【教程】function analysis
本帖最后由 厚积薄发 于 2010-1-26 21:12 编辑In mathematics, a functional is traditionally a map from a vector space to the field underlying the vector space, which is usually the real numbers. In other words, it is a function that takes a vector as its argument or input and returns a scalar. Its use goes back to the calculus of variations where one searches for a function which minimizes a certain functional. A particularly important application in physics is to search for a state of a system which minimizes the energy functional.
In functional analysis, the functional is also used in a broader sense as a mapping from an arbitrary vector space into the underlying scalar field (usually, real or complex numbers). A special kind of such functionals, linear functionals, gives rise to the study of dual spaces.
Transformations of functions is a somewhat more general concept, see operator. good boy,thanks a lot 居然是word版的，很少见啊，就是楼主没有说清楚是谁写的，不然就更好了 谢谢!!!!!!!加油！！！！！！！！
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