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bio website cs.ox.ac.uk/people/…
location Oxford, United Kingdom
age 51
visits member for 4 years, 2 months
seen 26 mins ago

14h
comment Irreducibility of a polynomial
oops, sorry, voted to reopen.
16h
comment Can all unit-distance graphs have their vertices at algebraic integers?
@Ilya: ah, right. And not only into a 6-wheel, but any subgraph of the hexagonal lattice. I wonder if this is the complete answer.
17h
comment Can all unit-distance graphs have their vertices at algebraic integers?
@Ilya: good point. This means that $G$'s with a homomorphisms to 6-cycle is a good class, in terms of the original question. (No idea why such graphs are interesting though) :-)
18h
revised Largest eigenvalue adjacency matrix-link deletion
typo fixed
21h
comment Can all unit-distance graphs have their vertices at algebraic integers?
How about adding a bit of intuition, say do you know such $f$ for the triangle? (and if yes, then one immediately has $f$ for the 3-colourable graphs).
1d
comment When can the group of permutations generated by the translations of a group be identical with the group of all permutations on this group?
en.wikipedia.org/wiki/Cayley%27s_theorem ?
1d
revised Can every finite abelian $p$-group with duality pairing be written as cokernel of a symmetric matrix over the $p$-adic integers?
edited title
2d
comment Can a graph be reconstructed from its cycle lengths?
It seems that if you know this sequence and the adjacency matrix of the graph, then you can compute the matching polynomial, which is #P-complete.
Jan
23
comment Open access journals in number theory
IMHO a publication of a close to final version on arxiv.org is good enough for all practical purposes.
Jan
23
comment accelerate convex optimization by proximal projection
can't you just stop your quadratic optimisations early?
Jan
23
comment research on the structure/properties of permutation matrix/table with $(i,j)th$ entry as $\pi_j\circ \pi_i^{-1}$
it's not clear what kind of order on permutations you are talking about, and, indeed, what the entries of these tables are.
Jan
18
comment When is edge colored circulant isomorphism polynomial?
@joro - sure, they use the definition I mentioned, too.
Jan
18
comment When is edge colored circulant isomorphism polynomial?
In your reduction attempt, you lose the needed automorphisms, so it does not work.
Jan
18
comment When is edge colored circulant isomorphism polynomial?
Edge-coloured circulant graphs are edge-coloured graphs admitting a cyclic transitive automorphism group. Colouring here is just a map from a set of colours to the edges.
Jan
18
reviewed Approve Saito-Wright definition of Rickart C*-algebras
Jan
18
comment Minimally intersecting subsets of fixed size
to generalise my example to another small $k$, take a the affine space of bigger dimension; in more generality, you can play with putting together different 2-designs with appropriate parameters.
Jan
18
comment Minimally intersecting subsets of fixed size
generalising for arbitrary $k$ is hard, as optimal codes are in general not known.
Jan
16
comment Minimally intersecting subsets of fixed size
@Bill - I added a possible construction to my answer.
Jan
16
revised Minimally intersecting subsets of fixed size
answering a question from the comment
Jan
16
comment Does anyone know this determinant?
So you have a complete graph with edges weighted in Hankel matrix-like fashion, and then you take the "unsigned Laplacian" matrix of this (weighted) graph. Hmm...