This volume contains nine survey articles based on plenary lectures given at the 28th British Combinatorial Conference, hosted online by Durham University in July 2021. This biennial conference is a well-established international event, attracting speakers from around the world. Written by some of the foremost researchers in the field, these surveys provide up-to-date overviews of several areas of contemporary interest in combinatorics. Topics discussed include maximal subgroups of finite simple groups, Hasse-Weil type theorems and relevant classes of polynomial functions, the partition complex, the graph isomorphism problem, and Borel combinatorics. Representing a snapshot of current developments in combinatorics, this book will be of interest to researchers and graduate students in mathematics and theoretical computer science.

Interval structures arise naturally in many applications, as in genetics, molecular biology, resource allocation, and scheduling, among others. Such structures are often modeled with graphs, such as interval and tolerance graphs, which have been widely studied. In this book we mainly investigate these classes of graphs, as well as a scheduling problem. We present solutions to some open problems, along with some new representation models that enable the design of new efficient algorithms. In the context of interval graphs, we present the first polynomial algorithm for the longest path problem, whose complexity status was an open question. Furthermore, we introduce two matrix representations for both interval and proper interval graphs, which can be used to derive efficient algorithms. In the context of tolerance graphs, we present the first non-trivial intersection model, given by three-dimensional parallelepipeds, which enables the design of efficient algorithms for some NP-hard optimization problems. Furthermore, we prove that both recognition problems for tolerance and bounded tolerance graphs are NP-complete, thereby settling a long standing open question since 1982.