February 1, 2023

Physicist’s Radical Solution to Century Old Problem of Radiation Reaction – With Controversial Implications

Black Hole-Powered Jet of Electrons and Sub-Atomic Particles Streaming From Centre of Galaxy M87; the blue light is Synchrotron radiation which should produce radiation reaction. Credit: NASA and The Hubble Heritage Team (STScI/AURA).
A Lancaster physicist has proposed a radical solution to the question of how a charged particle, such as an electron, reacted to its own electromagnetic field.
This concern has actually challenged physicists for over 100 years but mathematical physicist Dr. Jonathan Gratus has recommended an alternative technique– released in the Journal of Physics A– with questionable implications.
If a point charge accelerates it produces electro-magnetic radiation, it is well established that. This radiation has both energy and momentum, which need to originate from someplace. It is generally assumed that they originate from the energy and momentum of the charged particle, damping the motion.

The history of attempts to compute this radiation reaction (also understood as radiation damping) date back to Lorentz in 1892. Major contributions were then made by many popular physicists consisting of Plank, Abraham, von Laue, Born, Schott, Pauli, Dirac, and Landau. Active research continues to this day with numerous posts published every year.
The challenge is that according to Maxwells formulas, the electric field at the actual point where the point particle is, is unlimited. The force on that point particle need to also be boundless.
Different approaches have been utilized to renormalize away this infinity. This leads to the well developed Lorentz-Abraham-Dirac equation.
This equation has well known pathological services. A particle following this formula may speed up forever with no external force or accelerate before any force is applied. There is also the quantum version of radiation damping. Ironically, this is among the few phenomena where the quantum version happens at lower energies than the classical one.
This requires colliding really high energy electrons and powerful laser beams, a challenge as the most significant particle accelerators are not positioned near the most powerful lasers. Existing results reveal that quantum radiation response does exist.
The alternative approach is to consider lots of charged particles, where each particle reacts to the fields of all the other charged particles, but not itself. This technique was hitherto dismissed, given that it was assumed that this would not save energy and momentum.
Dr Gratus reveals that this assumption is incorrect, with the energy and momentum of one particles radiation coming from the external fields used to accelerate it.
We might for that reason think about the discovery of quantum radiation reaction as similar to the discovery of Pluto, which was found following forecasts based on discrepancies in the motion of Neptune. Radiation response was forecasted, found and then revealed not to be needed.”.
Reference: “Maxwell– Lorentz without self-interactions: conservation of energy and momentum” by Jonathan Gratus, 21 January 2022, Journal of Physics A Mathematical and Theoretical.DOI: 10.1088/ 1751-8121/ ac48ee.

The history of attempts to calculate this radiation reaction (also known as radiation damping) date back to Lorentz in 1892. Existing outcomes reveal that quantum radiation reaction does exist.
He stated: “The controversial implications of this outcome is that there need not be classical radiation response at all. We might for that reason think about the discovery of quantum radiation response as similar to the discovery of Pluto, which was discovered following forecasts based on inconsistencies in the movement of Neptune. Radiation reaction was predicted, discovered and then shown not to be needed.”.

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