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Re: plot dirac delta function? [message #49521 is a reply to message #49406]

Sat, 29 July 2006 22:17

swingnut
Messages: 30
Registered: September 2005

Member

Ah, I see we're about to head off into the realm of defining functions,
ever a popular discussion (not the least of which is because I relish
the opportunity to learn more about it, not being a mathematician). Why
do you say this? In plasma kinetic theory a while back, the prof give
us the pop quiz about the value of particle distributions made from
sums of delta functions. As with the "How do you put an elephant into
the refrigerator?" test, everyone jumped to the wrong answer since the
integral of the Dirac delta is 1. The function wasn't a sum of
integrals, its a sum of deltas, so the value of the distribution at a
particle's parameters in the phase space we were working in is
infinity.

Looking at a Dirac delta as the limit of a sequence of Guassians as the
width of the guassian goes to zero with the constraint that the
integral of the Dirac goes to one also provides the value of infinity,
because that's the only way an integral could possibly be non-zero when
its upper and lower bounds are the same.

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[Message index]

		plot dirac delta function? By: Nic on Wed, 19 July 2006 03:30
		Re: plot dirac delta function? By: James Kuyper on Sun, 23 July 2006 19:07
		Re: plot dirac delta function? By: swingnut on Sat, 29 July 2006 22:27
		Re: plot dirac delta function? By: swingnut on Sat, 29 July 2006 22:17
		Re: plot dirac delta function? By: James Kuyper on Sun, 30 July 2006 07:32
		Re: plot dirac delta function? By: Carsten Lechte on Fri, 11 August 2006 14:18
		Re: plot dirac delta function? By: James Kuyper on Sun, 30 July 2006 07:18
		Re: plot dirac delta function? By: James Kuyper on Fri, 11 August 2006 15:35
		Re: plot dirac delta function? By: priorbee on Fri, 25 November 2016 02:13

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