眼见着又到了一年开学季。从寒假（哦，现在只能叫春节假期了）拖到五一拖到毕业再拖到开学，终于还是抽出时间把这篇文章憋了出来。

事情当然要从「双十一」开始说起。想不到打折力度最大的既不是天猫，也不是京东，而是国家卫健委。随后的一个月在动荡中度过，场面堪比阿根廷对法国的那场决赛。政策来回拉扯，作为普通人唯有随波逐流。12 月 7 日又出「新十条」，放开的局面便再也收不住了。

欧拉计划 71–80 题。

欧拉计划 61–70 题。

Tensor networks provide a general framework to describe many interesting and important concepts in condensed matter physics and quantum information theory, such as topological orders, entanglement, and even holographic duality.

Category theory formalizes many mathematical structures, especially the mapping between “objects”. A modular tensor category is a category with some extra structures and can provide a mathematical foundation for some physical concepts, especially the topological orders.

欧拉计划 51–60 题。

欧拉计划 41–50 题。

欧拉计划 31–40 题。

欧拉计划 21–30 题。