Presentation on theme: "How to amaze your friends the link between mazes, murder and organised crime Chris Budd Chris Budd."— Presentation transcript:
How to amaze your friends the link between mazes, murder and organised crime Chris Budd Chris Budd
Most maths is taught as a subject which is Precise Careful Safe Logical Today we will look at combining maths and Murder Suicide Love Conquest Crime How an ancient idea has 21st Century applications!
Euler Circuit Can we find a route through the network which passes through each edge once and only once? Theorem: 1.Always if the network only has even nodes 2. Yes, if the network has two odd nodes, starting and finishing at an odd node 3. Otherwise never Proof: Tricky, but leads to a way to crack a maze
A B C A B C D D E E F F G G H I H I J J K K L L M M N N Centre Maze Network
A B C D E F G H I J K L M N Centre More generally.. Double up each of the paths Apply the Euler circuit theory
Using a network and some peanuts you can solve any maze Start at the entrance and take any path If you come to a new node then leave a peanut and take any new path If you come to an old node (or the end of a blind alley) and you are on a new path then turn back along this path If you come to an old node and you are on an old path then take a new path (or another old path if no new path exists) Never go down a path more than twice Alumni Challenge 2: Try this and Good Luck!
Networks have many other applications Social: Friendship, Sexual partners, FACEBOOK Organisational: Management, crime Technological: World-wide-web, Internet, power grid Information: DNA, Protein-Protein, Citations, word-of- mouth, gossip, retail Ecological: Food chains, disease & infection Moreno 1934 Systematic study of networks is a key application of maths to the 21st Century!!!
Friends (social network) Bob MaryDave Alice Richard Basil Chloe Six degrees of separation??
The Internet/world-wide-web Google exploits features of this to work, especially using the page-rank algorithm and eigenvalues of the adjacency matrices
Food web Scientific collaborations Sexual contacts
Different types of network developed to model various situations : this is what mathematicians do with their time …. Random: Erdos- Renyi Small-world: Watts-Strogatz (social) Barabasi-Albert: Internet, World-wide-web, Facebook
Mathematical features of a network : Nodal degree: Number of edges k attached to a node Proportion: P(k) probability a node has degree k Scaling laws and scale free networks: Random network but more often see Network resilience: How does the network connectivity eg. The average path length/node degree change as nodes/edges are removed? Understanding this is vital to the study of disease, power generation and to ….
Organised crime! How can we break up a crime network?
Method 1: Delete members at random at each time step
Method 2. Attack the member towards whom the previous victim had the highest degree of attachment. Assume that all victims are arrested, not murdered, and they inform the police of the person they most respect/trust/know.
Conclusions: Networks are a fascinating area of maths With a rich history which we can explore And great relevance to many aspects of the modern world including crime Which have the potential for almost limitless investigations, field trips and construction projects Truly they are a way to amaze your friends!
Networks lead naturally to interesting mathematical investigations of great practical relevance 1.Shortest distance l between two nodes: lowest number of nodes between them 6 degrees max of separation is claimed ?? Is this really true ?? 2.Degree of a node = number of edges that meet the node ?? What proportion p of nodes have degree k ??