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Re: dielectric constant



Ludwik Kowalski wrote:

... the absence
of clear statements in textbooks. For example, something
like this: " the wavelength dependence of n for glass or
water can be very accurately calculated in QED."

I got 500 hits when I tried
http://www.google.com/search?q=glass+dielectric-constant+ab-initio

Water is probably problematic, because of all the long-range
correlations due to hydrogen-bonding.

Metals and semiconductors also have long-range electron-
electron correlations. The dielectric constant can be
calculated, but it requires a supercomputer plus theoretical
techniques that aren't going to be found in undergraduate
textbooks anytime soon.

The line shape, I suppose, depends on parameters of two
levels. How can this be translated into the frequency
dependence of n or K?

You mean when there are more than two levels?
Isn't that covered by the summation-symbol in Feynman
volume I equation 31.20?