16,774 reputation
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bio website math.ubc.ca/~israel
location Vancouver BC
age 63
visits member for 3 years, 7 months
seen 5 hours ago
Associate Professor Emeritus, University of British Columbia, and Optimization Algorithms Researcher, D-Wave Systems, Burnaby BC

5h
answered Finite series with reciprocal factorials
10h
answered How to solve $e^{f(x)} + a f(x) + bx = 0$
1d
answered lower bound of a trace quadratic form
2d
awarded  Nice Answer
2d
comment How did the summation operation come into use?
From en.wikipedia.org/wiki/Gnomon : "Hero of Alexandria defined a gnomon as that which, when added to an entity (number or shape), makes a new entity similar to the starting entity. In this sense Theon of Smyrna used it to describe a number which added to a polygonal number produces the next one of the same type."
2d
comment Obscure Names in Mathematics
The Tomato Can principle.
2d
revised Obscure Names in Mathematics
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2d
answered Obscure Names in Mathematics
Oct
22
answered How did the summation operation come into use?
Oct
20
comment Quantitative stability: Hausdorff distance between subdifferentials
You can easily modify this example to come up with smooth $f$ and $g$ with $\|f - g\|_\infty$ but $\delta f(0) = \{C\}$ and $\delta g(0) = \{-C\}$, $f$ and $g$ being translates of smoothed versions of $C |x|$.
Oct
20
answered Convergence on a random graph
Oct
20
answered The limit of edge-midpoint convex polyhedra
Oct
19
revised A generalisation of Narayana-like numbers (walks on the 2D lattice)
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Oct
19
revised A generalisation of Narayana-like numbers (walks on the 2D lattice)
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Oct
19
revised A generalisation of Narayana-like numbers (walks on the 2D lattice)
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Oct
19
revised Unbounded convex not containing a ray - example without using a basis
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Oct
19
answered Unbounded convex not containing a ray - example without using a basis
Oct
15
answered Does the Gamma function preserve integers?
Oct
15
revised Points with pairwise integer distances in the plane
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Oct
15
answered Points with pairwise integer distances in the plane