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Jan 22 |
revised |
How to flip one triangulation on a surface into another
Softened the language in the opening of the question. Being blunt is rude! |
Jan 21 |
comment |
How to flip one triangulation on a surface into another
Igor - there are proofs that use the hyperbolic geometry. You could perhaps invoke some property of shear coordinates, or you could flip towards the convex hull of light-like vectors in the hyperboloid model, or some related thing. But I don't see how you can just say "Delaunay" and be done??? |
Jan 21 |
revised |
How to flip one triangulation on a surface into another
reply to the update |
Jan 21 |
comment |
How to flip one triangulation on a surface into another
Igor - this doesn't work... The second, non-geometric, triangulation will not be embedded. Generically its triangles will have bodies with positive area and then three long zero-area legs that follow geodesic paths in the singular flat metric. Thus the "angles" you rely on will generically be zero. |
Jan 20 |
revised |
How to flip one triangulation on a surface into another
Hatcher |
Jan 20 |
answered | How to flip one triangulation on a surface into another |
Jan 18 |
comment |
Is there a faithful transitive locally finite action of the modular group?
What does "orbits under each $g$" mean? Do you mean that for all $n \in \mathbb{Z}$ and for all $g$ the set $\{g^k \cdot n \mid k \in \mathbb{Z}\}$ is finite? Is there some reason why you require $G$ to act on $\mathbb{Z}$? Or would you be happy with an action on any countable set? |
Jan 18 |
answered | How many knots are there with hyperbolic volume less than a given constant |
Jan 16 |
reviewed | Approve question on Stieltjes-Lebesgue Measure |
Jan 11 |
reviewed | Approve Dropping three bodies |
Jan 11 |
revised |
Teaching the fundamental group via everyday examples
Added two more examples, edited the transitional material for clarity. |
Dec 27 |
revised |
Knots in 3-manifolds
Simplified a lot. |
Dec 27 |
revised |
Knots in 3-manifolds
Simplified a lot. |
Dec 27 |
comment |
Knots in 3-manifolds
Regarding typesetting: \pi gives $\pi$ when surrounded by dollar signs. |
Dec 27 |
answered | Knots in 3-manifolds |
Dec 27 |
reviewed | Approve Best Algebraic Geometry text book? (other than Hartshorne) |
Dec 23 |
comment |
Growth of the number of generators in hyperbolic groups
The existence of hyperbolic HNN extensions (eg some free-by-cyclic groups) makes this tricky. Does it help to assume that the hyperbolic group has trivial abelianization? |
Dec 21 |
awarded | Necromancer |
Dec 21 |
comment |
Do geodesics in SL2R map to geodesics in the hyperbolic plane?
Can ballistic curves be reparameterized to become geodesics? (Perhaps allowing variable speed?) |
Dec 21 |
comment |
Do geodesics in SL2R map to geodesics in the hyperbolic plane?
Geodesics that point in the direction of the SO(2) subgroup cannot map to geodesics. I believe that these map to the constant path. If so, do you allow the constant path as a geodesic? |