Robert Israel
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Registered User
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Associate Professor Emeritus, University of British Columbia, and Optimization Algorithms Researcher, D-Wave Systems, Burnaby BC
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May 3 |
revised |
Extension of power bounded operators over a finite subspace added 1 characters in body |
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May 2 |
accepted | Extension of power bounded operators over a finite subspace |
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May 2 |
revised |
Extension of power bounded operators over a finite subspace added 590 characters in body |
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May 2 |
answered | Extension of power bounded operators over a finite subspace |
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May 1 |
accepted | An Interesting variant of Rayleigh Quotient |
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Apr 30 |
awarded | ● Scholar |
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Apr 29 |
accepted | On solution of a recursion with rectangular matrices |
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Apr 26 |
awarded | ● Student |
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Apr 25 |
asked | A regular polytope |
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Apr 25 |
answered | What is the effect of adding 1/2 to a continued fraction? |
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Apr 25 |
comment |
What is the effect of adding 1/2 to a continued fraction? See also Knuth, "The Art of Computer Programming", vol. 2, sec. 4.5.3 ex. 14. |
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Apr 23 |
answered | An Interesting variant of Rayleigh Quotient |
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Apr 21 |
answered | On solution of a recursion with rectangular matrices |
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Apr 19 |
awarded | ● Nice Answer |
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Apr 8 |
comment |
Distance between poisson points in two disjoint unit discs Integrate over $x \in D_1$ the area of the intersection of $D_2$ with the disk of radius $r$ about $x$. I doubt that you'll end up with a closed-form expression. |
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Apr 6 |
accepted | Is there an analog of determinant for linear operators in infinite dimensions as that of finite dimensions? |
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Apr 6 |
answered | Fitting algebraic expression to a number [algorithm] |
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Apr 5 |
accepted | Methods for solving two variable recurrence |
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Apr 4 |
answered | Distance between poisson points in two disjoint unit discs |
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Apr 4 |
answered | Is there an analog of determinant for linear operators in infinite dimensions as that of finite dimensions? |
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Apr 3 |
answered | Methods for solving two variable recurrence |
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Apr 3 |
comment |
Does this matrix shape have a name? @SSra: I don't think you heard about them from me. I don't recall ever writing (or reading) "Bose-Mesner" before. |
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Mar 31 |
comment |
Does this matrix shape have a name? Looking at en.wikipedia.org/wiki/Bose%E2%80%93Mesner_algebra it appears that Bose-Mesner matrices are somewhat more general: I think you have the case $n=2$. |
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Mar 31 |
comment |
Does this matrix shape have a name? By the way, for this $n \times n$ matrix to be non-singular you also need $a + (n-1)b \ne 0$. |
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Mar 31 |
comment |
Iterates converging to a continuous map But that counterexample is not the iterates of some $\varphi$. |
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Mar 30 |
answered | easter problem - egg shapes |
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Mar 25 |
comment |
Bounding the second derivative of the log-determinant By "positive" you mean "positive definite"? |
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Mar 24 |
accepted | is there any algebraic function that has a specific relation to transcendental one? |
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Mar 24 |
answered | is there any algebraic function that has a specific relation to transcendental one? |
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Mar 22 |
answered | eigenvalues of two nonnegative matrices |
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Mar 22 |
revised |
Possible to find a set of log-concave functions with log-concave sums? added 156 characters in body |
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Mar 22 |
answered | Possible to find a set of log-concave functions with log-concave sums? |
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Mar 22 |
revised |
Software to numerically solve partial differential equation added 1 characters in body |
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Mar 22 |
answered | Software to numerically solve partial differential equation |
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Mar 21 |
answered | “Wild” solutions of the heat equation: how to graph them? |
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Mar 21 |
comment |
“Wild” solutions of the heat equation: how to graph them? That should be $x^{2n}$, not $x^2$. |
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Mar 20 |
awarded | ● Good Answer |
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Mar 19 |
accepted | TSP, but for all routes not all points |
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Mar 19 |
comment |
Solid angles of a tetrahedron In a triangle with two equal angles, the sides opposite these are equal. This is because of symmetry. But a tetrahedron with two equal solid angles need not have any symmetry. |
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Mar 18 |
accepted | When are two operators simultaneously diagonalisable? |
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Mar 17 |
answered | When are two operators simultaneously diagonalisable? |
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Mar 17 |
answered | TSP, but for all routes not all points |
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Mar 15 |
comment |
Mean minimum distance for N random points on a unit square (plane) I asked Maple to evaluate your quadruple integral numerically. This uses the NAG procedure DCUHRE (TOMS algorithm 698). With the default settings it was unable to obtain the desired accuracy, but with relative error tolerance epsilon $= 10^{-4}$ the result was $.5214059909$. |
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Mar 14 |
awarded | ● Yearling |
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Mar 13 |
comment |
Why to count integers that are relatively prime to their euler function? In general, mathematicians count things because that's what they do. No deeper reason is really required. The fact that in this case there is a connection to group theory, as well as to Carmichael numbers, is a bonus. |
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Mar 12 |
comment |
Why to count integers that are relatively prime to their euler function? See also oeis.org/A003277 and references there. |
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Mar 11 |
comment |
Expectation of $(c+e^{N(0,\sigma^2)})^{-n},\, n>0$ Another possibility is to use Laplace's method, expanding around the maximum of the integrand $\dfrac{(c+e^x)^{-n}}{\sqrt{2\pi} \sigma} e^{-x^2/(2 \sigma^2)}$, which is at the real root of $(n \sigma^2 + x) e^x + c x$. |
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Mar 7 |
revised |
modulo of sums of consective powers added 17 characters in body |
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Mar 6 |
revised |
modulo of sums of consective powers edited body; added 58 characters in body |
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Mar 6 |
comment |
modulo of sums of consective powers Yes, thanks. I'll edit. |
