divergence difficulty

...In quantum field theory, for example, when calculating the mass of an electric charge or an electron, if a higher-order correction is made, the value becomes infinite. This is called the divergence difficulty, and a method to prevent this divergence difficulty was independently devised by Shinichiro Tomonaga, R. Feynman, and J. Schewinger shortly after World War II, called renormalization theory. Classical theory was already facing the divergence difficulty, in which the force that an electron exerts on itself as a point charge becomes infinite, but this difficulty was not fundamentally resolved, and physics moved on to the formation of quantum mechanics and then the construction of relativistic quantum theory. ...

*Some explanations of terms that mention "divergence difficulty" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…場の量子論で，例えば電荷や電子の質量を求める場合，高次の補正を行うとその値が無限大となってしまう。これを発散の困難divergence difficultyといい，発散の困難を防ぐために，第2次世界大戦後まもなく，朝永振一郎，R.ファインマン，J.シェウィンガーによって独立に考案された処法をくりこみ理論という。古典論においてもすでに点電荷としての電子が自分自身に及ぼす力が無限大になってしまうという発散の困難に直面していたが，この困難は本質的な解決をみることなく物理学は量子力学の形成，さらに相対論的量子論の建設へと進んだ。…

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