bio | website | cs.ox.ac.uk/people/… |
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location | Oxford, United Kingdom | |
age | 50 | |
visits | member for | 3 years, 11 months |
seen | 9 hours ago | |
stats | profile views | 1,809 |
Aug 30 |
revised |
On the positivity of matrices
added 204 characters in body |
Aug 30 |
comment |
On the positivity of matrices
IIRC, the minimal size for counterexample is $n=5$. |
Aug 30 |
comment |
On the positivity of matrices
This computational technique is called semi-definite programming. |
Aug 30 |
answered | On the positivity of matrices |
Aug 30 |
reviewed | Approve suggested edit on Is there an analog of the Barratt-Eccles construction for group-like E_∞-spaces and E_∞-ring spaces? |
Aug 25 |
reviewed | Approve suggested edit on Largest eigenvalue adjacency matrix-link deletion |
Aug 25 |
answered | Largest eigenvalue adjacency matrix-link deletion |
Aug 25 |
comment |
Invariant planes of a nilpotent matrix with two Jordan blocks of size two
The 2-dimensional subspaces are parametrised by the points on a quadric $Q$ in $P^5$, via Plucker coordinates. You can write down how $N$ acts there, and take the fixed vectors of linear map which satisfy the quadratic relation defining $Q$. Thus you will have them parametrised by the intersection of $Q$ and the linear subspace of fixed points. |
Aug 24 |
answered | Real solutions for systems of monomial equations |
Aug 24 |
comment |
Real solutions for systems of monomial equations
this is a particular case of a problem involving binomial ideals; the latter are quite well-studied, in the context of toric varieties. |
Aug 18 |
comment |
How to prove a Proposition of Rouquier?
how can it be so that some statements in the text indicate that it's not clear how to prove some other statement in the same text?! |
Aug 18 |
comment |
What is the minimal girth of a cayley graph for Alt(n) in which the girth relator is not a proper power?
6? Why? Why not 42? :) |
Aug 18 |
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What is the minimal girth of a cayley graph for Alt(n) in which the girth relator is not a proper power?
from topology point of view, you might want to disregard length 2 loops. |
Aug 18 |
reviewed | Approve suggested edit on Kaplansky's idempotent conjecture for Thompson's group F |
Aug 13 |
comment |
Linkage between homotopy equivalence and identification of algorithms
this is called "univalent foundations of mathematics", see e.g. homotopytypetheory.org |
Aug 8 |
answered | Possible degrees of faithful projective representations of $\mathrm{PSL}(k,q)$ and $\mathrm{Sp}(2k,q)$ over complex numbers |
Aug 8 |
comment |
Possible degrees of faithful projective representations of $\mathrm{PSL}(k,q)$ and $\mathrm{Sp}(2k,q)$ over complex numbers
The poster most probably doesn't have access to Magma. (well, the same computations can be done in GAP (gap-system.org), which is free...) |
Aug 6 |
comment |
When polynomial GI implies polynomial (edge) colored GI?
other questions are harder :) |
Aug 6 |
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When polynomial GI implies polynomial (edge) colored GI?
the explicit generators are trivial to find. Indeed, the action on the degree 2 vertices is just the action of $S_n$ on pairs {[12],[13],..,[pq]...}, for p<q. |
Aug 6 |
comment |
When polynomial GI implies polynomial (edge) colored GI?
Actually if you read details in A052565 you'll see that it is n! for n>3. |