CPT symmetry and antimatter gravity in general relativity

[kodama]

CPT symmetry and antimatter gravity in general relativity
M. Villata

Published 28 March 2011 • Europhysics Letters Association
EPL (Europhysics Letters), Volume 94, Number 2
Abstract
The gravitational behavior of antimatter is still unknown. While we may be confident that antimatter is self-attractive, the interaction between matter and antimatter might be either attractive or repulsive. We investigate this issue on theoretical grounds. Starting from the CPT invariance of physical laws, we transform matter into antimatter in the equations of both electrodynamics and gravitation. In the former case, the result is the well-known change of sign of the electric charge. In the latter, we find that the gravitational interaction between matter and antimatter is a mutual repulsion, i.e. antigravity appears as a prediction of general relativity when CPT is applied. This result supports cosmological models attempting to explain the Universe accelerated expansion in terms of a matter-antimatter repulsive interaction.is this well motivated and plausible? what would be the implications if the above theory is correct?
how would this impact SM, SUSY, GUT string theory, LQG etc if the above is correct.
one prediction is that antimatter would fall up around matter, which can be verified by experiment

there would be no necessary reason to have a SM baryogenesis, since there could be entire galaxies made of anti-matter equal in amount to matter, but repelled by it. dark energy could also be explained as repulsion of galaxies that are equally matter and antimatter. a spin-2 quantum field which gives a graviton is always attractive, never repulsive. so if the above theory is correct, it would seem to imply QG theories based on a spin-2 field are incorrect.

the no hair theorem may be violated and a black hole made from a star that collapsed of antimatter may repel a black hole of a collapsed matter star.

 

[mfb]

99% of the mass of everyday objects comes from QCD binding energy which is neither matter nor antimatter. If you want to fit them into that scheme, you would have to assign them to 50% matter and 50% antimatter or something like that. Either way, if this 99% part would not contribute, or cancel, different elements (with a different fraction of mass coming from binding energy) would feel different accelerations, an effect that would have been noted long ago.

There is no direct test of antibaryons falling down yet, but having them falling up is a really exotic approach that needs a lot of explanations why the equivalence principle works so well.

 

[kodama]

99% of the mass of everyday objects comes from QCD binding energy which is neither matter nor antimatter. If you want to fit them into that scheme, you would have to assign them to 50% matter and 50% antimatter or something like that. Either way, if this 99% part would not contribute, or cancel, different elements (with a different fraction of mass coming from binding energy) would feel different accelerations, an effect that would have been noted long ago.

There is no direct test of antibaryons falling down yet, but having them falling up is a really exotic approach that needs a lot of explanations why the equivalence principle works so well.

if gr is extended with cpt, does the conclusion follow?

 

[mfb]

Which conclusion?

Gravity should be locally CPT invariant, globally the lack of a global time coordinate should not allow to consider such a symmetry.

 

[kodama]

Which conclusion?

Gravity should be locally CPT invariant, globally the lack of a global time coordinate should not allow to consider such a symmetry.

this"Starting from the CPT invariance of physical laws, we transform matter into antimatter in the equations of both electrodynamics and gravitation. In the former case, the result is the well-known change of sign of the electric charge. In the latter, we find that the gravitational interaction between matter and antimatter is a mutual repulsion, i.e. antigravity appears as a prediction of general relativity when CPT is applied."

 

[mfb]

arXiv version

What he does looks odd. Anyway, the conclusion violates GR and it is in disagreement with experiments.

Also, what happens to black holes? They don't have a matter/antimatter difference, do they attract matter or antimatter? What happens to mesons, which are neither matter nor antimatter? What about electrons, are they matter or antimatter, and why?

 

[kodama]

arXiv version

What he does looks odd. Anyway, the conclusion violates GR and it is in disagreement with experiments.

Also, what happens to black holes? They don't have a matter/antimatter difference, do they attract matter or antimatter? What happens to mesons, which are neither matter nor antimatter? What about electrons, are they matter or antimatter, and why?

when you say violates experiments, are there experiments that prove antimatter falls down? and on observation that could explain is matter antimatter asymmetry and dark energy. if half the galaxies are antimatter and repel matter galaxies like milky way no need to baryogenesis

 

[mfb]

are there experiments that prove antimatter falls down?

Indirectly, as normal matter is 99% energy that does not fit clearly to "matter"/"antimatter" categories. See above.

Repulsive antimatter would still leave the question what separated antimatter and matter in the first place - the gravitational influence of individual particles is way too small.

 

[ohwilleke]

I would be very surprised if anti-matter and matter interacted differently via gravity. Among other things, this should have been discernible in the behavior of mesons and anti-neutrinos in Earth's gravitational field if it were true.

 

[kodama]

I would be very surprised if anti-matter and matter interacted differently via gravity. Among other things, this should have been discernible in the behavior of mesons and anti-neutrinos in Earth's gravitational field if it were true.

did u read the paper? anything wrong with his theory?

 

[ohwilleke]

Wikipedia has a nice review of the literature on the issue of whether anti-matter is identical to ordinary matter or repels ordinary matter with an equal an opposite force.

https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

In particular, it says this with regard to CPT:

The CPT theorem implies that the difference between the properties of a matter particle and those of its antimatter counterpart is completely described by C-inversion. Since this C-inversion doesn't affect gravitational mass, the CPT theorem predicts that the gravitational mass of antimatter is the same as that of ordinary matter.[11] A repulsive gravity is then excluded, since that would imply a difference in sign between the observable gravitational mass of matter and antimatter.

citing M.J.T.F. Cabbolet Elementary Process Theory: a formal axiomatic system with a potential application as a foundational framework for physics underlying gravitational repulsion of matter and antimatter, Annalen der Physik 522(10), 699-738 (2010).

 

[kodama]

Wikipedia has a nice review of the literature on the issue of whether anti-matter is identical to ordinary matter or repels ordinary matter with an equal an opposite force.

https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

In particular, it says this with regard to CPT:
citing M.J.T.F. Cabbolet Elementary Process Theory: a formal axiomatic system with a potential application as a foundational framework for physics underlying gravitational repulsion of matter and antimatter, Annalen der Physik 522(10), 699-738 (2010).

https://arxiv.org/pdf/1103.4937v1.pdf

in the paper V is arguing that GR extended with CPT, it is the PT in CPT, namely antimatter as time going backwards, is what causes it to be repulsive to ordinary matter. antimatter lives in a T inverted spacetime

in this new GR+CPT, gravitational charge does NOT equal mass but his new equation, where antimatter = -1, which is not negative mass but CPT where T is inverted for antimatter. pAGE5

 

[kodama]

Indirectly, as normal matter is 99% energy that does not fit clearly to "matter"/"antimatter" categories. See above.

Repulsive antimatter would still leave the question what separated antimatter and matter in the first place - the gravitational influence of individual particles is way too small.

i think the idea is not that an individual electron would repel an individual positron gravitationally moments after the big bang, but that among baryonic matter, half of all baryonic matter in the entire universe is matter which would repel the other half antimatter gravitationally, as it would be electrically neutral, after big bang. and half the galaxies are antimatter which repel galaxies made of matter, which would give effects similar to dark energy. no need for baryogenesis in the SM.

 

[kodama]

I would be very surprised if anti-matter and matter interacted differently via gravity. Among other things, this should have been discernible in the behavior of mesons and anti-neutrinos in Earth's gravitational field if it were true.

if neutrinos are majorana fermions they would be their own antiparticle.

 

[mfb]

i think the idea is not that an individual electron would repel an individual positron gravitationally moments after the big bang, but that among baryonic matter, half of all baryonic matter in the entire universe is matter which would repel the other half antimatter gravitationally, as it would be electrically neutral, after big bang. and half the galaxies are antimatter which repel galaxies made of matter, which would give effects similar to dark energy. no need for baryogenesis in the SM.

Those galaxies would not form in the first place. There is no mechanism that would separate matter and antimatter. The universe doesn't start with "here is matter, and antimatter is over there".

A questionable approach (see @ohwilleke), that does not agree with experiments at all (see 99% matter is not from quark masses) and has problems to explain the observed baryon asymmetry. Uh, well...

 

[kodama]

Those galaxies would not form in the first place. There is no mechanism that would separate matter and antimatter. The universe doesn't start with "here is matter, and antimatter is over there".

A questionable approach (see @ohwilleke), that does not agree with experiments at all (see 99% matter is not from quark masses) and has problems to explain the observed baryon asymmetry. Uh, well...

i don't necessarily have all the answers to your objections, but is the reasoning in that paper sound? does his conclusion follow from his premises?

obviously if experiments showed antiatoms fell up, then the binding energy in a proton made of anti-quarks does not alter the fact that anti-quarks create an inverted spacetime that is opposite in effect to quarks in a proton. and perhaps the big bang model can be modified to take into effect gravitational repulsive effects of antimatter should experiments show that is the case.

there are several research groups i.e Alpha

http://newscenter.lbl.gov/2013/04/30/antimatter-up-down/

Does Antimatter Fall Up or Down?
The atoms that make up ordinary matter fall down, so do antimatter atoms fall up? Do they experience gravity the same way as ordinary atoms, or is there such a thing as antigravity?

These questions have long intrigued physicists, says Joel Fajans of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), because “in the unlikely event that antimatter falls upwards, we’d have to fundamentally revise our view of physics and rethink how the universe works.”

So far, all the evidence that gravity is the same for matter and antimatter is indirect, so Fajans and his colleague Jonathan Wurtele, both staff scientists with Berkeley Lab’s Accelerator and Fusion Research Division and professors of physics at the University of California at Berkeley – as well as leading members of CERN’s international ALPHA experiment – decided to use their ongoing antihydrogen research to tackle the question directly. If gravity’s interaction with anti-atoms is unexpectedly strong, they realized, the anomaly would be noticeable in ALPHA’s existing data on 434 anti-atoms.

The first results, which measured the ratio of antihydrogen’s unknown gravitational mass to its known inertial mass, did not settle the matter. Far from it. If an antihydrogen atom falls downward, its gravitational mass is no more than 110 times greater than its inertial mass. If it falls upward, its gravitational mass is at most 65 times greater.

What the results do show is that measuring antimatter gravity is possible, using an experimental method that points toward much greater precision in future. They describe their technique in the April 30, 2013 edition of Nature Communications.

How to measure a falling anti-atom

ALPHA creates antihydrogen atoms by uniting single antiprotons with single positrons (antielectrons), holding them in a strong magnetic trap. When the magnets are turned off, the anti-atoms soon touch the ordinary matter of the trap’s walls and annihilate in flashes of energy, pinpointing when and where they hit. In principle, if the experimenters knew an anti-atom’s precise location and velocity when the trap is turned off, all they’d have to do is measure how long it takes to fall to the wall.

ALPHA’s magnetic fields don’t turn off instantly, however; almost 30-thousandths of a second pass before the fields decay to near zero. Meanwhile flashes occur all over the trap walls at times and places that depend on the anti-atoms’ detailed but unknown initial locations, velocities, and energies.
Wurtele says, “Late-escaping particles have very low energy, so gravity’s influence is more apparent on them. But there were very few late escaping anti-atoms; only 23 of the 434 escaped after the field had been turned off for 20-thousandths of a second.”

 

[ohwilleke]

https://arxiv.org/pdf/1103.4937v1.pdf

in the paper V is arguing that GR extended with CPT, it is the PT in CPT, namely antimatter as time going backwards, is what causes it to be repulsive to ordinary matter. antimatter lives in a T inverted spacetime

in this new GR+CPT, gravitational charge does NOT equal mass but his new equation, where antimatter = -1, which is not negative mass but CPT where T is inverted for antimatter. pAGE5

After reading the paper, I don't think that the reasoning is sound. If you reverse PT, then you are getting the properties of anti-matter from the perspective of anti-matter moving backward in time. Gravity has mutual attraction when bodies are moving forward in time. If you "rewind the videotape" to demonstrate its behavior for particles viewed as moving backward in time, then, yes, it is mutually repulsive. But, this feature is true of both matter and antimatter viewed as moving backward in time. So, the reasoning is unsound.

 

[kodama]

After reading the paper, I don't think that the reasoning is sound. If you reverse PT, then you are getting the properties of anti-matter from the perspective of anti-matter moving backward in time. Gravity has mutual attraction when bodies are moving forward in time. If you "rewind the videotape" to demonstrate its behavior for particles viewed as moving backward in time, then, yes, it is mutually repulsive. But, this feature is true of both matter and antimatter viewed as moving backward in time. So, the reasoning is unsound.

antimatter is equivalent to matter going back in time, not antimatter going back in time.

 

[ohwilleke]

But viewed that way you have to think of antimatter from a backward looking perspective. The antimatter is moving backward and from that perspective is mutually repulsive. The matter is moving forward and from that perspective is mutually attractive. There is no contradiction. If one treats all particles as moving forward in time, which is how we observe them, then gravity is attractive.

 

[kodama]

But viewed that way you have to think of antimatter from a backward looking perspective. The antimatter is moving backward and from that perspective is mutually repulsive. The matter is moving forward and from that perspective is mutually attractive. There is no contradiction. If one treats all particles as moving forward in time, which is how we observe them, then gravity is attractive.

ultimately experiments on anti-hydrogens are in the works, ie ALPHA.
physicists who work on ALPHA do consider the real possibility anti-hydrogen will fall up, and have described how they plan to produce, trap, slow down and then study anti-hydrogen effects.

suppose anti-hydrogens fall up at -G, and this is confirmed under review and by other experiments.

How would you modify GR to explain anti-matter falling up?

 

[ohwilleke]

Certainly, there is no harm in doing experiments like ALPHA. Far better to rely on experience than reason. You could add a Dirac delta function to the stress-energy tensor to code matter v. antimatter, I suppose, although I am sure that there are at least half a dozen ways to accomplish it, only some of which would be mathematically consistent. You could also probably change the sign the mass in anti-matter to a negative, but that would screw up the equivalence principle unless it was restated in terms of mass squared rather than mass.

You'd have other problems too, however. For example, if anti-matter were repulsive, then any heavy particle decays generating matter-antimatter pairs would spew the antimatter out of the black hole leading to more loss of mass than would be predicted by Hawking radiation that was exclusively antimatter, which there is no good reason to think is actually happening. Something similar would happen when matter-antimatter pairs are created in nuclear reactions in stars, so we'd expect stars to spew a constant mist of antimatter as its nuclear reactions progressed, which again, is not observed.

 

[mfb]

physicists who work on ALPHA do consider the real possibility anti-hydrogen will fall up, and have described how they plan to produce, trap, slow down and then study anti-hydrogen effects.

Of course they do, that is the whole point of the experiment: rule out any remaining doubts that antimatter falls down.

How would you modify GR to explain anti-matter falling up?

You cannot. The equivalence principle is fundamental to GR. Violate that and you need a completely new theory.

 

[kodama]

Of course they do, that is the whole point of the experiment: rule out any remaining doubts that antimatter falls down.You cannot. The equivalence principle is fundamental to GR. Violate that and you need a completely new theory.

well this paper

CPT symmetry and antimatter gravity in general relativity
M. Villata

Published 28 March 2011 • Europhysics Letters Association
EPL (Europhysics Letters), Volume 94, Number 2
Abstract
The gravitational behavior of antimatter is still unknown.

claims that GR needs only a small well-motivated change, but yes it would violate the EP but still GR +CPT

 

[mfb]

Villata seems to be quite alone with that claim.

Comment to a paper [arXiv:1103.4937] of M. Villata on antigravity

In a recent paper of M. Villata [arXiv:1103.4937], it is claimed that "antigravity appears as a prediction of general relativity when CPT is applied." However, the present paper argues that Villata puts the cart before the horse qua methodology, and that the resulting theory cannot be reconciled with the ontological presuppositions of general relativity. The conclusion is that Villata's suggestion for the physics that might underlie a gravitational repulsion of matter and antimatter is not acceptable in its current state of development.

Other citations:

7 times: Dragan Slavkov Hajdukovic. And guess what, Villata also cites Hajdukovic three times.
2 times Villata - selfcitations
Jaume Giné - Towards a quantum universe, in "General Physics", which is mainly a place for crackpot papers
Martin Tajmar - that guy who claims to have a "Process for the generation of a gravitational field and a gravitational field generator"
Michael Dopita - summarizing several publications in the journal
4 experimental papers - with long lists of papers that discuss any differences from the expected behavior, Villata is one of them

Summary: Apart from Hajdukovic, no one really takes that paper seriously.

 

[kodama]

Villata seems to be quite alone with that claim.

Comment to a paper [arXiv:1103.4937] of M. Villata on antigravityOther citations:

7 times: Dragan Slavkov Hajdukovic. And guess what, Villata also cites Hajdukovic three times.
2 times Villata - selfcitations
Jaume Giné - Towards a quantum universe, in "General Physics", which is mainly a place for crackpot papers
Martin Tajmar - that guy who claims to have a "Process for the generation of a gravitational field and a gravitational field generator"
Michael Dopita - summarizing several publications in the journal
4 experimental papers - with long lists of papers that discuss any differences from the expected behavior, Villata is one of them

Summary: Apart from Hajdukovic, no one really takes that paper seriously.

true as of right now. but in the event that the ALPHA experiment at Berkley shows antiatoms falling up, I'm sure that paper would get more citations, maybe even win the author a nobel prize. if antihydrogen falls down then that paper would be lost in obscurity.

there are more than 500+ papers on the diphoton excess 750 gev, with early papers getting scores and scores of citations on this from later papers. the rumor from LHC is that this excess is a statistical fluke. so experimental results go a long way to determine a paper's citation.
500+ papers with early papers on 750 diphoton bump getting scores of citations, all for a fluke.

 

[mfb]

but in the event that the ALPHA experiment at Berkley shows antiatoms falling up, I'm sure that paper would get more citations

Yes

maybe even win the author a nobel prize

No. There are other ideas how antimatter could fall upwards - ideas that are worked out much better than Kodama's paper.

if antihydrogen falls down then that paper would be lost in obscurity.

It is lost in obscurity already.

the rumor from LHC is that this excess is a statistical fluke

Don't trust rumors.

500+ papers with early papers on 750 diphoton bump getting scores of citations, all for a fluke.

All for possible models of new physics, and all 500 are not in disagreement with observations, unlike Kodama's paper.

 

[kodama]

YesNo. There are other ideas how antimatter could fall upwards - ideas that are worked out much better than Kodama's paper.It is lost in obscurity already.
Don't trust rumors.All for possible models of new physics, and all 500 are not in disagreement with observations, unlike Kodama's paper.

i was alluding to this by Jester. we'll know by Friday with an official announcement from CERN.http://resonaances.blogspot.com/Friday, 29 July 2016
After the hangover

The loss of the 750 GeV diphoton resonance is a big blow to the particle physics community. We are currently going through the 5 stages of grief, everyone at their own pace, as can be seen e.g. in this comments section. Nevertheless, it may already be a good moment to revisit the story one last time, so as to understand what went wrong.

In the recent years, physics beyond the Standard Model has seen 2 other flops of comparable impact: the faster-than-light neutrinos in OPERA, and the CMB tensor fluctuations in BICEP. Much as the diphoton signal, both of the above triggered a binge of theoretical explanations, followed by a massive hangover. There was one big difference, however: the OPERA and BICEP signals were due to embarrassing errors on the experiments' side. This doesn't seem to be the case for the diphoton bump at the LHC. Some may wonder whether the Standard Model background may have been slightly underestimated, or whether one experiment may have been biased by the result of the other... But, most likely, the 750 GeV bump was just due to a random fluctuation of the background at this particular energy. Regrettably, the resulting mess cannot be blamed on experimentalists, who were in fact downplaying the anomaly in their official communications. This time it's the theorists who have some explaining to do.

Why did theorists write 500 papers about a statistical fluctuation? One reason is that it didn't look like one at first sight. Back in December 2015, the local significance of the diphoton bump in ATLAS run-2 data was 3.9 sigma, which means the probability of such a fluctuation was 1 in 10000. Combining available run-1 and run-2 diphoton data in ATLAS and CMS, the local significance was increased to 4.4 sigma. All in all, it was a very unusual excess, a 1-in-100000 occurrence! Of course, this number should be interpreted with care. The point is that the LHC experiments perform gazillion different measurements, thus they are bound to observe seemingly unlikely outcomes in a small fraction of them. This can be partly taken into account by calculating the global significance, which is the probability of finding a background fluctuation of the observed size anywhere in the diphoton spectrum. The global significance of the 750 GeV bump quoted by ATLAS was only about two sigma, the fact strongly emphasized by the collaboration. However, that number can be misleading too. One problem with the global significance is that, unlike for the local one, it cannot be easily combined in the presence of separate measurements of the same observable. For the diphoton final state we have ATLAS and CMS measurements in run-1 and run-2, thus 4 independent datasets, and their robust concordance was crucial in creating the excitement. Note also that what is really relevant here is the probability of a fluctuation of a given size in any of the LHC measurement, and that is not captured by the global significance. For these reasons, I find it more transparent work with the local significance, remembering that it should not be interpreted as the probability that the Standard Model is incorrect. By these standards, a 4.4 sigma fluctuation in a combined ATLAS and CMS dataset is still a very significant effect which deserves a special attention. What we learned the hard way is that such large fluctuations do happen at the LHC... This lesson will certainly be taken into account next time we encounter a significant anomaly.

 

[kodama]

Certainly, there is no harm in doing experiments like ALPHA. Far better to rely on experience than reason. You could add a Dirac delta function to the stress-energy tensor to code matter v. antimatter, I suppose, although I am sure that there are at least half a dozen ways to accomplish it, only some of which would be mathematically consistent. You could also probably change the sign the mass in anti-matter to a negative, but that would screw up the equivalence principle unless it was restated in terms of mass squared rather than mass.

You'd have other problems too, however. For example, if anti-matter were repulsive, then any heavy particle decays generating matter-antimatter pairs would spew the antimatter out of the black hole leading to more loss of mass than would be predicted by Hawking radiation that was exclusively antimatter, which there is no good reason to think is actually happening. Something similar would happen when matter-antimatter pairs are created in nuclear reactions in stars, so we'd expect stars to spew a constant mist of antimatter as its nuclear reactions progressed, which again, is not observed.

something like this may have happened in a modified new big bang theory. in this newer theory to take account of ALPHA, matter and antimatter were created equally. no need for baryogenesis. the first moments after big bang gravitational repulsion between the two is what separated them, not baryogenesis followed by inflation.

 

[haushofer]

Wikipedia has a nice review of the literature on the issue of whether anti-matter is identical to ordinary matter or repels ordinary matter with an equal an opposite force.

https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

In particular, it says this with regard to CPT:
citing M.J.T.F. Cabbolet Elementary Process Theory: a formal axiomatic system with a potential application as a foundational framework for physics underlying gravitational repulsion of matter and antimatter, Annalen der Physik 522(10), 699-738 (2010).

Cabbolet his PhD-defence was actually blocked by 't Hooft; he then had to go to another faculty, I believe in Belgium, to get his degree. I once tried to read his PhD-thesis, but I couldn't make much of it. Not sure what that means :P

 

[rootone]

I would not be surprised if turns out that the missing antimatter somehow explains dark matter.