Interesting background read: https://en.m.wikipedia.org/wiki/Hypernucleus
Well, I suppose, radioactive decay is of negative use in chemistry and engineering.
Also, heavy water is typically slightly radioactive due to it usually containing tritiated water (T2O), though regular water can also contain that.
Apparently, swapping 20% of your cells' water with heavy water is survivable, but if you try this, don't blame me if you go sterile (cell mitosis will likely be affected).
Exploring the Universe’s Origins: The Big Bang should have created equal amounts of matter and antimatter, yet our universe is predominantly matter. Studying antimatter helps scientists investigate this imbalance, shedding light on the fundamental laws of physics.
Medical Applications: Antimatter plays a role in medical imaging techniques like Positron Emission Tomography (PET) scans, which are used to detect conditions such as cancer.
Additionally, statistically speaking, such a degree of order is highly unlikely since it would have much lower entropy compared to an homogeneous mix.
It is much more likely that there is some unknown physical process that broke the symmetry between matter and anti-matter and so our universe is matter rich and anti-matter poor.
Like maybe the matter went this way, and the antimatter went that way in spacetime? Or maybe all the antimatter went before the Big Bang and the matter went after?
I mean that’s wild but it would fix the symmetry problem!
Which ML technique are they using? Could it be XGBoost, because I heard CERN is using it?
https://arxiv.org/abs/2410.17769
And in fact, they used XGBoost.
PS: By exotic here it I use the term as used by particle physicists which just mean not your ordinary stuff discussed in the "popular" working groups. Not the linguistic meaning of the word exotic.
"unusual and exciting because of coming (or seeming to come) from far away, especially a tropical country"
That doesn't seem too far from the use of it in physics. The "tropical country" part is clearly optional but could be replaced by "especially a special group of scientists".
Someone can correct me if I'm wrong, but the significance of this is mostly just further confirmation of the predictions of the standard model. The standard model says such particles should exist and now that we've created them, we've confirmed that they do indeed exist.
I don't think there's much practical application beyond further refinement of theoretical physics and ruling out other candidate theories.
The vast majority of applications, if any, will be extremely niche sensing applications. They are useful to further probe the edges of our knowledge of physics and look at the corner cases where our models give confused shrugs and odd answers.
It's not going to power a warp drive.
> Hypernuclei are exotic nuclei formed by a mix of protons, neutrons and hyperons, the latter being unstable particles containing one or more quarks of the strange type.Oh god I just noticed it's from 16 years ago... I'm getting old
Does this prove that antimatter is necessary for theories of gravity to concur with other observations?
Do the observed properties of antimatter particles correspond with antimatter as the or a necessary nonuniform correction factor to theories of gravity?
If you want some antimmater, you can go to your nearby physics suply store and buy some radioactive material that produce positrons. It's quite easy. (Radioactive material may be dangerous. Don't fool with that!) If you want antiprotons or antihydrogen, you need a huge particle acelerator. They make plenty of antiprotons in the CERN, to make colisions. They are very difficult to store, so they survive a very short time on Earth.
Dark matter is very different. We have some experimental resuls that don't match the current physics theories. The current best guess is that there is some matter that we can't see for some reason. Nobody is sure what it is. Perhaps it's made of very dark big objects or perhaps it's made of tiny particles that don't interact with light. (I'm not sure the current favorite version in the area.) Anyway, some people don't like "dark matter" and prefer to change the theories, but the proposed new theories also don't match the experimental results.
If this theory were true, tiny nuggets of this antimatter would be passing through the solar system all the time. Perhaps a future society could detect them and somehow trap some for use as an energy source.
https://indico.fnal.gov/event/6199/contributions/94686/attac...
(that was 2013; perhaps observations since have made it less likely)
2021 paper: https://arxiv.org/abs/2105.08719
2020 paper: https://www.researchgate.net/publication/342573954_Antimatte... ("a large region of the parameter space remains unconstrained, most notably for nuclear-dense objects.")
My pet conjecture (it's not detailed enough to be a hypothesis) is that this is related to the baryon asymmetry problem.
The antimatter symmetry problem is more than just baryons, despite the name, as we also have more electrons than positrons, not just more protons/neutrons than anti-protons/anti-neutrons.
There's a few possibilities:
1) the initial value just wasn't zero (an idea I heard from Sabine Hossenfelder)
2) the baryon number is violated in a process that requires conservation of charge
This would suggest antiprotons or antineutrons do something which involves the positron at the same time, so perhaps the anti-neutron is weirdly stable or something — neutron decay is a weak force process, and that can slightly violate the charge conjugation parity symmetry, so this isn't a completely arbitrary conjecture.
If we've got lots of (for example) surprise-stable anti-neutrons all over the place… it's probably not a perfect solution to the missing mass, but it's the right kind of magnitude to be something interesting to look at more closely.
3) the baryon number (proton/neutron/etc.) and/or lepton number (electron/positron/muon/etc.) is violated in a process that does not require conservation of charge.
If you have some combination of processes which don't each conserve charge, you're likely to get some net charge to the universe (unless the antiproton process just happens to occur at the same rate as the positron process); in quantum mechanics I understand such a thing is genuinely meaningless, while in GR this would contribute to the stress energy tensor in a way that looks kinda like dark energy.
But like I said, conjecture. I'm not skilled enough to turn this into a measurable hypothesis.
Virtual particles: https://en.wikipedia.org/wiki/Virtual_particle :
> As a consequence of quantum mechanical uncertainty, any object or process that exists for a limited time or in a limited volume cannot have a precisely defined energy or momentum. For this reason, virtual particles – which exist only temporarily as they are exchanged between ordinary particles – do not typically obey the mass-shell relation; the longer a virtual particle exists, the more the energy and momentum approach the mass-shell relation.
Unfortunately the maths of QM doesn't play nice with the maths of GR, which is also why zero-point effects are either renormalised to exactly zero or otherwise predict an effect 10^122 times larger than observed.
Anyway, I think there is still a chance that dark matter is antineutrinos. I'm not sure if it has been ruled out.
Or buy some bananas. You'll get a positron every once in a while from the occasional Potassium-40 decay.
A few sources like https://alpha.web.cern.ch/science/positron-source and https://ifj.edu.pl/private/jdryzek/page_r12.html recomend sodium 22.
It seems a bit more complicated than that, mostly because the vulgarization often available too is quite bad to explain the issue.
My understanding:
- Our current theories fail to predict/match an array of observations, as if more matter than what we can detect exist. Some scientists called that the "dark matter problem", that's what most physicists working on the subject refer to when they talk about "dark matter".
- Every theory you talked about: dark matter big objects, dark matter particles AND the "change the theories" (i guess you talk about the Modified Newtonian dynamics, where you alter Newton's second law at low speed to match some observations) are dark matter theories: theories that tries to explain why the universe act as it is, not matching our current theories, either by adding new things, or by modifying our discovered laws to match our observations. Each of those theories have multiple branch investigated.
- the "dark matter particle theory" is sometime vulgarized as "dark matter" on podcasts or in books/articles. This is because more scientists work on particle physics than on gravity or astrophysics (my country present like 3 astrophysics thesis each year, and dozens of particle physics thesis). I think this caused a huge misunderstanding.
- Some people with a common understanding (like mine, i meant non-physicists, it's absolutely not derogatory) like MOND because philosophically it is quite nice, and also tend to draw in people with minority/anti-etablishment habitus[0] (cf: most physicists working on those subjects are particle physicists). I'm not saying this theory is worse than the others at all, i'm just saying that the kind of layperson drawn to it can be _really_ sure they're right and profess their beliefs everywhere, and sometime claim that "MOND isn't dark matter", when they really confuse dark matter as a problem to be solved with "dark matter particle theory". Misunderstanding happen to everyone btw, it's really not a big issue.
In case you did not talk about MOND but about theories that claim that the issue are with our tools to observe at a distance, some theories include that to explain some of the inconsistencies, never all of them, and those theories seems to really be a minority atm, so hopefull it wasn't about that.
[0] Also, those habitus seems to draw in grifters who know they can make quick bucks by selling books/conferences if they look convincing enough, which is why MOND has a weird reputation now, but absolutely serious physicists and mathematicians work on the subject very, very seriously.
MOND is a non-relativistic theory. It's not even able to explain the orbit of mercury, gravitational lensing or black holes.
It's the equivalent of hot gluing jet engines to a roman quadriga, it won't fly.
Well obviously, it's literally in the name.
A relativistic version of the theory is: https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93...
There are more elegant ways of doing it (ex: TeVeS), but before looking at the best way to reconcile general relativity and MOND, something we know is possible, it is important to make sure that MOND works at the scales it is supposed to work with. Currently, it doesn't, but dark matter doesn't either. More research is needed, as they say.
Personally, I don't think MOND will be the solution. But I don't think it's going to be dark matter either.
1. We don't have a a way to unify relativity and quantum mechanics yet 2. Dark matter and MOND effects show up at extremely low accelerations.
I have a hunch it's going to need a theory of quantum gravity to properly solve this.
A century ago, quantum mechanics was initially formalized to explain the uktraviolet catastrophe of blackbody emissions.
The difference between the classical emissions curve and the quantum based emissions curbe is very similar to the correction factor applied by MOND. I don't think that's a coincidence.
To me they are as right as people working on lambdaCDM or dark fluid, as long as none of those theory is able to predict anything.
And some MOND derivatives are interesting, TeVeS is mathematically nice. I'm pretty sure most people working on those do it for the math more than to be correct tbh, but people way more competent than me work on this subject and I would not dare claim knowing they're wrong or lying.
The idea of dark matter is that the problem is caused by matter we can't see. We assume the standard equations and from the rotation of the galaxies we have some missing mass. But we have a few equations, like gravitational lens, where we also can meassure missing mass and we can compare the results of the different methods. There are a few examples in https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics#Ou...
MOND is an alternative solution to the same problem.
I expect that most people working in dark matter are astronomers an cosmologist. I don't expect many particle phycicist realy care about dark matter. I've seen a lot of claim of particle phycicist that their new pet theory may be the dark matter, but it's mostly overhype to try to get more grant money.
And dark matter is an area of research and experiment in particle physics (at least it was 10 years ago)
Antimatter definitely exists, it is detectable, and used; e.g, PET scans use positrons (anti-electrons), and there have been experiments (only in animal models last I knew) with anti-proton radiotherapy for cancers.
This is the first evidence of a particular configuration of antimatter, not the first evidence of antimatter.
I had confused Antimatter in particle theory (where there is no gravity) and Dark matter, which has no explanation in particle theory and maybe probably shouldn't be necessary for a unified model that describes n-body gravity at astrophysical and particle scales.
From https://news.ycombinator.com/item?id=42369294#42371561 :
> One theory of dark matter is that it's strange quark antimatter.
It seems I had my Antimatter confused with mah Dark matter.
Antimatter: https://en.wikipedia.org/wiki/Antimatter
Dark matter: https://en.wikipedia.org/wiki/Dark_matter
Antimass:
I and the Internet have never heard of antimass.
Negative mass: https://en.wikipedia.org/wiki/Negative_mass
Dark energy: https://en.wikipedia.org/wiki/Dark_energy
Dark fluid: https://en.wikipedia.org/wiki/Dark_fluid :
> Dark fluid goes beyond dark matter and dark energy in that it predicts a continuous range of attractive and repulsive qualities under various matter density cases. Indeed, special cases of various other gravitational theories are reproduced by dark fluid, e.g. inflation, quintessence, k-essence, f(R), Generalized Einstein-Aether f(K), MOND, TeVeS, BSTV, etc. Dark fluid theory also suggests new models, such as a certain f(K+R) model that suggests interesting corrections to MOND that depend on redshift and density
FWIU this Superfluid Quantum Gravity rejects dark matter and/or negative mass in favor of supervaucuous supervacuum, but I don't think it attempts to predict other phases and interactions like Dark fluid theory?
From "Show HN: Physically accurate black hole simulation using your iPhone camera" https://news.ycombinator.com/item?id=42191692 :
> Ctrl-F Fedi , Bernoulli, Gross-Pitaevskii:
>> "Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/
There's a newer paper on it.
Alternatives to general relativity > Testing of alternatives to general relativity: https://en.wikipedia.org/wiki/Alternatives_to_general_relati...
The new Sagittarius* black hole image with phase might help with discarding models unsupported by evidence. Are those knots or braids or fields around a vortical superfluidic attractor system? There doesn't at all appear to be a hard boundary Schwarzschild radius.
But that's about not dark matter not antimatter.
https://timeline.web.cern.ch/carl-anderson-discovers-positro...
And then there’s the exotic theory that at the big bang, regular matter went one direction in time and antimatter the opposite direction.
I wondered the same thing, but it doesn't work out. Rolling enough dice to get enough of the antimatter far enough away — by a combination of Heisenberg for most of it and local annihilation of what was left — is just too unlikely, given what we see. Boltzmann-brain levels of unlikely.
A universe that did that would have too much energy (from the mutual annihilation) once the orders and orders of magnitude of "extra" matter/antimatter interacted to make that likely/possible.
Wouldn't we also see clouds of antimatter just hanging around? What proportion of matter has ever interacted with anything else? My guess is "low".
The problem is there is no known reason for universe to exist. As such it could have been created in any configuration possible - including one where we observe matter, but antimatter is beyond event horizon.
For curiosity's sake: Wouldn't something like quantum mechanics defy that argument?
The TL;DR is that you can't actually get information out of a measurement of entangled quantum states placed at locations A and B without also transmitting classical information between A and B.
But good question!
[1] https://en.wikipedia.org/wiki/Quantum_teleportation
[2] https://www.forbes.com/sites/startswithabang/2020/01/02/no-w...