[Jarek Duda (OP)]

Nucleons being built of 3 quarks is a seen as a common knowledge.
So what happens with quarks when multiple nucleons bind into a nucleus?

This seems kind of a basic question, also about charge distribution in nuclei, but it is really tough to find any reliable materials about it - any thoughts?

Some more detailed questions:
- To model e.g. dueteron + neutron/proton scatterings, there are fitted ~40 parameters nucleon-focused models which require 3-body forces ( https://en.wikipedia.org/wiki/Three-body_force ), neglecting quarks - would we still need 3-body forces if including quarks into considerations?
- We know deuteron has large quadrupole moment ( https://en.wikipedia.org/wiki/Deuterium#Magnetic_and_electric_multipoles ), what naively requires multiple charges - why quarks are not considered here?
- Or: what is charge distribution of neutron ("built of 3 quarks")? I have seen some papers claiming positive charge and negative shell, e.g. http://www.actaphys.uj.edu.pl/fulltext?series=Reg&vol=30&page=119

[yor_on]

How come you always ask those difficult questions Jarek :)

Quarks have fractional values, and then you have the first link you used in where they define it as being in a 'stable superposition', this three body system. " The fundamental strong interaction does exhibit such behaviour, the most important example being the stability experimentally observed for the helium-3 isotope, which can be described as a 3-body quantum cluster entity of two protons and one neutron [PNP] in stable superposition "

All of that seem to point to new physics for me.
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"  These particles obey the Pauli exclusion principle. Fermions include all quarks and leptons, as well as all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions differ from bosons, which obey Bose–Einstein statistics. "

So while the protons and neutron are superimposed the quarks should still follow the Pauli exclusion principle? As well as it becomes a stable  'three body system' ??

[Jarek Duda (OP)]

Why should I ask simple questions?
While "everybody knows proton and neutron are made of quarks", trying to ask nearly any question about the details ... there is usually just silence.

Starting with neutron - quarks mean some charge distribution, what exactly?
If searching literature, there are some papers (e.g. http://www.actaphys.uj.edu.pl/fulltext?series=Reg&vol=30&page=119 ) claiming positive core and negative shell:


Is it true?
What happens with quarks when binding into deuteron? We know it has large quadrupole moment ...
Three-body systems like for d-n scattering require three-body interactions in currently used models ... maybe it is an artifact of neglecting quarks?

I got to these questions from considering soliton particle models, which suggests that baryon requires some charge (e.g. +2/3) - what gives nice intuitions e.g. why neutron is heavier than proton (because this charge needs to compensated to 0 what costs energy), or deuteron binding (shift of part of charge from proton to neutron, leading to observed quadrupole).

[yor_on]

Have to admit that I got curios to how they defined negative shell and positive charge, but it's behind a pay wall unfortunately.

 'Inside the neutron'   by Jo van den Brand and Peter de Witt Huberts
https://iopscience.iop.org/article/10.1088/2058-7058/9/2/27/pdf

As for the rest maybe Kryptid, Collin, BC or Evan has some ideas.
(I really miss JP when questions like this comes up:).

[yor_on]

Heh, that link you gave was awfully mathematical, wasn't it :)

But is it this you're thinking of? " A topological soliton, also called a topological defect, is any solution of a set of partial differential equations that is stable against decay to the "trivial solution". Soliton stability is due to topological constraints, rather than integrability of the field equations. The constraints arise almost always because the differential equations must obey a set of boundary conditions, and the boundary has a nontrivial homotopy group, preserved by the differential equations. Thus, the differential equation solutions can be classified into homotopy classes.  "
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https://en.wikipedia.org/wiki/Homotopy_class

[Jarek Duda (OP)]

'Inside the neutron'   by Jo van den Brand and Peter de Witt Huberts
https://iopscience.iop.org/article/10.1088/2058-7058/9/2/27/pdf

Thanks for the paper, it indeed also has this positive core, negative shell for neutron - here are some others: https://inspirehep.net/literature/1377841 http://www.phys.utk.edu/neutron-summer-school/lectures/greene.pdf

It also writes "Calculations by  Andrzej  Gorski  of  the  Institute   of  Nuclear Physics  in  Krakow  in  Poland  and  others  using a soliton-type  model" - I am from Krakow, my physics PhD supervisor was from above Institute, but I don't know this professor (24 years ago), nor that they worked on soliton-type models.

Soliton Skyrme-like models of nuclei are now quite popular, e.g. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.232002


But they neglect electric charge, electromagnetism: (ultimately conserved) topological charge is interpreted as baryon number.
We consider models using topological charge as electric charge instead - making that Gauss law counts topological charge (winding number) - building charge quantization into electromagnetism.
For baryons-like solitons there appear local fractional rotation/charge - explaining why proton is lighter than neutron, deuteron than p+n ...

But for verification it needs to be compared with standard view:
- neutron needs this positive core as baryon, which needs to be compensated to zero (negative shell which gives additional energy/mass comparing to proton) - as in these papers,
- in deuteron, neutron needs this charge (e.g. 2/3), so to save energy proton shares part of its charge (~quark-level shift) - leading to observed quadrupole moment.

So generally there is suggestion that quark-level shift of charges is a part of binding mechanism - does it agree with standard view/experiments?
I will read closer tomorrow.

[yor_on]

Sounds reasonable to me Jarek, " We consider models using topological charge as electric charge instead - making that Gauss law counts topological charge (winding number) - building charge quantization into electromagnetism. "

It''s a different way to describe a same experience. I have this view in where I think you can describe a universe differently, still getting to a equivalence. But it's your field of expertise, not mine. Maybe we're like bubbles in a bottle, I don't know. I do like the idea of symmetry breaks though. Do you find any connection from solitons to that?

[Jarek Duda (OP)]

Baryon number is hypothesized to be violated e.g. in baryogenesis or Hawking radiation.
Topological charge is ultimately conserved, also electric - it seems a safer choice, also having Gauss law which has topological analogue (Gauss-Bonnet) ... while there is rather no Gauss law for baryon number (?) as it requires dedicated long-range interaction.

Regarding symmetry braking, we need Higgs-like potential (requiring to break symmetry) to regularize singularities to finite energy - repair the problem of infinite energy of point charge.
If below hedgehog-like configuration would need to use unitary vectors, we would have infinite energy discontinuity in the center - avoided by deformation allowed by potential, intuitively by deforming of electromagnetism into other (weak/strong) interactions.



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