolds"). You can remove the hypo …
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7 votes
Accepted

Refining a triangulation

Suppose that $S$ is a closed, connected surface with negative Euler characteristic. Suppose that $T$ is a triangulation of $S$. Define "refine" to mean "replace each triangle by four triangles" (so t …
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