Successive Shortest Structures in Random Graphs

Lead Research Organisation: Royal Holloway University of London
Department Name: Mathematics

Abstract

We are surrounded by networks: Transport networks, social networks, infection networks, the internet, and electrical grids to name just a few. The natural way to model these kind of networks mathematically are graphs. Some networks, for example most transport networks, are rather static or develop slowly whereas many networks change fast and often in a manner that is hard to predict. To capture this unpredictable nature of networks one considers random graphs where each connection is chosen (independently) at random or, as in our project, one considers random weights on all possible connections. The research of random graphs does not only give us insights in real-world networks but also yields interesting and beautiful mathematics.
In this project we want to consider the effects of repeatedly removing structures from a complete graph with random edge weights. For example, we start with a network in which all connections are present and have a weight or length that is randomly distributed (independently from all the other weights). We have two special sites in our network and want to find the shortest path between them. With current methods that is easy to do as one can exploit the independence of the edges and can give a very precise prediction on the length of the path. When one removes this path and wants to find the next best path one cannot use the independence straight forwardly as one has already revealed most of the weights of the network when finding the first shortest path. In this project we investigate new approaches and methods to give very precise estimations on the length of the second shortest path, the third shortest path and so on. We also consider different structures to shortest paths to find common themes or differences.

Publications

10 25 50
 
Description We have been able to give very accurate predictions on the length of the kth shortest paths in complete graphs with random edge weights. Here the kth shortest path is the shortest path that is obtained after the edges of the first k-1 shortest paths have successively been deleted. We have also made first steps in comparing these results if one is interested in the cheapest structure containing k edge disjoint paths.
Exploitation Route Our findings open up interesting questions about other cheapest structures and also about other host graphs. We had interesting discussions about our results and future directions at conferences.
Sectors Digital/Communication/Information Technologies (including Software)

 
Description Exploring Maths 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Roughly 30 schools visited Royal Holloway University of London for a day of talks, workshops and a campus tour. There was also a session explicitely for teachers on the topic of "Transition from School to University". The purpose of these event was to show Year 12 students (and teachers) how varied and interesting studying mathematics is and to motivate them to consider to study mathematics (or a related subject).
Year(s) Of Engagement Activity 2022
URL https://exploringmaths.rhul.ac.uk/
 
Description School Visit (Eden School) 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact 60 pupils and 3 teachers attended for a school visit to the research organisation. We organised talks and a workshop during which there was time to interact with staff and students. A lot of interesting questions were asked and the school was very keen to repeat this day as this event sparked a real interest in the student to continue studying mathematics. This was a girl's school with a high proportion of students on free school meals.
Year(s) Of Engagement Activity 2022