アインシュタインの理論完成 – 粒子物理学の突破口

大阪大学の研究者らは、アインシュタインの理論で予測したように、急速に動く荷電粒子によって生成された電場の相対論的収縮を示し、放射線および粒子物理学の研究を改善するのに役立ちます。

1世紀前、最も有名な現代物理学者の一人であるアルバート・アインシュタインは、画期的な特殊相対性理論を提案しました。 私たちが宇宙について知っているほとんどのものはこの理論に基づいていますが、そのいくつかはこれまで実験的に証明されていません。 出身科学者 大阪大学 レーザー工学研究所は、光の速度に近い速度で移動する電子ビームを取り巻く電場の収縮を可視化し、生成プロセスを実証するために、超高速電気光学測定を初めて利用した。

アインシュタインの特別な相対性理論によれば、光の速度に近い速度で観察者を通過する物体の動きを正確に記述するには、空間と時間座標を組み合わせた「ローレンツ変換」を使用する必要があります。 彼は、これらの変換が電場と磁場の一貫した方程式にどのように帰結したかを説明できました。

相対性理論の他の効果は、非常に高いレベルの実験によって何度も実証されているが、[{” 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.