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Re: Imaginary reality



At 01:59 PM 4/23/00 -0500, Jack Uretsky wrote:
What is "the heat bath" that you refer to?

Generally speaking, the term "heat bath" is a reasonably well-established
shorthand that refers to whatever degrees of freedom receive the energy
that is dissipated.
-- Specifically, in the RLC case, it refers to the internal degrees of
freedom of the resistor, the heatsink to which it is bolted, the sky into
which it radiates, and whatever other modes are linked in by convection et
cetera.
-- Similar remarks to the absorbing optical medium that we
discussed: heat bath = internal degrees of freedom + linked environmental
modes.

Are you talking about the
effect of ohmic heating on the resistor (in the RLC case)?

Sort of, with the following caveats:

1) The effect of dissipation is not necessarily a significant increase in
temperature. (Imagine a very, very large heat sink.) Different nitpickers
will have differing opinions as to whether this energy-dissipation should
be called "heating" or not.

2) There is
a) an effect "from" from the macroscopic electrical degree of freedom
"to" the heat bath (namely dissipation), and
b) an effect in the other direction (namely, thermal fluctuations).

Fact: you can't have one without the other; this is called the
fluctuation-dissipation theorem.

Item (a) is reasonably well described by including a real part in the
reactance (or an imaginary part in the index of refraction) but item (b) is
not.

3) If anybody needs help appreciating the importance of item (b), please
re-read "Ratchet and Pawl" (_The Feynman Lectures on Physics_ volume I
chapter 46).