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> > PS- hate the article title, pure vague clickbait

> I agree. From the article:

> > Yet physicists have found nothing amiss, no conclusive sign that antimatter particles — which are just the oppositely charged twins of familiar particles — obey different rules.

> So no surprises. Also, the "near absolute zero" is true, but it's just to make the experiment easier, it's not important from the theoretical point of view. Anyway, it's an interesting experiment in spite of the press article title.

I'm sorry but did you actually read the article? The first quote is from the very first paragraph talking about physicists in general. And the cooling to near absolute zero was not "just to make the experiment easier." And it definitely is important.

The surprise, in case you haven't read the article, is that one expects spectral lines of atoms in an ultra dense fluid (i.e. supercooled helium) to be smudged due to the interactions with surrounding atoms. But, when performing laser spectroscopy on hybrid atoms (regular nucleus but with antiprotons taking the place of electrons) the spectral lines narrowed instead of widened. See, for example, this paragraph:

> Where the spectral lines of most atoms would have gone completely haywire in the increasingly dense fluid, widening perhaps a million times, the Frankenstein atoms did the opposite. As the researchers lowered the helium bath to icier temperatures, the spectral smudge narrowed. And below about 2.2 kelvins, where helium becomes a frictionless “superfluid,” they saw a line nearly as sharp as the tightest they had seen in helium gas. Despite presumably taking a battering from the dense surroundings, the hybrid matter-antimatter atoms were acting in improbable unison.

This was a big surprise. That's why the next two lines are:

> Unsure what to make of the experiment, Sótér and Hori sat on the result while they mulled over what could have gone wrong.

> “We continued to argue for many years,” Hori said. “It was not so easy for me to understand why this was the case.”

So, no, the article title is not clickbait and, yes, this is "important from the theoretical point of view".

<handwaving>The sharper espectral lines doesn't look too surprising, because in the superfluid liquid the Helium atoms "want" to be in the state creates the Bose condensate, so they don't "want" to colide too much with the disolved impurities. So the impurities are not disturbed too much and you get a nice spectrum.</handwaving>

You may not like my handwavig, and in that case I agree that my handwaving is not a proof. Perhaps this has more info: https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensa...

Anyway, other teams already used superfluid helium to make spectroscopy of molecules (without antimater). The second result in my Google search is https://www.tandfonline.com/doi/full/10.1080/23746149.2018.1...

> For more than two decades, encapsulation in superfluid helium nanodroplets has served as a reliable technique for probing the structure and dynamics of molecules and clusters at a low temperature of ≈0.37 K. Due to weak interactions between molecules and the host liquid helium, good spectral resolution can usually be achieved, making helium droplets an ideal matrix for spectroscopy in a wide spectral range from infrared to ultraviolet.

Is this some kind of superfluidy Mossbauer-like bulk effect?

Side question. I understand the positive and negative charges, but when we say "+1" or "-1" what are the units? I never understood that part. an electron is -1 and a proton is +1, but what makes them equal? Why / how do all these things of varying sizes and properties have the same magnitude for charges?

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

And, more specifically:

https://en.wikipedia.org/wiki/Elementary_charge#Charges_less...

Basically, quarks seem to have charges that are 1/3 e. However, they can only be stable in groups of three, and those groups must have an integer value. So the only possibilities are -1, 0, and 1.

As to why the above is true, it just seems to be a rule. We don't have any good reasoning for why that rule exists.

mesons are composed of two quarks and can have neutral or non-neutral charge. baryons are composed of three quarks and can have neutral or non-neutral charge. both mesons and baryons are classified as hadrons

charge, baryon number, isospin and strangeness are all related by the Gell-Mann-Nishijima formula[1].

the overarching principle underlying this is that in quantum chromodynamics, the theory of the strong interaction, quarks are representations of an underlying SU(3) gauge group containing color charge (a quantum number) and electric charge quantized as -1/3e and +2/3e. QCD is a gauge theory (like all other theories of nature) and the gauge boson, the gluon, also pops out of demanding the theory be invariant under local SU(3) gauge transformations.

that said, no one has any clue why all of our physical theories are gauge theories :-)

https://en.wikipedia.org/wiki/Gell-Mann%E2%80%93Nishijima_fo...

very interesting! I am rather unfamiliar with quantum chromodynamics but I am going to enjoy the gauge theory rabbit hole

Would a theory of the history of the universe be a non-gauge theory since there was fast initial inflation, a relative slowdown, and now accelerating expansion again? Nothing seems conserved here. It seems symmetries were broken as the forces split apart, anti-particles were annihilated, etc

I am now visualizing this as a series of assert() statements that abort particle action when a constraint is not met.

I would expect the conservation rules to be statically encoded in the type system.

It should be statically typechecked of course, but especially in the quantum physics code we couldn't encode all the invariants correctly and runtime exceptions can still occur in rare occasions. A fix has been proposed and will hopefully be merged in time for the next universe release window.