# QED Feynman (coupling number called j)

• eb227
In summary, on page 92 (Figure 58) of his book, Feynman explains that the amplitude for a coupling, which he calls j, is approximately negative .1 for the electron. This number is also referred to as the "charge" and is represented by e^2=1/137 in what is known as "natural units" in QED. If units are to be included, e^2/(hbar c)=1/137 can be used, or even 1/fourpiepsilonzero.
eb227
On page 92 (Figure 58) Feynman states:
"The amplitude for a coupling is a number that I will call j; it is about
negative .1 for the electron (this number is sometimes called the "charge").
Charge?? I don't get it.
Would appreciate an explanation?

eb227 said:
On page 92 (Figure 58) Feynman states:
"The amplitude for a coupling is a number that I will call j; it is about
negative .1 for the electron (this number is sometimes called the "charge").
Charge?? I don't get it.
Would appreciate an explanation?
In what is called "natural units" in QED, the charge on the electron is given by e^2=1/137, so e would be about .1.
If you want to put in units, you would have e^2/(hbar c)=1/137.
You could even put in 1/fourpiepsilonzero if you want.

QED (Quantum Electrodynamics) is a theory that explains the interactions between electrically charged particles, such as electrons. In this context, the term "coupling" refers to the strength of the interaction between two particles. The coupling number, j, is a numerical value that represents this strength.

On page 92 of his book, "The Feynman Lectures on Physics," Richard Feynman explains that the amplitude (or probability) for a coupling is approximately equal to -0.1 for an electron. This value is often referred to as the "charge" of the electron.

To understand this further, it is important to note that in QED, particles interact by exchanging tiny particles called photons. These photons carry the electromagnetic force, which is responsible for the interactions between charged particles. The strength of this force is determined by the charge of the particles involved.

In the case of an electron, it has a negative charge, which means it repels other negatively charged particles and is attracted to positively charged particles. The value of -0.1 for the coupling number, or charge, of an electron indicates the strength of this interaction.

In summary, Feynman is using the term "charge" to refer to the coupling number, which represents the strength of the electromagnetic interaction between particles in QED. It is a fundamental concept in understanding the behavior of charged particles and their interactions.

## 1. What is QED Feynman and what does it stand for?

QED Feynman is a mathematical framework that describes the behavior of electrons, positrons, and photons. It stands for Quantum Electrodynamics Feynman, named after physicist Richard Feynman who helped develop it.

## 2. What is the coupling number called j in QED Feynman?

In QED Feynman, the coupling number called j represents the strength of the interaction between an electron and a photon. It is a dimensionless constant that can change depending on the energy scale of the particles involved.

## 3. How is QED Feynman used in particle physics?

QED Feynman is used in particle physics to predict the behavior and interactions of subatomic particles. It is one of the most successful and accurate theories in physics, and has been used to make precise calculations for experiments at particle accelerators such as the Large Hadron Collider.

## 4. What is the significance of the coupling number j in QED Feynman?

The coupling number j in QED Feynman is significant because it determines the strength of the electromagnetic force between particles. A higher value of j means a stronger interaction, while a lower value means a weaker interaction. This constant is crucial for understanding the behavior of particles and how they interact with each other.

## 5. Can QED Feynman be applied to other fields of physics?

QED Feynman is primarily used in particle physics, but it has also been successfully applied to other fields such as condensed matter physics and atomic physics. It is a fundamental part of the Standard Model of particle physics, and its principles and calculations can be extended to other areas of physics to help understand and predict the behavior of different systems.

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