149,055 reputation
595247
bio website math.ubc.ca/~israel
location Richmond, Canada
age
visits member for 3 years, 10 months
seen 6 hours ago

I'm an Emeritus Associate Professor of Mathematics at University of British Columbia and an Optimization Algorithms Researcher at D-Wave Systems in Burnaby BC


6h
answered Contour Integration where Contour contains singularity
6h
answered If $X + X^T$ is positive definite, is $X^{-1} + X^{-T}$ also positive definite?
6h
comment about a sequence of isometries' convergency.
The $x_m$ could all be the same. If you just need the convergence to be pointwise rather than uniform, you can take them all to be the same.
7h
answered Rank of block matrix
12h
answered Given a square matrix where $a_{11}=c\neq 0$ and $a_{ij}=0$ otherwise, can we find a matrix B such that B and A+B have no common eigenvalues?
12h
comment Find the $n$ for which $σ(n) = 15$
When you eliminate all other possibilities, the one remaining is unique.
12h
comment Find the $n$ for which $σ(n) = 15$
@Sasha you mean $\sigma(n) \ge n + 1$.
12h
answered about a sequence of isometries' convergency.
15h
answered existence of a borel probability measure on $[0,1]$ such that $\int f d\mu=\lim_{k\to\infty}\frac {1} {N_k} \sum_{i=1}^{N_k}f(x_i)$ given sequence
16h
comment 'Rational' solutions of sine
$2 \sin(\pi r) = -i \exp(i\pi r) + i \exp(-i \pi r)$. $\pm i$ and $\exp(\pm i \pi r)$ are algebraic integers, being roots of unity. The sum or product of algebraic integers is an algebraic integer.
16h
answered 'Rational' solutions of sine
16h
answered Solve the following matrix equation $X'X=A$
18h
awarded  Enlightened
18h
awarded  Nice Answer
19h
answered weak -star topology on ball M[0,1]
20h
awarded  Enlightened
22h
answered Matching Algorithm in Graph Theory
22h
revised Solve for matrix that is hidden inside a scalar
added 167 characters in body
22h
comment Solve for matrix that is hidden inside a scalar
Sorry, typo: I'll edit.
22h
comment Eigenspaces and jordan normal form
That's the point. Once you have $A$ diagonalized, you have its eigenspaces (corresponding to blocks of indices where $D$ has each eigenvalue of $A$ as diagonal element); $TBT^{-1}$ consists of blocks on the diagonal corresponding to these, and you put each of these into Jordan form.