What types of forces are described in the standard minimal QED Lagrangian?

In summary, the magnetic part of the Lorentz Force in Q.E.D. is realized through the absorption and emission of virtual photons, similar to the electrical part. However, in the Q.E.D. world, force is not a fundamental concept and the distinction between electric and magnetic components of the electromagnetic field is not necessary. The relativistic description of electrodynamics eliminates this artificial split and includes all forces, including those related to the magnetic moment of the electron, in one Lagrangian.
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LarryS
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How is the magnetic part of the Lorentz Force realized in Q.E.D. via photon exchange, etc.?
In Q.E.D., the electrical part of the Lorentz Force between unlike and like charged particles is realized through the absorption and emission of photons.

How is the magnetic part of the Lorentz Force realized in Q.E.D. via photon activity?

As always, thanks in advance.
 
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referframe said:
In Q.E.D., the electrical part of the Lorentz Force between unlike and like charged particles is realized through the absorption and emission of photons.

How is the magnetic part of the Lorentz Force realized in Q.E.D. via photon activity?
Um, by absorption and emission of (virtual) photons?

Why do you think that is not a sufficient explanation for the magnetic part but it is for the electric part? What's the difference?
 
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The Lorentz Force is basically Classical EM, right? In that world, the magnetic force has a velocity dependence. Is that velocity dependence in the Q.E.D. world still represented somehow, or is Q.E.D. only concerned with the net force on the particle?
 
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referframe said:
Is that velocity dependence in the Q.E.D. world still represented somehow, or is Q.E.D. only concerned with the net force on the particle?
"Force" isn't really a thing in QM. And this sentance seems to assume some dichotomy that isn't really there.
 
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Not sure which dichotomy you're referring to. Electrical vs Magnetic?
 
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referframe said:
Not sure which dichotomy you're referring to.
The one you posted and I quoted.
 
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The elegance of the relativistic description of electrodynamics (no matter whether classical or quantum) is that you don't need the artificial split of the electromagnetic field in electric and magnetic components anymore although this is of course important to understand the phenomenology, but the split indeed is frame dependent.

Writing down the standard minimal QED Lagrangian, i.e., a Dirac field minimally coupled to the em. field, contains all kinds of "forces", i.e., the standard Lorentz force ##q \vec{E}+q \vec{v} \times \vec{B}/c## as well as the "forces" due to the magnetic moment of the electron.

By chance we have a more formal answer in another recent thread:

https://www.physicsforums.com/threads/samalkhaiats-challenge-002.1006325/
 
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FAQ: What types of forces are described in the standard minimal QED Lagrangian?

What is the Lorentz Force in Q.E.D.?

The Lorentz Force in Q.E.D. is a fundamental force in quantum electrodynamics (Q.E.D.) that describes the interaction between electric and magnetic fields with charged particles. It is named after Dutch physicist Hendrik Lorentz, who first described the force in the late 19th century.

How does the Lorentz Force in Q.E.D. differ from classical electromagnetism?

In classical electromagnetism, the Lorentz Force is described by the equation F = q(E + v x B), where q is the charge of the particle, E is the electric field, v is the velocity of the particle, and B is the magnetic field. In Q.E.D., the Lorentz Force is described by a more complex equation that takes into account quantum effects and interactions with virtual particles.

What is the role of the Lorentz Force in Q.E.D. in particle interactions?

The Lorentz Force in Q.E.D. plays a crucial role in particle interactions, as it describes how charged particles interact with each other and with electromagnetic fields. This force is responsible for many phenomena, such as the scattering of particles, the deflection of particles in a magnetic field, and the creation and annihilation of particles and antiparticles.

Can the Lorentz Force in Q.E.D. be unified with other fundamental forces?

Currently, the Lorentz Force in Q.E.D. is not unified with the other fundamental forces, such as the strong and weak nuclear forces and gravity. However, there have been attempts to unify these forces through theories such as string theory and quantum field theory. These theories aim to describe all the fundamental forces in a single framework.

What are the practical applications of the Lorentz Force in Q.E.D.?

The Lorentz Force in Q.E.D. has many practical applications, such as in particle accelerators, where it is used to accelerate and manipulate particles. It is also used in medical imaging techniques, such as magnetic resonance imaging (MRI), which rely on the interaction between magnetic fields and charged particles in the body. Additionally, the Lorentz Force is used in various technologies, such as particle detectors and magnetic levitation systems.

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