Timeline for Negative Gravity and Spacetime: Does this align with known physics or is it inherently flawed?
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| Jun 13, 2021 at 15:53 | comment | added | user110866 | Let us continue this discussion in chat. | |
| Jun 13, 2021 at 2:36 | comment | added | user110866 | Clearly therefore negative mass-energy particles create a host of issues which are not compatible with current physical laws. Of course such a particle may be possible, but a lot of additional physically laws would have to be created to describe this particle. For instance there would be additional symmetries to explain why this particle appears in some places but not spontaneously everywhere. Also how this particle would interact thermodynamically is ill defined for the reasons I mentioned. This is not at all compatible with known physics as the OP asks. (5) | |
| Jun 13, 2021 at 2:31 | comment | added | user110866 | This particle would not require any energy expenditure to create since its energy is already negative. It therefore could appear anywhere at any time since its existence spontaneously breaks time translation symmetry! Additionally if this hypothetical particle had negative mass-energy than thermodynamic equilibrium (TE) would not be meaningful with the existence of this particle. Since TE involves interactions which tend towards the lowest energy configuration, these interactions would tend towards accelerating this particle since increasing momentum would contribute to a lower energy (4) | |
| Jun 13, 2021 at 2:17 | comment | added | user110866 | @elduderino For another way of discussing this topic is approach from the perspective of time translation symmetry in particle interactions as thermal equilibrium is approached. Of course recent work has shown time translation symmetry can be spontaneously broken for non-equilibrium system (time crystals), however this certainly does not imply that the symmetry is broken for the interactions which compose the system. Consider the physics therefore of particle which has a net negative energy in its ground state. (3) | |
| Jun 13, 2021 at 1:49 | comment | added | user110866 | @elduderino The dispersion relation in turn requires the mass (even negative mass) contribute a positive value to the total energy of a particle. The only mathematically consistent way is to have imaginary mass, but what does this mean physically? This is also precisely why I avoided too much discussion of the Cosmological constant which is not compatible with current QFT and is currently an open question in physics. (2) | |
| Jun 13, 2021 at 1:41 | comment | added | user110866 | @elduderino Yes, I was trying to keep my post accessible. Certainly the conservation of energy is about net energy exchange. But specifically the issue of dark energy producing negative gravity centers around the $T^{00}$ component of the Stress-Energy Tensor. This term is dependent on relativistic mass. However, the conservation of energy requires the dispersion relation (assuming mass-energy equivalence which is at the crux of general relativity and which also arises naturally in the Dirac formulation of QM). (1) | |
| Jun 12, 2021 at 15:46 | comment | added | el duderino | (cont) Finally, I'm pretty sure you can have negative mass/energy densities if we're talking about $T^{00}$ as our definition. For instance, the cosmological constant term $\Lambda g_{\alpha \beta}$ in the EFE looks exactly like the stress energy tensor for a perfect fluid with negative mass density $\rho = -\Lambda$ when taken in a comoving, inertial frame. All that being said, it's been a while since I studied GR so if you're able to address these points with more precise language it's definitely possible I'm wrong or misinterpreting you. | |
| Jun 12, 2021 at 15:38 | comment | added | el duderino | (cont) Also, total energy is a difficult concept to define in GR-- the local statement of energy conservation $\nabla_{\alpha}T^{\alpha \beta} = 0$ relies on the connection and thus choice of coordinates, so you have to be pretty careful what you're talking about when talking about conservation of energy in GR. The usual quantities we use often aren't globally conserved for this reason, and when you can find energy-like quantities that are globally conserved they're much less intuitive than your definition as the ability to move objects through space. | |
| Jun 12, 2021 at 15:35 | comment | added | el duderino | Can you elaborate a bit on the math behind your claim that negative energy density violates conservation of energy/the geodesic equation? The argument you gave in the edit seems a bit vague and like you could twist it around to also say that positive energy densities violate conservation of energy because they add energy to the system, which clearly isn't true-- the point of conservation of energy is that the total energy has to be constant, not that it's zero. | |
| Jun 11, 2021 at 22:02 | history | edited | user110866 | CC BY-SA 4.0 |
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| Jun 11, 2021 at 21:37 | history | edited | user110866 | CC BY-SA 4.0 |
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| Jun 11, 2021 at 21:30 | history | answered | user110866 | CC BY-SA 4.0 |