2,470 reputation
723
bio website metis.ms.unimelb.edu.au/…
location Melbourne, Australia
age 32
visits member for 2 years, 7 months
seen May 25 at 4:48

I am a low dimensional topologist.


May
22
reviewed Approve Is g( ) rational if it looks that way on a large rational subset?
May
19
reviewed Approve When the Lovász theta-function saturates its upper bound
May
18
awarded  Deputy
May
14
reviewed Reviewed Why do people use “formal calculation” to describe informal calculations?
May
11
reviewed Approve Does the following type of Gronwall inequality hold?
May
6
comment Kleinian groups containing an isomorphic copy of itself
@DannyNguyen I don't understand your comment and I would be grateful if you could help me clear up my misunderstandings. First, you have dropped the condition that the subgroup be proper, which seems essential to the definition of co-Hopfian. Second, I don't follow why "is" is in bold in your correction.
May
3
comment Remainder is always a multiple of 9
Emmanuel, you might consider reading up on casting out 9's (en.wikipedia.org/wiki/Casting_out_nines). Reducing a number mod 9 can be determined by summing it's digits. Since reversing the digits preserves this sum, your observation fits nicely into this pattern. However, it is more general: for instance 29, 38, 47, 56, 65, 74, 83, 92 all are 2 mod 9 so you can take the difference of any pair of these numbers and it will be 0 mod 9.
May
3
reviewed Approve Vanishing of $\hat{A}$ genus and positive scalar curvature
Apr
30
reviewed Reviewed how wiggly is a generic level set?
Apr
30
reviewed Reviewed Irreducibles in polynomial rings
Apr
29
comment 3-manifolds with isomorphic fundamental groups
Thanks Henry. Isn't assumed throughout your paper that you guys discuss only oriented 3-manifolds? I was really hoping to find a reference that deals with the non-orientable case as well. I fully understand why one would like to avoid the pathologies of non-orientable manifolds especially when considering virtual properties. However, I wondering if anyone has a nice approach to 3-manifolds with the same fundamental group regardless of orientablity.
Apr
29
comment 3-manifolds with isomorphic fundamental groups
I think you might want to be a little careful citing Scott. He also requires that the manifolds are closed, right? There are examples of non-homomorphic Seifert fibered spaces over the disk with two exceptional fibers that are non-homeomorphic. D^2(3,1)(3,1) and D^2(3,1)(3,2) form a pair of these type of examples. One can see they are not homeomorphic by performing surgery along the peripheral curve that bounds an annulus, which results in L(3,1)#L(3,1) and L(3,1)#L(3,2).
Apr
29
asked 3-manifolds with isomorphic fundamental groups
Apr
29
reviewed No Action Needed Self adjoint operator and vertex conditions in quantum graphs
Apr
29
reviewed Reviewed Dyer-Lashof operations and the homology of GL_n
Apr
27
reviewed Approve ideals of polynomial ring with complex number coefficients
Apr
23
comment Limit Group decomposition
I am also having trouble understanding what you are asking. Here is a discussion that might help you refine your question: berstein.wordpress.com/2011/04/27/…. It has a number of references that might be helpful.
Apr
20
revised Descriptive Complexity of Knot Equivalence
added "complete" to line 3.
Apr
20
answered Descriptive Complexity of Knot Equivalence
Apr
17
awarded  Custodian