How exactly does Quantum Field Theory explain atomic structures? As I understand it oscillations in the quark fields are "held together" by other oscillations of the baryon matter field to form protons and neutrons (baryons, a type of hadrons), which are themselves held in a nucleus by oscillations of the strong force field? How are electron field oscillations held to the nuclei. Is it by the electro-magnetic force field, the weak force field, or the lepton matter field?

Follow up: Thank you very much for the answers, ladies/gentlemen. I realize that QFT isn't needed to explain atomic structure. It's just that I only recently became aware of QFT and I am absolutely fascinated by it. As a 29 year old electrical engineer I could never look the same way as I did until now at the field I've been working in my whole life. Please excuse me if my question isn't correctly formulated. Basically I want to know if my first statement about the nucleus is true according to QFT. And also what exactly holds the electrons "in orbit" around the nucleus. If it is the electromagnetic force then why electrons don't completely collide with the positively charged nucleus. Additionally as far as I know the weak force cannot produce bound states so what exactly is its role. If the weak force acts on the flavor of quarks and leptons and there is a separate field for each lepton and quark then what role if any plays the lepton matter field in holding an electron field oscillation (a lepton) in orbit around a nucleus. Are the separate lepton fields different entities from the lepton matter field??? I have Dr. Rodney Brooks' book 'Fields of Color' but I cannot find exact answers there. I also have professor Anthony Zee's book 'Quantum Field Theory in a Nutshell' and a few others, but I just don't have the possibility to spend as much time delving in these books as I'd like, so I'm hoping to get answers a little quicker in forums.

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    $\begingroup$ Since you only need ordinary quantum mechanics (QM) to (mostly) explain atomic structures, you only need to show that quantum field theory (QFT) reduces to QM in appropriate limit. Is your question about how to show it? $\endgroup$
    – Danijel
    Apr 21, 2017 at 10:49

1 Answer 1


You don't need QFT to explain atomic structure. Normal quantum mechanics is sufficient to explain the electronic structure of an atom, which uses a Coulomb potential ie electromagnetic interaction. For small atoms, the non-relativistic Schroedinger equation suffices, but for larger atoms the Dirac equation is needed (the relativistic version). Relativistic effects can explain the colour of gold and the phase of mercury at room temperature.

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    $\begingroup$ While this is true, it doesn't really answer the question of how QFT explains the atomic structure. $\endgroup$
    – Fingolfin
    Apr 21, 2017 at 17:00
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    $\begingroup$ @Fingolfin Like the answer to "how does QFT explain the structure of the Sun?", if the answer is "it doesn't, you use an effective theory instead" then that's what you say and you leave it there. This answer is right on the dot. $\endgroup$ Apr 21, 2017 at 17:29
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    $\begingroup$ More specifically. QFT reduces to non relativistic QM (Scheodinger's equation) when speeds are significantly less than c. For the heavy atoms the speeds can get bigger and you still don't need QFT because the energies are small enough that new particles can not be created and then it reduces to the Dirac equation. Those 'reductions to' are part of the reason that when QFT or Diracs equations were figured out they made sure it corresponded to those in the appropriate limits. Same for QM reducing to classical mechanics for large enough systems. In physics each new equation builds on the previous $\endgroup$
    – Bob Bee
    Apr 21, 2017 at 18:20

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