Robert Israel

86,404 reputation

52135

bio	website	math.ubc.ca/~israel
	location	Richmond, Canada
	age
visits	member for	2 years, 2 months
	seen	13 mins ago
stats	profile views	8,674

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

	86,404 reputation	bio	website	math.ubc.ca/~israel	visits	member for	2 years, 2 months
52135 badges		location	Richmond, Canada		seen	13 mins ago

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May 6	answered	To solve a differential equation
May 6	answered	roots of the polynomial equations and relation among the coefficients
May 6	comment	Dividing and multiplying surds - Rule It's not true if $x$ and $y$ are negative.
May 5	comment	Every exposed point is a extreme point Your definition of exposed point is not quite right. You want $H$ to be a supporting hyperplane, not just any hyperplane.
May 5	revised	Showing that the inverse of the perturbation of a compact operator by a bounded operator remains compact. added 87 characters in body
May 5	answered	linear functional-equation $ \,2f\left(x+1\right)=f\left(x\right)+f\left(2x\right) $
May 5	comment	linear functional-equation $ \,2f\left(x+1\right)=f\left(x\right)+f\left(2x\right) $ But "all functions $R \to R$" says that it doesn't have to be continuous.
May 5	comment	Showing that the inverse of the perturbation of a compact operator by a bounded operator remains compact. In this setting, $L^{-1}$ bounded does not imply $L$ bounded: $L$ is not defined on all of $H$ but only on a subspace.
May 5	revised	Showing that the inverse of the perturbation of a compact operator by a bounded operator remains compact. added 92 characters in body
May 5	answered	Showing that the inverse of the perturbation of a compact operator by a bounded operator remains compact.
May 5	answered	What is the image of the strip $0\le\Re(z)\le2$ under $z\mapsto\dfrac{1}{z}?$
May 5	comment	Notation for number of value changes in a sequence $\delta_{ij}$ is the Kronecker delta, which is $1$ if $i=j$ and $0$ otherwise.
May 4	awarded	Enlightened
May 4	awarded	Nice Answer
May 4	awarded	statistics
May 3	answered	Notation for number of value changes in a sequence
May 3	comment	If $f$ is entire and $g$ has an essential singularity, must $f\circ g$ have an essential singularity? ... namely the Casorati-Weierstrass theorem. Also you need that $f$ has dense range, which is a corollary of Liouville's theorem.
May 3	revised	I roll 6-sided dice until the sum exceeds 50. What is the expected value of the final roll? added 572 characters in body
May 3	answered	I roll 6-sided dice until the sum exceeds 50. What is the expected value of the final roll?
May 3	comment	Find all functions $f$ that assign a real number $f(x)$ to every real number $x$ . . . No, $f(x) = a x + b$ is always a solution.