Just a holding post for 3 related links, so I can draw others attention to it:
SciAm article : Dark Energy Tested on a Tabletop
Sabine Hossenfelder’s earlier “BackReaction” response to the original source paper.
Rick Ryals speculation on consequences for the cosmological constant and the standard model (from Sabine’s Facebook timeline):
Negative mass particles would fall “up”… should have negative density and negative pressure…
A cosmological constant with negative pressure *mimics* negative mass via its anti-gravitational effect, and a cosmological constant that is a less dense form of the same mass energy as ordinary matter rho<0 would have real massive particle potential when enough of it was gravitationally condensed to attain the matter density… until then the “almost material” would logically be “dark”.
It would also be virtually undetectable, except gravitationally, and in a finite model matter generation from the vacuum structure *causes* expansion via the hole that the “hole” leaves in the vacuum during matter generation which necessarily increases negative pressure via rarefaction of the ever thinning vacuum structure.
This coincidence makes me wonder if anyone has ever written down the basis of wave functions in this background, including an expansion of the field in corresponding creation and annihilation operators… computed the stress-energy tensor in that background and quantitatively described the vacua. Has anyone worked out the matrix elements of the stress-energy tensor between Einstein’s original finite vacuum and the one-particle states?
Has anyone even checked with GR to see if negative mass has negative pressure?
Anyone else share that wonder?
[Post Notes : Since the response trail has gone cold on Sabine’s FB thread, I’m bringing forward here for future follow-up, Ricks additional inputs. It’s a worry that serious open-minded physicists can address these details beyond the initial rebuttal:
Ian : “We know there’s no explanation for the cosmological-constant problem within general relativity and the Standard Model of particle physics,” so, maybe suspend belief in the standard model for a moment, and I’d be interested in your response to Rick Ryals speculation?
Rick : Thanks but it isn’t exactly speculation as it all falls naturally from the mentioned cosmological model. In General Relativity’s most natural universe, the vacuum has negative density when,
In this static state, pressure is proportional to -rho, but pressure is negative in an expanding universe, and so energy density is positive.
The vacuum energy density is less than the matter energy density, but it is still positive, so positive matter density can be obtained locally if you condense energy from this negative pressure vacuum into a finite region of space, until the energy density over this region equals that of the matter density. This will, in-turn, cause negative pressure to increase, via the rarefaction of Einstein’s vacuum energy, (as the vacuum pulls back), so this expanding universe does not run-away, because the increase in positive mass-energy is offset by the increase in negative pressure that results when you make particles from Einstein’s negative pressure vacuum.
In Einstein’s static model, G=0 when there is no matter. The cosmological constant came about because we do have matter, so in order to get rho>0 out of Einstein’s matter-less model you have to condense the matter density from the existing structure, and in doing so the pressure of the vacuum necessarily becomes less than zero, P<0.
Sabine : [via twitter, (max 140 chars)]
Yes, negative (gravitational) mass has a negative pressure.
No, it doesn’t explain accelerated expansion.
Rick : Yes it does when a greater volume of the vacuum is required each time that you make a particle pair due to the rarefying effect that matter generation has on the finite vacuum.
But the universe is held flat and stable as acceleration increases …. until said process insidiously compromises the integrity of the structure and boom… the footprint of this universe gets laid down with the matter field for physicists of the next universe to scratch their collective heads about for all eternity… or so it would appear …
Rick and I continued some private chat on the implications, but these are not worth sharing until serious physicists take the physics inputs seriously. Anyone?]
[Continuing with chat response from Sabine (Matter corrected to Energy in the header):
[So, to the original question] I said, “Yes, negative gravitational mass can have a negative gravitational pressure to the same extent that positive gravitational mass can. That is to say, IF it’s pressureless, then of course it wont.
[T]he rest of the comment, I don’t know what [Rick] means.
[He asked] “Has somebody considered that the cc is a field and quantized it?”
Yes, sure. You can’t quantize a constant. And the cc doesn’t have ‘holes’ because it’s, well, constant.
From my lay perspective two obvious conditional assumptions there:
One, “if” gravitational mass (positive or negative) is pressureless.
Two, “whether” the cosmological constant is (literally) a constant. It’s that very assumption that is being questioned of course. Why it has the particular value it does in the current observable universe? The same point being questioned by Unger and Smolin, the dogma that such laws and constants are fixed and not evolving in the histories of universes.]