4,269 reputation
724
bio website cs.ox.ac.uk/people/…
location Oxford, United Kingdom
age 51
visits member for 4 years, 1 month
seen 2 hours ago

Oct
14
revised For a Sum-of-Squares cost functions J(x) is it true that J(x)-j* is also SOS?
a typo
Oct
14
comment For a Sum-of-Squares cost functions J(x) is it true that J(x)-j* is also SOS?
it works for a different dehomogenesation, cf. my edited answer.
Oct
14
revised For a Sum-of-Squares cost functions J(x) is it true that J(x)-j* is also SOS?
corrected the mistake in the answer
Oct
13
comment For a Sum-of-Squares cost functions J(x) is it true that J(x)-j* is also SOS?
oops, sorry, my bad. Now I recall seeing this $f^*_{SOS}=-\infty$ somewhere. Probably some other famous example is not as crazy...
Oct
13
answered For a Sum-of-Squares cost functions J(x) is it true that J(x)-j* is also SOS?
Oct
6
answered Hankel matrix commuting with a Jacobi matrix
Oct
2
comment maximizing a function involving factorial
I'd use the gamma function, which is nice and smooth, and you can use calculus on it. en.wikipedia.org/wiki/Gamma_function
Oct
1
revised Regular graphs with strongly regular edge colorings
added 188 characters in body
Oct
1
revised Regular graphs with strongly regular edge colorings
deleted 178 characters in body
Oct
1
comment Why is the spectrum of this matrix product invariant with respect to order of the multiplicants?
shouldn't $n$'s in the formula for $\sigma$ actually be $k$'s?
Oct
1
revised Regular graphs with strongly regular edge colorings
more info added
Oct
1
revised Regular graphs with strongly regular edge colorings
deleted 12 characters in body
Oct
1
answered Regular graphs with strongly regular edge colorings
Sep
30
awarded  Explainer
Sep
25
comment pencil of quadrics consisting of singular quadrics
it is essentially about pencils of matrices $A_q$, with $q(x)=x^\top A_q x$. Probably you can only find this in solution sheets to some course or textbook...
Sep
25
comment Optimization problem involving an entrywise function
and of course if you do not say anything about $\phi$ then it looks pretty hopeless,
Sep
25
comment Optimization problem involving an entrywise function
note that $X^\top\Sigma X$ need not be invertible.
Sep
24
revised Hilbert's Theorem on $L_2$ norm of polynomials in $\mathbb{Z}[X]$ - Explicit construction and a converse?
typo in the year
Sep
24
comment Conjectured integral for Catalan's constant
can you rewrite your last integral in terms of functions of a real variable?
Sep
23
comment nonnegativity conditions for a polynomial in two variables
for more variables nothing of this sort is known; Hilbert's (1893) paper substantially uses quite tricky algebraic geometry of complex plane curves (something that nowadays one would explain using en.wikipedia.org/wiki/Theta_characteristic)