完成爱因斯坦的理论——粒子物理学的突破

在它首次出现一个多世纪后，科学家们完成了爱因斯坦关于电磁学狭义相对论的功课。

大阪大学的研究人员已经证明了由快速移动的带电粒子产生的电场的相对论收缩，正如爱因斯坦的理论所预测的那样，这可能有助于改进粒子和辐射物理学研究。

一个多世纪以前，最著名的现代物理学家之一阿尔伯特·爱因斯坦提出了开创性的狭义相对论。 我们所知道的关于宇宙的大部分事情都是基于这个理论，然而，其中的一部分还没有被实验证明。 学者谁 大阪大学 激光工程研究所首次使用超快光电测量可视化了以接近光速行进的电子束周围电场的收缩，并展示了产生过程。

根据爱因斯坦的狭义相对论，必须使用将空间和时间坐标相加的“洛伦兹变换”，才能准确描述以接近光速的速度经过观察者的物体的运动。 他能够解释这些变换如何导致电场和磁场的自洽方程。

虽然相对论的各种效应已经通过非常高程度的实验被多次证明[{” attribute=””>accuracy, there are still parts of relativity that have yet to be revealed in experiments. Ironically, one of these is the contraction of the electric field, which is represented as a special relativity phenomenon in electromagnetism.

Illustration of the formation process of the planar electric field contraction that accompanies the propagation of a near-light-speed electron beam (shown as an ellipse in the figure). Credit: Masato Ota, Makoto Nakajima

Now, the research team at Osaka University has demonstrated this effect experimentally for the first time. They accomplished this feat by measuring the profile of the Coulomb field in space and time around a high-energy electron beam generated by a linear particle accelerator. Using ultrafast electro-optic sampling, they were able to record the electric field with extremely high temporal resolution.

It has been reported that the Lorentz transformations of time and space as well as those of energy and momentum were demonstrated by time dilation experiments and rest mass energy experiments, respectively. Here, the team looked at a similar relativistic effect called electric-field contraction, which corresponds to the Lorentz transformation of electromagnetic potentials.

“We visualized the contraction of an electric field around an electron beam propagating close to the speed of light,” says Professor Makoto Nakajima, the project leader. In addition, the team observed the process of electric-field contraction right after the electron beam passed through a metal boundary.

When developing the theory of relativity, it is said that Einstein used thought experiments to imagine what it would be like to ride on a wave of light. “There is something poetic about demonstrating the relativistic effect of electric fields more than 100 years after Einstein predicted it,” says Professor Nakajima. “Electric fields were a crucial element in the formation of the theory of relativity in the first place.”

This research, with observations matching closely to Einstein’s predictions of special relativity in electromagnetism, can serve as a platform for measurements of energetic particle beams and other experiments in high-energy physics.

Reference: “Ultrafast visualization of an electric field under the Lorentz transformation” by Masato Ota, Koichi Kan, Soichiro Komada, Youwei Wang, Verdad C. Agulto, Valynn Katrine Mag-usara, Yasunobu Arikawa, Makoto R. Asakawa, Youichi Sakawa, Tatsunosuke Matsui and Makoto Nakajima, 20 October 2022, Nature Physics.
DOI: 10.1038/s41567-022-01767-w

The study was funded by the Japan Society for the Promotion of Science and the NIFS Collaborative Research Program.