17,575 reputation
1544
bio website math.ubc.ca/~israel
location Vancouver BC
age 63
visits member for 3 years, 9 months
seen 7 hours ago
Associate Professor Emeritus, University of British Columbia, and Optimization Algorithms Researcher, D-Wave Systems, Burnaby BC

11h
comment Approximating an integral
An easy limit (definition of derivative of $(1-2\pi x\theta)^{-m}$ at $x=0$).
12h
revised Uniformly bounded operator family and pointwise convergence
added 1019 characters in body
13h
answered Uniformly bounded operator family and pointwise convergence
14h
comment Uniformly bounded operator family and pointwise convergence
By Fatou's lemma you can't have $Q_n u \to u$ pointwise a.e. if $\|u\| > 0$ and $\|Q_n\| < 1$, so the condition $\|Q_n\| \le C/n$ isn't going to work.
Dec
15
comment Approximating an integral
The singularity at $s=0$ in your integrand is a removable singularity. Therefore Igor doesn't need to consider a residue at $s=0$.
Dec
15
comment Approximating an integral
The singularity at $0$ is removable.
Dec
10
comment A problem on about a matrix norm on $\mathfrak{su}(4)$
Obviously $A=0$ might not work. The "solve for $F$" should be interpreted as "find $F$ if it exists, otherwise output 'does not exist'". But $\det(B \pm iI)$ could be $0$, e.g. $B$ could be diagonal with some entries $\pm i$.
Dec
5
answered Does very fast convergence in probability imply almost sur convergence for a continuous stochastic process?
Dec
5
comment Is the Jacobi theta function invertible?
Normally there would be no "Re" in the definition. If it's there, how do you expect to find the imaginary part of $z$?
Dec
5
comment Is the Jacobi theta function invertible?
Which Jacobi theta function? There are four of them, and they are functions of two variables. They are certainly not one-to-one.
Dec
4
answered How to convert non-PSD matrix to PSD matrix?
Dec
4
revised Upper and lower limits
added 227 characters in body
Dec
4
answered Upper and lower limits
Dec
4
answered Characteristic polynomial of Kronecker/tensor product
Dec
3
answered Analytic solution $\underset{n} {\mathrm{argmin}} \frac{a}{r + ns} + \sum_{i=0}^{n-1}\frac{b}{r + is}$
Dec
1
comment perturbation of Invariant subspaces
If $V$ is invariant under $C$, then for every $v \in V$, $Bv = v + t C v \in V$. Similarly the other way.
Dec
1
answered perturbation of Invariant subspaces
Nov
30
awarded  Enlightened
Nov
30
awarded  Nice Answer
Nov
28
comment How to test if the power of some algebraic number is the rational combination of two specific algebraic numbers?
How do you define "compute all" if there are infinitely many?