Einstein's summation convention

例句：

1. 1. Inphysics, the Einstein summation convention is used to simplify calculations by summing over all possible values of a variable.
   在物理学中，爱因斯坦求和规则被用来简化计算，通过对所有可能的值的变量进行求和。
2. 2. The Einstein summation convention is widely used in engineering and science to avoid complex mathematical expressions.
   爱因斯坦求和规则在工程和科学领域广泛使用，以避免复杂的数学表达式。
3. 3. The Einstein summation convention is also known as the Einstein summation rule, which is a fundamental principle in the study of quantum mechanics.
   爱因斯坦求和规则也被称为爱因斯坦求和规则，是量子力学研究中的一个基本原则。