Runaway Solution in QED: A Discussion with Lorenzo

In summary, the conversation discussed the existence of a "Runaway solution" in classical electromagnetism and how it relates to quantum electrodynamics (QED). The question of whether QED solves this problem or if it still remains was raised, and the possibility of renormalization eliminating the issue was also mentioned. However, it was acknowledged that our current knowledge of QED is limited to a series in powers of the electron charge and it is uncertain if a non-perturbative solution would reveal any further information.
  • #1
Sleuth
47
4
HI everybody.
I'm here with a question that I would like to discuss with you.
As you all probably know better than I do, in classical electromagnetism there exists the so called "Runaway solution", i.e. the auto-acceleration of a charged particle.

It is not clear to me how this problem can be seen in QED, and generally speaking in a quantum theory, if it is solved, and if it is not solved.

If i remember well, the runaway solution should be due to the interaction of a charged particle with its e.m. field. But isn't this already included in the "self-energy" of the electron?

and if yes, can we say that renormalization eliminates completely the problem, namely that the inconsistency is cured?

Bye,
Lorenzo
 
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  • #2
I don't think our knowledge of QED has changed in the past 35 years, so here's a quote from a http://books.google.com/books?id=lS...resnum=3&ved=0CCUQ6AEwAg#v=onepage&q&f=false" which deals with this exact issue:
"How does the same problem look in quantum theory? We do not know [...] But we have never yet succeeded in extracting any information from quantum field theory except in terms of a series in powers of the electron charge. But the problem to which we have been led in the classical case disappears as soon as one expands in a power series. It occurs only in a non-perturbative solution. The question whether the limit implied by the infinite renormalization of quantum electrodynamics would show similar difficulties for a non-perturbative solution, must remain open."
 
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1. What is the runaway solution in QED?

The runaway solution in QED (Quantum Electrodynamics) is a theoretical phenomenon that occurs in the theory of quantum electrodynamics. It refers to the behavior of charged particles in the presence of an external electromagnetic field. In this scenario, the particles experience an infinite acceleration and emit an infinite amount of energy, which is not physically possible.

2. How was the runaway solution discovered?

The runaway solution was first discovered by physicist Freeman Dyson in 1949 while working on the quantum electrodynamics theory. He noticed that the equations predicted an unphysical behavior of charged particles in the presence of an external electromagnetic field.

3. What is the significance of the runaway solution in QED?

The runaway solution is an important concept in QED as it highlights the limitations of the theory and the need for further developments. It also plays a role in understanding the behavior of particles in extreme conditions, such as in the presence of strong electromagnetic fields.

4. How is the runaway solution prevented in QED calculations?

In order to prevent the occurrence of the runaway solution in QED calculations, physicists use a technique called "renormalization." This involves making small adjustments to the equations to account for the infinite values predicted by the runaway solution, resulting in finite and physically meaningful results.

5. What implications does the runaway solution have for the field of physics?

The runaway solution has significant implications for the field of physics as it highlights the need for a more comprehensive theory that can accurately describe the behavior of particles in extreme conditions. It has also led to further developments in the field of quantum field theory, which aims to reconcile the theories of quantum mechanics and special relativity.

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