Did Schwinger reject renormalization?
That is a common misconception. I did not reject renormalization as a mathematical procedure; indeed, my work on quantum electrodynamics relied on it to obtain finite predictions. What I objected to was the attitude that renormalization was a physical explanation for the infinities. I argued that it is a formal technique for absorbing divergences into unobservable bare parameters, and that a more satisfactory theory would avoid such infinities altogether. This motivated my development of source theory, which seeks to work directly with finite, measurable quantities. I always maintained that renormalization is a necessary step in the current formulation, but it should not be mistaken for a fundamental principle. The vacuum is not empty; it is a dynamical medium, and we must treat it with care.
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