The closed loop integral of the whole Amperian rectangle equals the sum of the integrals for each of the sides of the rectangle.
整个安培矩形的闭环积分等于矩形每条边的积分之和。
英语百科
Loop integral
In quantum field theory and statistical mechanics, loop integrals are the integrals which appear when evaluating the Feynman diagrams with one or more loops by integrating over the internal momenta.
There are two standard techniques for evaluating loop integrals: