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Timeline for Harmonic Functions

Current License: CC BY-SA 2.5

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Nov 26, 2012 at 5:30 vote accept Mykie
Jun 10, 2010 at 3:51 comment added Will Jagy Hi, Andrey. I had the feeling that such an example might be one of those axiom of choice things, but really elaborate even then. I certainly do not know how to construct it. All I can think of is constructing a non-measurable function by taking, on the real line, one representative for each equivalence class of the relation $x \sim y$ if and only if $x−y$ is rational. So wait, that trick shows that we can make a badly discontinuous example that works for all RATIONAL $\delta > 0.$ Points are equivalent if both $x$ and $y$ coordinates differ by rationals. Function constant on each class.
Jun 10, 2010 at 2:58 comment added Andrey Rekalo It would be interesting to know if there is a discontinuous function $f$ which satisfies the discrete Laplace equation at every point and for every $\delta>0$.
Jun 10, 2010 at 1:48 history edited Will Jagy CC BY-SA 2.5
my argument
Jun 10, 2010 at 1:05 history edited Will Jagy CC BY-SA 2.5
absolute value of delta
Jun 10, 2010 at 0:50 history edited Will Jagy CC BY-SA 2.5
local condition and discontinuity
Jun 9, 2010 at 21:48 vote accept Mykie
Nov 26, 2012 at 5:30
Jun 9, 2010 at 19:12 history edited Will Jagy CC BY-SA 2.5
deleted 49 characters in body
Jun 9, 2010 at 18:54 comment added Steven Gubkin It is probably to late in the year for it to be homework.
Jun 9, 2010 at 18:44 history answered Will Jagy CC BY-SA 2.5