The Stand-Up Physicist: Unifying Gravity and EM

Part of the Stand-Up Physicist series, half hour chats by Doug Sweetser about his theoretical physics research. This show touches three important puzzles: how to unify gravity and light, how to quantize such a proposal, and a new way to explain how galaxies rotate.

Category:

Science & Technology

Tags:

• Theoretical
• Physics
• Gravity
• EM
• Electromagnetism
• GEM

[CACBCCCU]

Just to clarify my thoughts about the equivalence principle, suppose something called "negative mass matter" exists, and when it is released in earth's gravity it falls upward - that means the negative mass matter has negative gravitational mass. Suppose the negative mass matter is released in zero-gravity and it stays where it is - that's what I'd call positive inertia. Both of these behaviors do not in any way seem mutually exclusive to me. Of course I could be wrong but that's my take on it.

[sweetser]

@CACBCCCU I let my equations do the speculating. As such, I have equations that predict there will be no Higgs boson. That is a dangerous prediction because it could be disproved by the LHC.

My equations also say that masses always attract each other. Anything that falls upward from the Earth could be described as repelling the Earth. Spin 1 particles can repel, spin 2 attract like particles. One would need both types of spin to see falling up and falling down.

[CACBCCCU]

Seems like someone might be looking into whether positronium has zero mass with non-zero (relativistic-type) inertia, but shielding requirements mean the environment has to be ultracold, and that's where surface effects make it hard to tell if something is massless or has mass and just likes to climb things in a typical superfluidic way. Maybe postironium would be a fast climber, maybe it wouldn't know which way to climb, seems like anyone's guess at this point.

[sweetser]

@CACBCCCU I do know people are making anti-hydrogen last longer before it gets destroyed. The aim is to see if they can observer how anti-hydrogen behaves in a gravity field. The current hypothesis is that it will behave just like hydrogen. Since this is an active area of research, we might get an answer in a few years time.

[floopsie666]

What do you mean by diffeomorphism between mass and the metric? Isn't a diffeomorphism a structure - preserving map between two manifolds or two coordinate charts?

[sweetser]

@floopsie666 Sorry if I used that exact phrase (it doesn't sound right to my ear...) Gravity does preserve the structure of a manifold. As I understand it (and it sounds like my training is less formal than yours), as one moves around the manifold, the metric changes in a smooth way. Mass is the reason for these changes.

[CACBCCCU]

Apparently some physicists at UC Davis are attempting to measure gravitational mass of positronium. Negative results may still hold a small caveat in that e.g. the number of neutrons/protons in the apparatus are not matched by an equal number of antineutrons/antiprotons, but I can't be sure the symmetry needs to be perfect, haven't thought about it enough, should've mentioned it before. Maybe a vertically-wide positronium beam could show something a narrower one wouldn't, wish I knew.

[CACBCCCU]

"Spin 1 particles can repel, spin 2 attract like particles."

To me, that's not analytical enough for the task of understanding gravity at the level of quantum gravity. EM's mutual repulsion of like-charged particles is a spin 2 effect, but it involves spin 1 quanta exchanges. So, a spin-2 attractive (gravitational) effect between two gravitationally like-charged particles requires gravitational quanta {or curved space-time} but doesn't necessarily require spin 2 gravitational quanta.

[CACBCCCU]

Looks like you've had your own experience trying to use a spin-1 particle for gravity, from what I've read on one of your recent blog entries. I'm guessing my responses to you were not persuasive, and now it seems I should add more thoughts on it, but I'm not sure that you'd see any promise in that, plus I'd be branching onto some very tentative limbs. Anyway, do let me know if you're interested in more, and thanks again.

[CACBCCCU]

I guess one last thing about the basketball analogy - in repulsion, each player only needs a grip from one side of the ball at a time, it could be a spinning half-ball, in the attraction exchange both halves of the ball are needed. Then again it's possible to take these analogies too far. Anyway, it's been an interesting exchange. Thanks.

[CACBCCCU]

I'd like to revisit the analogy of two basketball players and incorporate Thorne's spin-2 criteria, supposing there's only one ball. For a repulsive exchange one player throws and the other catches, it's not symmetrical. To get rotation symmetry, it takes 360 degrees, 180 degrees only gets one from throwing to catching. For an attraction exchange, both have to be holding onto the ball as it is passed, and they can do so in the same way 180 degrees goes from holding back to holding, it's spin-2.

[CACBCCCU]

@sweetser The rule I'd use for such negative gravitational mass is that, in the near-limit, likes attract and opposites repel, both effects being mediated by the same type of gravitational quanta. The basic model I'd use has quanta doing two phases with opposite effects, the quanta have to go about 30K ly to change phase, but source-type sets which phase is initial. The time-domain field solution for the hypothetical minimal-energy quantum is easy to describe, but it's stranger than photons.

[CACBCCCU]

Despite all the tiredness typos, I've got one more thought for tonight. Seems steady-state-field gravitons need a balance in each mass, meaning influx and outflux for each mass need to balance or else (fill in the blank anyway wanted, I don't know what, but maybe it starts with cooling) happens. Maybe not continuous balance, but short-term average. It seems to fit with the earlier idea that two like actions (in this case, one graviton in per graviton out) are needed for quantizing attraction.

[CACBCCCU]

@sweetser Oh well, I've miscorrected myself with the last try and earlier used "I've always" where "for quite a while I" fits better.

Also, I think I've read somewhere that simulating gravity using a pair of gluons in place of gravitons has has success. Another fuzzily-recalled non-attributed factiod is that any spin-2 system will act like gravity, or something like that. I guess I'm done for the day. Thanks for replying with concise points.

[CACBCCCU]

@sweetser I should have written "model that seems" not "that model that seems."

Anyway, I'm not sure if my idea of combining two spin-1 particles for a spin-2 effect is obvious, questionable, or what, but it seems straightforward to me. It reminds me of the old physics book I had with a drawing of two basketball players. Despite the way it was shown, only one needs to do something (i.e. throw the ball) for a repulsion, but both need to do the same action to produce an attractive force.

[CACBCCCU]

@sweetser I've been looking at galaxies for quite a while and in the process developed what seems to me to be a behavioural-based model for gravitational quanta, and that model that seems spin 1 to me, going by a rotational symmetry method Thorne mentions. Both ways of looking at spin are I suppose related. What Thorne called a graviton wave seems much like a pair or quadset of the sort of gravitons I had in mind. I've always seen attraction as needing a boson pair exchange, but not repulsion.