bio | website | dm.unipi.it/~martelli |
---|---|---|
location | Pisa (Italy) | |
age | 42 | |
visits | member for | 5 years, 3 months |
seen | 1 hour ago | |
stats | profile views | 3,504 |
Associate professor in geometry (Pisa, Italy)
Aug
21 |
comment |
Gluing two diffeomorphisms and then smoothing
Yes, it can, because you can pick two collars of the boundaries, and isotope each diffeomorphism $\phi^\pm$ so that it acts productwise on each collar. This is also the same technique one uses to prove that two smooth isotopies can be composed and transformed into a smooth isotopy. |
May
20 |
awarded | Yearling |
Apr
13 |
awarded | Nice Question |
Apr
7 |
awarded | Popular Question |
Feb
5 |
awarded | Good Answer |
Jan
23 |
comment |
Fox re-imbedding theorem in dimension four
More generally, which re-imbedding techniques do we know? If I have a 3-manifold in S^4, how can I modify its embedding so that it is not isotopic to the previous one? |
Dec
9 |
revised |
Does there always exist a sequence of handle moves between handle decompositions that does not increase index? (+ ref. request)
added 3 characters in body |
Dec
9 |
revised |
Does there always exist a sequence of handle moves between handle decompositions that does not increase index? (+ ref. request)
fix |
Dec
9 |
answered | Does there always exist a sequence of handle moves between handle decompositions that does not increase index? (+ ref. request) |
Dec
3 |
comment |
Can knot diagrams be monotonically simplified using under moves?
As suggested by Marco, this knot can be fully simplified via level moves, see zanellati.it/knot/Satellite_knot.pdf I just got this information from the author of the program who is following this page, so drawings of more complicated unknots are welcome :-) It would be interesting to try one more additional doubling as suggested by Joel... |
Nov
28 |
awarded | Nice Answer |
Nov
24 |
answered | Additivity of simplicial volume |
Nov
4 |
comment |
Examples of Einstein four-manifolds of negative sectional curvature
using Dehn filling on cusped hyperbolic manifolds (see the papers of Anderson and Bamler) you can construct plenty of manifolds that admit both Einstein and non-positive sectional curvature metrics, but not simultaneously as far as I understand. |
Nov
4 |
comment |
Can knot diagrams be monotonically simplified using under moves?
I don't know (I still haven't seen the program running), but if you perform the diagram connected sum I suppose it simplifies the knot exactly as before. One should try some hard version of the trefoil knot... |
Nov
4 |
revised |
Can knot diagrams be monotonically simplified using under moves?
picture |
Nov
4 |
answered | Can knot diagrams be monotonically simplified using under moves? |
Oct
10 |
awarded | Good Answer |
Sep
30 |
awarded | Explainer |
Aug
28 |
awarded | Popular Question |
Aug
25 |
comment |
Is a generic closed orientable hyperbolic 3-manifold Haken?
are we sure that any configuration of tetrahedra appears with probability one? This does not hold for graphs (some graphs almost never appear as subgraphs of a random 4-valent graph). |