bio  website  math.ubc.ca/~israel 

location  Vancouver BC  
age  64  
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Associate Professor Emeritus, University of British Columbia, and Optimization Algorithms Researcher, DWave Systems, Burnaby BC
1d

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For which $x$ the inequality $ax+be^{x/2}>c$, where $a,b,c,x>0$ and $c>2b$ holds
Already asked on MSE: math.stackexchange.com/questions/1300048/… 
1d

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Numerical equality testing
Caution: Maple's testeq can quite unreliable. For example: testeq(exp(2 * Pi * I * x)=1); $$ true$$ 
May 22 
revised 
What methods do we have to understand the spectrum of matrices with restricted entries?
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May 21 
revised 
What methods do we have to understand the spectrum of matrices with restricted entries?
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May 21 
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What methods do we have to understand the spectrum of matrices with restricted entries?
Yes, this is with entries from $\{0,1,1\}$. Since $M$ and $M^T$ have the same spectrum, it's true for columns as well. 
May 21 
answered  What methods do we have to understand the spectrum of matrices with restricted entries? 
May 21 
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Are these inequalities for primes equivalent?
There are least two cases of $p_{n+1} < a b$, namely $p_{4} = 7 < 4 \times 2$ and $p_{9} = 23 < 6 \times 4$. Of course these are not counterexamples to the OP: $p_4^2  p_3 p_5 = 6$ and $p_9^2  p_8 p_{10} = 22$. 
May 21 
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Specifying $L^p$ norms of derivatives
For a finite set of $a_n$, consider linear combinations of a finite set of basis functions and try to solve a nonlinear system of equations in the coefficients. 
May 20 
answered  Expressing a convex Polytope as a sublevel set of a function 
May 20 
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Reference for measures of commutativity needed
Trace of the commutator is always $0$, so that's not useful... If you want something that's nonzero whenever the commutator is nonzero and zero whenever the commutator is zero, a norm would seem to be the obvious choice. 
May 20 
answered  Specifying $L^p$ norms of derivatives 
May 20 
revised 
Are there examples of functions in $L_1$ and $L_\infty$ whose Fourier series divergent (“weakly”)?
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May 20 
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complexity of eigenvalue decomposition
The OP was asking about unitary matrices. Note that if $U$ is unitary and $\omega=1$ with $\omega \notin \sigma(U)$, $i (U+\omega I)(U\omega I)^{1}$ is hermitian, so solving the unitary problem is essentially like solving the hermitian problem. 
May 20 
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Are there examples of functions in $L_1$ and $L_\infty$ whose Fourier series divergent (“weakly”)?
As $x \to 0$, $\ln(1\cos(x)) \sim 2\lnx$, which is an integrable singularity. 
May 19 
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Multiple convex sets hyperplane separations
What kind of condition are you looking for? In case (2), the three convex sets $X_1$, $X_2$, $Y$ are disjoint, and so you can separate any two of them by hyperplanes. 
May 19 
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Specifying $L^p$ norms of derivatives
In the case $p=2$, integration by parts gives you $\f'\_2^2 =  \int f f'' \; dx \le \f\_2 \f''\_2$. 
May 19 
answered  Are there examples of functions in $L_1$ and $L_\infty$ whose Fourier series divergent (“weakly”)? 
May 19 
answered  How can two random variables are continuous infers that their jointly random variable is continuous 
May 17 
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Proof that image of a polynomial map is a cone
We may assume $y_3 \ne 0$. The point is that $t^2 y_3  t y_2 + y_1 = (t x_{22}  x_{21})(t x_{12}x_{11})$ has real roots, and therefore its discriminant is nonnegative. 
May 15 
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Explicit formula for the moment problem with Carleman's conditions
Carleman's is a sufficient condition for uniqueness. It is not a condition for existence. For that you need positive definiteness. 