CPT symmetry and antimatter gravity in general relativity

[ohwilleke]

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

In a not entirely unrelated point, one of the most important pieces of big picture information that is missing in our understanding of the cosmology of the universe is the ratio of neutrinos to antineutrinos in the universe. We have quite decent estimates of the total number of quarks, anti-quarks, charged leptons and charged anti-leptons in the universe, and we have quite decent estimates of the total number of neutrinos in the universe. But, we don't have any decent estimates of the ratio of neutrinos to antineutrinos in the universe.

This is a problem because in the Standard Model baryon number (which can be determined from the number of quarks and antiquarks) is conserved and we can calculated B, and lepton number (which can be determined from the number of charged leptons, charged anti-leptons, neutrinos and antineutrinos) is also separately conserved (with one hypothetical Standard Model interaction that only occurs at very high energies and has never been observed preserving only B-L but neither independently). We also know the total estimated mass of dark matter and hence can calculate the number of dark matter particles for any given dark matter mass, but we don't know if dark matter has baryon number, lepton number or something else.

But, even if dark matter has lepton number, the number of neutrinos and antineutrinos so greatly outnumber the combined number of quarks, anti-quarks, charged leptons, charged anti-leptons, and dark matter particles (with any sensible estimate for dark matter mass) that absolute value of L and B-L and B+L for the universe is completely dominated by the ratio of neutrinos to antineutrinos in the universe. So, we're missing a pretty key data point to understanding the overall matter-antimatter balance of the universe. (And, of course, it only gets more complicated if neutrinos are Majorana particles.)

 

[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.

the 750 diphoton has gone away with more data. the Alpha experiment hasn't been done yet, not sure when it will be.

 

[ohwilleke]

There is now strong experimental evidence that antimatter behaves gravitationally the same way that matter does.

http://arxiv.org/abs/1508.04377 (the preprint attached was accepted for publication in its most recent version after peer review).

 

[mfb]

I don't understand where they get the $\gamma^2$ from in equation 5 or how they get equation 6.

The gravitational potential difference is ~10 MJ/kg, or 50 µeV/electron. Why would such a tiny difference lead to O(10^-4) differences in synchrotron radiation?

I like this paper (PDF) they cite which discusses the potential influence of the gravitational potential on kaon mixing. This mixing is very sensitive to mass differences, there I understand the method.

 

[ohwilleke]

I like the kaon paper as well.