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Mathematics professor at Cambridge

Oct
26
comment Believing the Conjectures
As for Maximize, I find it unhelpful in this context, since it is not clear what is "likely to occur". For example, it is still open whether there exists an infinite-dimensional Banach space such that every operator defined on it is a multiple of the identity plus a nuclear operator. I feel as though the answer could go either way, and no principle like Maximize is going to alter that perception. On the other hand, the existence of examples with comparable properties, such as Argyros and Haydon's construction where "nuclear" is replaced by "compact", does have an impact.
Oct
26
comment Believing the Conjectures
The fact that there ought to be a separable example is too trivial to count as a success of Reflection, since if there is any example at all, you can take a separable subspace of it and then you've got a separable example.
Oct
25
answered Believing the Conjectures
Oct
20
awarded  Yearling
Oct
14
revised “Mathematics talk” for five year olds
changed "phenomenon" to "phenomena".
Sep
20
awarded  Nice Question
Sep
8
revised Philosophy behind Mochizuki's work on the ABC conjecture
fixed typo
Sep
8
comment Is every distance-regular graph vertex-transitive?
Yes, but the hypercubes are vertex transitive, as are most of the obvious families.
Sep
7
answered Is every distance-regular graph vertex-transitive?
Sep
6
comment A combination of two well-known complexity problems
@joro, what you're asking is in a sense what's in the back of my mind when I asked the original question: hard instances of graph isomorphism are rather delicate, so can they be combined with a condition about containing Hamilton cycles? If they can't, then the answer to my question is that you can indeed distinguish between the two situations.
Sep
6
comment A combination of two well-known complexity problems
@Suvrit, if you were to take two typical hard instances for the Hamilton cycle problem, one that contains a Hamilton cycle and one that doesn't, then it is very likely that it will be easy to tell that they are non-isomorphic. (For example, their degree sequences are likely to differ.) In the other direction, if you have two graphs of large minimal degree that are a difficult case for graph isomorphism, they will both contain Hamilton cycles. I'm not sure whether this is answering your question though.
Sep
6
comment A combination of two well-known complexity problems
@Gerhard "I'm sure it's the latter" Paseman, it's only half the latter. I know what zero-knowledge proofs are, but don't immediately see how they answer the question. Could you spell it out?
Sep
6
comment A combination of two well-known complexity problems
@Richard Stanley -- that's why I insist that they are both hard, though obviously if graph isomorphism is hard then so are NP-complete problems so I could have just said "assuming that graph isomorphism is hard".
Sep
5
comment A combination of two well-known complexity problems
A quick remark: one can of course ask the same question for many other NP-complete problems -- I'd be just as interested, for example, in the same question but with "clique of size m" instead of "Hamilton cycle".
Sep
5
asked A combination of two well-known complexity problems
Jul
31
awarded  Stellar Question
Jul
24
awarded  Popular Question
Jun
18
awarded  Good Question
Jun
18
awarded  Good Question
Jun
18
awarded  Good Question