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1d
comment Set of Special Unitary Matrices that are dense in SU(4) and obey certain relations
$[U_1,U_n]\neq 0$ follows from $U_1 U_N U_1=U_N U_1 U_N$, as for commuting $U_1$ and $U_N$ it implies $U_1=U_N$.
1d
reviewed Approve Why do functions in complex analysis behave so well? (as opposed to functions in real analysis)
Feb
4
reviewed Reject algebraic-graph-theory tag wiki excerpt
Jan
31
comment Directed graph Laplacian with exactly one negative eigenvalue
Eigenvalues of digraphs might well be complex; e.g. there are examples where they are either complex or positive.
Jan
6
accepted embedding of $O_4^-(q)$ in $U_4(q)$
Jan
5
awarded  Quorum
Jan
3
comment embedding of $O_4^-(q)$ in $U_4(q)$
@NickGill : thanks a lot, that's exactly what I hoped for! Care to convert your comment into a proper answer?
Jan
3
revised embedding of $O_4^-(q)$ in $U_4(q)$
tex fix
Jan
3
comment embedding of $O_4^-(q)$ in $U_4(q)$
There seems to be more than one class of these, and figuring out what $H$ corresponds to looks tricky. And the value of $q\pmod 4$ seems to matter.
Jan
3
asked embedding of $O_4^-(q)$ in $U_4(q)$
Dec
24
comment Is that true all the convex optimization problems can be solved in polynomial time using interior-point algorithms
@Mehrdad : I'd also point out that "complexity" should mean "complexity of the corresponding feasibility problem". Thus e.g. the fact that every feasible solution has exponential size does not mean that the corresponding feasibility problem must be hard to solve (although it's a good indication that it might be hard...).
Dec
18
comment Is that true all the convex optimization problems can be solved in polynomial time using interior-point algorithms
@mehrdad you are right in the sense I was not careful enough. What I meant to say that there are NP- hard problems that can be formulated as convex optimisation problems. I will edit my answer to make it clear.
Dec
11
answered Which journals publish experimental results in pure maths?
Dec
11
answered Which journals publish experimental results in pure maths?
Dec
7
comment Where do I read about semi-algebraic/analytic sets?
and this: perso.univ-rennes1.fr/michel.coste/polyens/SAG.pdf
Dec
7
comment Where do I read about semi-algebraic/analytic sets?
certainly, Bochnak, Jacek; Coste, Michel; Roy, Marie-Françoise. Real Algebraic Geometry. Translated from the 1987 French original. Revised by the authors. Ergebnisse der Mathematik und ihrer Grenzgebiete (3) [Results in Mathematics and Related Areas (3)], 36. Springer-Verlag, Berlin, 1998. x+430 pp
Dec
6
comment Looking for a reference in commutative algebra
bodleian.ox.ac.uk/__data/assets/pdf_file/0019/103483/…
Dec
6
comment Looking for a reference in commutative algebra
Bodleian Library (Oxford University) will scan and email you this for £4.75. They accept Visa/Mastecard/JCB/Maestro...
Nov
30
comment Maximal induced cycles on $n$-clique graphs
Doesn't condition 3 rule out "non-adjacent cliques"?
Nov
30
comment Maximal induced cycles on $n$-clique graphs
in combinatorics people normally talk about partial linear spaces, whenever they have a subset system S on X such that any pair of points in X is in at most one subset in S. Your extra condition 3 makes S very degenerate...