X-Message-Number: 22022
From: 
Date: Wed, 18 Jun 2003 16:35:10 EDT
Subject: Re: CryoNet #22016 Infrared divergence

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From: "michaelprice" <>:

> 
> When a charge is accelerated the low-frequency energy of the 
> Bremsstrahlung radiation emitted is independent of frequency,
> so that the number of low energy photons emitted scales with the
> inverse of the frequency.  Total photon number is obtained by
> integration of the inverse function to yield the logarithmic function.
> Since log(0) = infinity we have an infinite number of low-energy 
> or "soft" photons, even though the total energy emitted is finite.
> 
I disagree :-(
The real acceleration takes place in a finite time T,  Photons with period 

(inverse of the frequency) far larger than T can't be radiated away. they remain
as virtual photons. So, the number of photons, real + virtual is indeed 

infinite, but the number of real ones is finite. The infinite photon problem is 
an 
artifact coming from using a classical idea (instantaneous photon production) 
in a quantum problem.

Yvan Bozzonetti.


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