Geometric deep learning

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Structures encountered in our everyday lives such as social networks, proteins and molecules, products sold online, and others are best interpreted as a graph due to the unique relationships between datapoints, such as the number of retweets between two users on Twitter or the type of bond between two atoms. As opposed to classical deep learning which was designed for Euclidean, more 'grid-like' geometry, graph machine learning (a subset of geometric deep learning) is a field of machine learning that takes advantage of additional non-Euclidean structure to improve models with applications in drug discovery, sociology and more.This project aims to enhance graph machine learning methods with ideas from differential geometry, the study of smooth shapes and manifolds. While early works in graph machine learning largely take inspiration from generalising existing deep learning models such as convolutional neural networks, differential geometry offers an orthogonal source of increasing sophistication due to its vast, and in this context largely unexplored, wealth of concepts and theoretical results established over many years. The first work in this project "Understanding over-squashing and bottlenecks on graph via curvature" uses new theoretical results on graphs based on Ricci curvature, a key concept from differential geometry, to design and evaluate a new pre-processing method on graphs that improved performance of existing graph neural networks on all datasets tested. Future works will include designing new model architectures using curvature to evolve how information travels across a graph alongside the model processes the features (a curvature-based neural network resembling a Beltrami flow), and extending existing differential equation-based graph models to use stochastic differential equations, allowing for the modelling of graph datasets that evolve randomly through time. All these directions of research are first-of-their-kind and form part of an exciting renaissance of using different geometries to expand the applications in which machine learning can be used.This project falls within the ESPRC Geometry and Topology research area under the Mathematical Sciences theme, as the novelty of the research has a solid footing in differential geometry and geometric deep learning. It also is likely to intersect with other themes, as we aim to directly apply powerful concepts from geometry to the world of machine learning to propose new, efficient methods and models in fields such as biology and sociology.