Gauge Transformation Quantum Electrodynamics

In summary, the conversation discusses the use of different gauges when studying particles in the presence of an electromagnetic field. It is well known that the Hamiltonian can be expressed using a specific gauge, and the only condition for the gauge is that the curl of the vector potential equals the magnetic field. The question is whether this condition can be relaxed and if two different gauges can be selected. The speaker has explored this possibility and found that it does not make a difference in the equations of motion for the particles. They are particularly interested in the quantum problem and whether fixing two different gauges would affect the symmetry of the Hamiltonian.
  • #1
Juan Carlos
22
0
It's well known when if we are working on problems related to particles in presence of an electromanetic field, the way we state the problem can be done using the next Hamiltonian:
[itex]H=\dfrac{(p-\frac{e}{c}A)^2}{2m} +e \phi[/itex] where the only condition for A is: [itex]\vec{\nabla } \times \vec{A} =\vec{B}[/itex]
So we have this "gauge freedom" under (of course) the above condition .
What happens when are studying two or more partcles in presence of the electromagnetic field.

Naturally:
[itex]H=\dfrac{(p_{1}-\frac{e}{c}A)^2}{2m} +\dfrac{(p_{2}-\frac{e}{c}A)^2}{2m} +e \phi[/itex] where the only condition for A is: [itex]\vec{\nabla } \times \vec{A} =\vec{B}[/itex]

The question is: can we relax the condition of one unique gauge for all the particles?

Just saying:
can we select two different gauges? obviously with the condition : [itex]\vec{\nabla } \times \vec{A} =\vec{B}[/itex]

I've been working on this, I satetd two different gauges and I can say that there is no difference in terms between the equations of motion having the same gauge. (Hamilton)

In particular I've done the same for the correspoding quantum problem obtainig the heisemberg equations, having the same result: no difference.

I'm interested on the quantum problem because having two different gauges could provoque loosing the symmetry of a Hamiltonian given.
 
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  • #2
When you fix a gauge you do that for the electromagnetic potential, which is only one in your problem. This shouldn't be influenced by how many particles you have. What do you mean by fixing two different gauges?
 

FAQ: Gauge Transformation Quantum Electrodynamics

What is gauge transformation in quantum electrodynamics?

Gauge transformation is a mathematical concept used in quantum electrodynamics to describe the change in the electromagnetic potential of a system without affecting the physical observables. It involves transforming the equations of the system by adding or subtracting a constant value to the potential.

Why is gauge transformation important in quantum electrodynamics?

Gauge transformation is important because it allows us to describe the same physical system using different mathematical representations. This can simplify calculations and provide a deeper understanding of the underlying physics.

What is the significance of gauge invariance in quantum electrodynamics?

Gauge invariance is a fundamental principle in quantum electrodynamics, stating that the laws of physics should remain unchanged under gauge transformations. This is crucial for maintaining the consistency and accuracy of the theory.

How does gauge transformation affect the quantization of electromagnetic fields?

Gauge transformation plays a crucial role in the quantization of electromagnetic fields. It allows us to choose a specific gauge, such as the Coulomb gauge, to simplify the equations and make the quantization process more manageable.

Can you give an example of gauge transformation in quantum electrodynamics?

One example of gauge transformation in quantum electrodynamics is the transformation of the electric and magnetic fields when switching from the Lorenz gauge to the Coulomb gauge. This transformation does not change the physical observables, but it simplifies the equations and makes calculations easier.

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