22,180 reputation
592167
bio website math.rice.edu/~andyp
location Houston, TX
age 35
visits member for 5 years, 8 months
seen 15 mins ago
associate professor at Rice University

Jun
19
comment Homotopy type of a CW complex
Yes, see Corollary A.12 of Hatcher's book.
Jun
18
comment What would you do if you improve your own result that is submitted but not publishied?
@GerryMyerson: This being the internet, we can be certain that whatever the distribution is, the mean level of trustworthiness is vanishingly small.
Jun
17
comment What would you do if you improve your own result that is submitted but not publishied?
This is a complicated and slightly delicate question. You should ask mentors who know your situation well (e.g. your advisor if you are still a student) rather than trust random people on the internet.
Jun
10
comment Should we post on arXiv only papers in publishable shape (or very close)?
The only way to repair your reputation is by doing good research. A few strong papers would certainly make quite a bit of difference. You should also talk to your mentors about this. They can give you advice that is far more tailored to your situation than that coming from some strangers on the internet.
Jun
9
comment Should we post on arXiv only papers in publishable shape (or very close)?
If you are a youngish person, you should never post papers to the arXiv that are not in publishable shape. People will judge you very negatively. Sometimes senior people whose reputations are secure do this for various reasons, but you don't want a poorly written/incomplete paper to form one of the earliest impressions of you that the community makes.
Jun
3
answered Realizing braid group by homeomorphisms
Jun
1
comment Introductory article of knot Heegaard Floer Homology
This it totally on-topic, so you should not feel bad at all for posting it. It's a great and useful answer!
May
30
comment Exact sequences of pointed sets - two definitions
I fail to see what this has to do with the question.
May
30
comment Is there a (satisfying) proof that cellular cohomology is isomorphic to simplicial cohomology that doesn't use relative cohomlogy?
That's not what it asked for. It asks specifically for alternate proofs of the equivalence between singular and cellular cohomology. That is a very focused question, and you make no attempt to answer it.
May
26
awarded  Good Answer
May
26
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@JosephO'Rourke: Thanks for the compliment! My writing backlog is embarrassingly long right now, but I'll think about think about turning this into a brief paper at some point.
May
25
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@JosephO'Rourke: By the way, here's one way to think about the conditions. The "local" condition ensures that we can find a surface with boundary $A$ (either an annulus or a Mobius band) containing $\gamma$ such that $\gamma$ is a geodesic on $A$. The remaining conditions ensure that $A$ can be extended to a sphere. Those conditions are not needed when the set $U$ I define is not dense since in that case there is freedom in choosing $A$, so we can choose it to extend to a sphere.
May
25
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@JosephO'Rourke : I just edited the answer to include a summary. I give necessary and sufficient conditions for the sphere to exist. These conditions are not necessarily satisfied when $\gamma''$ never vanishes.
May
25
revised Is every closed curve in 3D a geodesic on a genus-0 surface?
added 1927 characters in body
May
23
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
This "answer" (by John Robertson, now converted to a comment by a moderator) doesn't really have any mathematical content, and in any case is wrong. Every unknotted simple closed curve in $\mathbb{R}^3$ lies on the surface of a smooth ball, but my answer identifies a series of obstructions that prevent you from making it a geodesic.
May
23
awarded  Nice Answer
May
23
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@JosephO'Rourke: Thanks for posting this lovely problem, by the way! Solving it was a fun way of procrastinating on some very boring administrative work...
May
23
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@IgorRivin: In my edit, I explain briefly why this is not a problem.
May
23
comment Is every closed curve in 3D a geodesic on a genus-0 surface?
@DavidSpeyer: Good point! I was very tired and thought I had an argument for this, but I was wrong. And in fact there are even more obstructions even if it is an annulus. I deleted the comment and edited things to discuss the new obstructions.
May
23
revised Is every closed curve in 3D a geodesic on a genus-0 surface?
added 2431 characters in body