Dirac-type problems for hypergraphs

虽然组合数学和人类的计算能力一样古老，但它最令人印象深刻的增长是在最近几十年才看到的，主要是由于计算机科学的快速发展。极值组合学研究在一类有限对象上求函数的最大值或最小值的问题。这类问题通常与数学的其他分支和其他科学领域有关，包括生物、化学、计算机科学、信息和编码理论。提出的研究集中在超图的极值问题上。由于超图具有比图更复杂的结构，将结果从图推广到超图通常并不简单，而且经常会产生新的现象。例如，有多种方法(取决于如何定义超图中的度和圈)将狄拉克关于哈密尔顿圈的经典结果推广到超图--没有一种方法有简单的证明。狄拉克问题以及相关的匹配和包装问题最近受到了相当大的关注。现代工具，如吸收方法和规则方法，帮助产生了新的结果，但该领域的许多根本问题仍未解决。PI计划解决该领域的许多突出问题，发展超图的极值理论。

Although Combinatorics is as old as human's ability to count, its most impressive growth has been seen only in recent decades, mainly due to the rapid development of computer science. Extremal Combinatorics deals with the problems of finding the maximum or minimum value of a function over a class of finite objects. Such problems are often related to other branches of mathematics and other fields of science, including biology, chemistry, computer science, information and coding theory. The proposed research concentrates on extremal problems for hypergraphs. Since hypergraphs have more complicated structures than graphs, generalizing results from graphs to hypergraphs is usually far from straightforward and frequently gives rise to new phenomena. For example, there are multiple ways (depending on how to define degrees and cycles in hypergraphs) to extend the classical result of Dirac on Hamilton cycles to hypergraphs -- none of them has an easy proof. The Dirac problems, and related matching and packing problems have received considerable attention lately. Modern tools, e.g., the absorbing method and the regularity method, have helped to generate new results, and yet many fundamental problems in the area remain unsolved. The PI plans to tackle many outstanding problems in the area, developing the extremal theory of hypergraphs.