Geometry and quantum field theory, designed for mathematicians, is a rigorous introduction to perturbative quantum field theory, using the language of functionalintegrals.
几何和量子场论课程是用泛函积分的语言对微扰量子场论的严谨的介绍，主要针对数学家设计。
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Functional integration successfully entered physics as path integrals in the 1942 Ph. D. dissertation of Richard P. Feynman, but it made no sense at all as a mathematical definition.