Black body radiation and ultraviolet catastrophe: the error at the origin of quantum mechanics

News date: 
Thursday, May 26, 2022
Prof. Wang, Prof. Casati e Prof. Benenti

Blackbody radiation and ultraviolet catastrophe: a historical error at the origins of quantum mechanics. This is the topic addressed by Giulio Casati, Emeritus professor of Physics at Insubria University, with Jiao Wang of Xiamen University and Giuliano Benenti of the National Institute of Nuclear Physics, in an article published in Physical Review Letters.
A very complex scientific topic that Professor Casati explains in the summary that we propose below.
In his famous «Lectures on Physics», volume 1, Richard Feynman writes: «Thus was the classical theory absolutely incapable of correctly describing the distribution of light from a blackbody, just as it was incapable of correctly describing the specific heats of gases. Physicists went back and forth over this derivation from many different points of view, and there is no escape. This is the prediction of classical physics ... is called Rayleigh's law, ... and is obviously absurd ".
This statement by Feynman about a central problem in the history of quantum physics, which represents one of the greatest revolutions of humanity, is incorrect. In fact, as shown in the article published in Physical Review Letters, the Rayleigh-Jeans law, which leads to the so-called ultraviolet catastrophe, that is, the absurd effect of the emission of electromagnetic radiation with infinite power, is not a consequence of classical mechanics. It is instead a consequence of the hypothesis of equipartition of the energy between the various degrees of freedom. This hypothesis, historically considered plausible, has no justification for which the exact solution of the equations of motion is necessary. In our work we show that a correct treatment of the classical equations does not lead to any absurd result and in particular it does not lead to the Rayleigh-Jeans law. On the contrary, it is compatible with the Stefan-Boltzmann law, which is known to be in full agreement with the experimental results.
Our results therefore require a critical reconsideration of the role of classical physics for the understanding of quantum mechanics.

(Picture: from left: Jiao Wang, Giulio Casati and Giuliano Benenti)

Last modified: Thursday, May 26, 2022 - 12:03