Although I didn’t realize it at the time, the answer that I got was out of context with the finite model that I was studying:

Aaron Denny answered that:
In GR gravitation is essentially curvature due to the energy contained in a region. Pair-production changes this energy from photons to the mass of other particle pairs, but the energy amount, and thus the curvature and gravitation should be the same.

http://www.lns.cornell.edu/spr/2003-08/msg0053209.html

Domenic asked:
Or are you also looking at the gravitational influence of having an infinite number of negative-energy fermions at every point in space?

Particle theory says that for every fermion type there is another
fermion type that has exactly the same mass, and therefore no priori
distinction between matter and anti-matter. I incorrectly concluded that the opposite value of all other charges (quantum numbers), indicates that the asymmetry between the two classes of particles is due to the fact that the anti-particle has -rho and negative mass until it becomes a real particle.

http://www.lns.cornell.edu/spr/2003-11/msg0056253.html

I latter figured out with the help of Nathan Urban that the antiparticle actually has negative pressure when the model is not static because the vacuum only has negative density when P=-u=-rho*c^2. In this static state, pressure is proportional to -rho, but pressure is negative in an expanding universe, and so energy density is positive, e.g., vacuum energy density is less than the matter energy density, but it is still positive.

Someone better than me needs to write down the basis of wave functions in this background, including an expansion of the field in corresponding creation and annihilation operators. Then compute the stress-energy tensor in that background and quantitatively describe the vacua. Then work out the matrix elements of the stress-energy tensor between the vacuum and the one-particle states.

Anybody wanna start a retro-revolution?…

“The balls it your court…”

Just remember to be home by midnight!

And, I don’t see any connection between your talk of the Dirac sea and your talk of gravitational effects on pair creation. Pair creation is generally viewed as creating particles and antiparticles; presumably when you work out the gravitational effects on such, you are doing so in the particle-antiparticle paradigm, and not in the Dirac sea paradigm. Or are you also looking at the gravitational influence of having an infinite number of negative-energy fermions at every point in space? If so, I missed that…

http://www.astro.ucla.edu/~wright/cosmo_constant.html

Which is supported by that region of pseudo-negative pressure density that gets produced by the Casimir effect, which is the closest known real representative for a real object that expresses the characteristics of the, (also pseudo), negative mass object that falls quite naturally from Dirac’s negative energy solutions.

http://www.lns.cornell.edu/spr/2006-03/msg0073465.html

Best of luck to her.

That’s very interesting, Tony. You’re a mine of historical quotes! Just for the record here, let me point out the similarities (noted originally by Tony) between Segal’s ideas and Riofrio’s Machian no-DE cosmology. Island, from this Machian perspective one can view the classical spacetime as an emergent phenomenon with no /\, which is possible because the /\ is associated with levels of quantumness [multiple levels is a post-QFT notion of an hbar (N) heirarchy, including Dark Matter - see Pitkanen's work, for instance] and for a large range of hbar, /\ can be replaced by a variable speed of light. Einstein’s intuition then works only as an effective description, relying on the ficticious vacuum of a single-level hbar QFT.

Oh, and I don’t know that John wasn’t receptive, he simply didn’t reply, and may have never even read what I wrote, so let’s not lay this on him. I have put this before many others who can take responsibilty for that, and I’m already mad at John for “other”, (read anthropic), forms of willful ignorace, so I don’t need to add this to his list…

The 10-parameter Poincare group ( 3 spatial rotations, 3 boosts (timelike rotations), and 3 translations ) does not allow compression of spacetime. To get compressions (and preserve light-cone structure) you need to add 5 more transformations (1 dilation and 4 special conformal transformations) which gives you the Conformal Group Spin(2,4) = SU(2,2) that acts non-linearly on 4-dim spacetime.

That gives you a conformal picture of gravity on the cosmological scale, as was investigated by Irving Ezra Segal. It can be shown ( see gr-qc/9809061 by R. Aldrovandi and J. G. Peireira ) that combining the 4 special conformal transformations with the 6 Lorentz transformations you get what looks like a /\ cosmological “constant” (since it can vary, it is really more like what is now called “Dark Energy”).
Further, you can by a modified MacDowell-Mansouri mechanism use the conformal group to get an Einstein-Hilbert Lagrangian with cosmological “constant”,
so
it seems to me clear that the basic picture of island is not only realistic, but can be directly connected with more conventional formulations of gravity, and that people who “… dismiss …[island's]… point out of hand …” are more to be pitied for their ignorance than paid attention to.

Also, island said;
“… particle creation from vacuum energy … you have to condense the matter density from the zero pressure metric … this physics predicts something like a higgs mechanism, but no higgs boson …”.

This is in line with the idea of the Higgs as a Tquark condensate ( see for example hep-ph/0311165 by Hashimoto, Tanabashi, and Yamawaki ), since a Higgs condensate of particle-antiparticle pairs from the vacuum would naturally be dominated by the heaviest component, that of the heaviest quark-antiquark pair, the Tquark.
So,
again it seems to me clear that the basic picture of island is realistic (the Higg being, not an independent fundamental particle, but a result of a Tquark condensate). Further, island’s picture can be described in conventional physics terms (as in the paper cited above).

Tony Smith

PS – As to why John Baez might not have been receptive to the above interpretation (of the conformal group a la I. E. Segal), Segal was advisor for Baez’s 1986 MIT Ph.D., and (in an obituary for Segal in the Notices of the AMS 46 (June/July 1999) 659-668, Baez said:
“… In his later years Segal spent most of his time on … the … cosmology …[of]… conformal geometry … it never seemed right to me … I tried to get him to explain … His explanation did not convince me. Later I tried to explain what I thought was his error. He became quite angry … this was very difficult, and our relationship became strained … I eventually wound up avoiding him …”.