Re: infinite moments
From: Ian Jermyn (Ian.Jermyn_at_sophia.inria.fr)
Date: 07/21/04
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Date: Wed, 21 Jul 2004 17:38:31 +0200
I don't think anyone is in any doubt that it can have pragmatic
applications. I do not believe there is a well-defined question, but
whatever it is, it is not that.
Ian.
-- -------------------------------------------------- Ian Jermyn INRIA (Ariana) 2004 route des Lucioles B. P. 93 06902 Sophia Antipolis Cedex France T: +33 (0)4 9238 7683 F: +33 (0)4 9238 7643 E: Ian.Jermyn@sophia.inria.fr W: http://www-sop.inria.fr/ariana/personnel/Ian.Jermyn "Richard Ulrich" <Rich.Ulrich@comcast.net> a écrit dans le message de news:3c1tf09juviahnlbmpt0shtngnlr61qd9i@4ax.com... > On Wed, 21 Jul 2004 10:19:36 +0200, "Ian Jermyn" > <Ian.Jermyn@sophia.inria.fr> wrote: > > > Did I say 'finite quantities' implied 'finite mean'? One can always > > construct infinities by using bad co-ordinates, as you do in the example of > > the angle and its tangent. If one uses bad co-ordinates, one has to be > > careful how they are interpreted. In any case, co-ordinates have no physical > > significance in themselves. How will you measure this infinite quantity? > > > > In addition to the above, there is the objection that you raise yourself, > > that the system you describe does not exist. In a real physical system there > > will be all sorts of other factors, including, in some limit, quantum > > mechanics, that will prevent your analysis from being correct. > > Is the question is whether the Cauchy distribution, with undefined > mean and infinite variance, has pragmatic applications? > > Funny you should mention quantum mechanics. > > I quote myself, quoting in a post in 2000: > - From Philip Bevington's book "Data Reduction...", > (page 49, 1969 edition) concerning the Lorentzian > (Cauchy) distribution, "which occurs quite often > in nuclear physics data reduction." > > "It is an appropriate distribution for describing data > corresponding to resonance behavior, such as the > variation with energy of the cross section of a nuclear > reaction or the variation with velocity of absorption > of radiation in the Mossbauer effect." > > > > -- > Rich Ulrich, wpilib@pitt.edu > http://www.pitt.edu/~wpilib/index.html
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