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This question is brief and simple. As a layman, it is my understanding that QCD (Quantum Chromodynamics) explains the nuclear force as a "residual" force, mediated by pions (mesons), which pinch off as "virtual" pairs of quarks from the protons and neutrons. In terms of pions being responsible for the residual nuclear force, how does one fit nuclear fission into the picture? Is the energy from the splitting of, say, a uranium isotope coming from the release of pions or something? When "binding energy", generated by pion exchange, is released, what is happening on the quark level, or on the level of QCD? Any info or reference is appreciated.

EDIT: This question has been resolved, because I've found Nuclear effective field theory: Status and perspectives. I never heard of nuclear EFT or "ab initio nuclear physics," it is not something you come across in standard reading, but this is precisely what I was looking for. Also, Microscopic Theory of Nuclear Fission (PDF).

GrapefruitIsAwesome
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muldrowhanif
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  • I agree with Zachos answer. I had tried answering your "layman" question, a draft was still open, because I was stuck how to simplify complicated concepts. The papers you site are just theoretical models that can have no check with experiment, as physics models should. I have this simple analogy: If you throw a ball on a wall, do you need all the details of the electromagnetic binding of its atoms and molecules to calculate its trajectory? At most the elasticity of the ball might help for accurate details, a statistical effect of the underlying electromagnetic bindings. – anna v Feb 23 '23 at 05:13

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Brief and simple question with no brief and simple answer.

Pion exchange is not alone in explaining the nuclear effective potential, and especially its repulsive core. How QCD connects to standard nuclear physics with characteristic/binding energies of about 8MeV, two orders of magnitude below the QCD confinement scale is a tricky and recondite issue, and, for all practical purposes, sheds very little crucial light in the type of nuclear forces and energy release involved in nuclear fission.

So my first instinct is to discourage you from finding good explanations of fission in QCD; one had best accept conventional nuclear physics, systematics and potentials, etc, to understand fission, before resorting to much, much higher energy QCD to connect the foundations of such nuclear physics to it. It is an academic, still confused area which no simplistic popular science "story" can serve to illuminate.

Cosmas Zachos
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  • How strange. Thank you for the reply. So, maybe I'm just misunderstanding fission. After all, I haven't been to school for physics, I just like reading articles. Is it then enough to say that the energy released in a nuclear fission reaction is simply the "after-effect" of the sudden massive repulsion of the nuclei through their electromagnetic forces, as if like a snapping rubber band? Is energy then just an illusion of momentum or kinetic motion possessed by charged particles acting according to their forces? – muldrowhanif Feb 22 '23 at 23:19
  • What you are asking has little to do with quarks and QCD, but, instead, with standard nuclear physics. Indeed, once an initial small triggering/destabilizing energy has been provided, a Uranium nucleus (unstable) splits into two daughter nuclei more tightly bound, with the release of 200MeV (still below QCD energies, coincidentally), due to the now relaxed electromagnetic "pressure"... – Cosmas Zachos Feb 22 '23 at 23:27
  • Could you link me to any specialized nuclear physics textbooks you think are really rigorous? I assume you know some materials. Wikipedia articles are lacking in rigorous explanation. I'd like to see the math. I also hope physicists can unify QCD with the bigger-picture phenomena someday, if not myself. – muldrowhanif Feb 22 '23 at 23:32
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    You started out by bypassing rigor, and now you are asking for it? The sources of this, standard nuclear physics, might answer some of your questions... You might find some you like among them? – Cosmas Zachos Feb 22 '23 at 23:42
  • Here is something, and here is a popular science movie... – Cosmas Zachos Feb 22 '23 at 23:51
  • I feel some kind of superiority complex is going on here. If you felt the question contained no merit, you shouldn't have answered it. The logic behind asking it was that, if one claims to possess a fundamental model (QCD), that it should extend to all "higher" phenomena. The reason it was asked in non-rigorous terms was because the understandings going into it come from non-rigorous material. I came here seeking better material. Just because one is unfamiliar with convention or is conflating different concepts with each other, does not mean there was no merit behind the intent. – muldrowhanif Feb 23 '23 at 00:28
  • Logically, it follows that if a neutron is a collection of quarks, it is doing something on the quark-level when it "slams" into a nucleus to disrupt the strong interaction between its constituent nucleons. By some miracle, I've managed to find this: https://www.frontiersin.org/articles/10.3389/fphy.2023.1129094/full It turns out, what I have been seeking is what is termed "ab initio nuclear physics." There is no need for further replies. Have a good one. – muldrowhanif Feb 23 '23 at 00:31
  • My "recondite issue" link is ab initio nuclear physics. But your expectation that quarks provide insight to fission beyond through shaping the nuclear potential was adequately put to rest, the primary focus of the answer. – Cosmas Zachos Feb 23 '23 at 00:47
  • Let us continue this discussion in chat. – muldrowhanif Feb 23 '23 at 01:14