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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?