Understanding Electrons: The Difference Between QFT and QED

Click For Summary

Discussion Overview

The discussion revolves around the differences between Quantum Field Theory (QFT) and Quantum Electrodynamics (QED), specifically focusing on the nature of electrons within these frameworks. Participants explore theoretical concepts and interpretations related to the classification of electrons as field quanta or particles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that QED is a specific type of QFT, while QFT serves as a broader framework for modeling quantum phenomena.
  • There is a suggestion that QFT encompasses various gauge theories, although some participants express uncertainty about this claim.
  • Participants discuss whether electrons in QED are considered field quanta, with some affirming that they are excitations of the electron field.
  • Questions arise regarding Feynman's characterization of electrons as particles rather than field quanta, leading to further exploration of definitions and interpretations.
  • It is noted that in QED, the electron is viewed as an excitation of the electron field, while photons are excitations of the electromagnetic field.
  • A later reply references Feynman's evolving perspective on the field viewpoint, suggesting a historical context to the discussion.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement, particularly regarding the definitions and interpretations of electrons in QFT and QED. No consensus is reached on the implications of Feynman's statements about particles and field quanta.

Contextual Notes

Some claims depend on specific interpretations of quantum field theory and may involve unresolved assumptions about the nature of particles and fields. The discussion reflects varying levels of understanding and differing viewpoints on the relationship between QFT and QED.

Philipsmett
Messages
78
Reaction score
4
What different between QFT and QED? In QFT electron is field quanta, what is electron in QED?
 
Physics news on Phys.org
QED is a type of quantum field theory. QFT is just a way of modeling quantum phenomenon and doesn't necessarily refer to a specific model. I believe there are several gauge theories that are also quantum field theories, but I could be mistaken.
 
  • Like
Likes   Reactions: Philipsmett
Yes, QED (for electromagnetic interactions) is an example of a QFT. Other examples of QFTs are quantum chromodynamics (QCD) for the strong interaction, and electroweak theory, sometimes called quantum flavordynamics (QFD) for the unified electromagnetic and weak interactions.
 
  • Like
Likes   Reactions: Philipsmett
Drakkith said:
QED is a type of quantum field theory. QFT is just a way of modeling quantum phenomenon and doesn't necessarily refer to a specific model. I believe there are several gauge theories that are also quantum field theories, but I could be mistaken.
What is electron in QED? Is it field quanta?
 
Philipsmett said:
What is electron in QED? Is it field quanta?

QED is a QFT, so an electron in QED is whatever it is in QFT. And you already said what it is in QFT in your first post.
 
  • Like
Likes   Reactions: Philipsmett
PeterDonis said:
QED is a QFT, so an electron in QED is whatever it is in QFT. And you already said what it is in QFT in your first post.
Why did Feynman say that the electron is a particle and not a field quanta?
 
Philipsmett said:
Why did Feynman say that the electron is a particle and not a field quanta?

A particle is a field quantum.
 
PeterDonis said:
A particle is a field quantum.
that is, the electron in QED is the excitation in the field?
 
Yes, it's the excitation of electron field. Excitations of electromagnetic fields are photons. Maybe what he meant is that electrons are not exscitations of electromagnetic field.
 
  • #10
Philipsmett said:
the electron in QED is the excitation in the field?

It's an excitation of the electron field. As @weirdoguy said. QED contains two fields, the electron field and the electromagnetic field. Photons are excitations of the electromagnetic field.
 
  • #11
FYI, Feynman came over to the field viewpoint later in life - see reference in Julian Schwinger's Climbing the Mountain.
 

Similar threads

Graduate Two-electron Lagrangian in QED
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad QED Picture of static EM Fields
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Confusion about Scattering in Quantum Electrodynamics
  • · Replies 134 ·
5
Replies
134
Views
12K
Graduate QED Formulation with Massive Photon Fields
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad QED & In-Ground Electrons: Why No Photon Emission?
  • · Replies 9 ·
Replies
9
Views
2K
Graduate QED Bound States: Weinberg's Explanation & Breakdown
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Can we create a random variable using QED effects?
  • · Replies 25 ·
Replies
25
Views
3K
Graduate What is the quantum picture of laser field accelerating free electrons?
  • · Replies 6 ·
Replies
6
Views
2K
Graduate How can we derive the results that we know about QM from QED?
  • · Replies 22 ·
Replies
22
Views
4K
Undergrad One vertex interactions in QED - error in the book?
  • · Replies 4 ·
Replies
4
Views
2K