Little in mathematics beyond the elementary level of calculus of variations, and nothing at all about Banach algebra or Riemannian manifolds.
对基础变分微积分以外的数学领域所知不多,完全不懂巴拿赫代数或黎曼流形。
英语百科
Banach algebra
In mathematics, especially functional analysis, a Banach algebra, named after Stefan Banach, is an associative algebra A over the real or complex numbers (or over a non-Archimedean complete normed field) that at the same time is also a Banach space, i.e. normed and complete. The algebra multiplication and the Banach space norm are required to be related by the following inequality: