**Matti Pitkanen** (*matpitka@pcu.helsinki.fi*)

*Wed, 7 Jul 1999 10:03:43 +0300 (EET DST)*

**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Next message:**WDEshleman@aol.com: "[time 436] Re: [time 434] Re: [time 406] Dissipation"**Previous message:**WDEshleman@aol.com: "[time 434] Re: [time 406] Dissipation and quantum jumps between quantum histories"

On Wed, 7 Jul 1999 WDEshleman@aol.com wrote:

*> Time Group,
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*>
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*> This, my first post, was inspired by the discussion of "dissipation". I
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*> enjoyed reading a great many posts after being away from my computer for a
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*> time.
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*>
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*> My question is: Since Einstein tells us that all of the orbits around our
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*> Sun loose about 28 kilometers (6*pi*G*M/c^2) of orbit per orbit due to GR,
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*> then could this loss of length be interpreted as "dissipation" of orbital
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*> angular momentum.
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I am not sure what you mean with the effect the loss of

orbit... Mass point in Schwartscildt metric has stationary orbit.

If orbits are shrinking with this velocity and we assume that

Earth has orbited for at least 10^9 years one would have

that the reduction of orbit, if constant in time, would have been

about 10^11 km. This would be larger than the recent radius of

Earth's orbit! Something goes wrong!

Could you give some detail on what you mean.

In any case, all dissipative effects enter as modifications

of the basic field equations and involve parameters like coefficient

of viscosity, friction, various conductivities, etc... In General

Relativity this would mean that one adds dissipative terms into energy

momentum tensor T_ij. From my Landau-Lifcshitz I remember that in

nonrelativistic limit simplest dissipative term is something like

eta*( partial_jv_i+partial_jv_i)

for fluid. Dissipative terms are typically linear in velocity

since this is simplest term leading to the breaking of time reversal

invariance.

The covariant generalization of this term would enters to the

the energy momentum tensor and affect the geometry of spacetime

replacing it with effective 'almost envelope' for the sequence

of nondissipative spacetimes .

*>
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*> Sincerely,
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*>
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*> Bill Eshleman
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*> http://members.tripod.com.EshlemanW/
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*>
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