"Among the myriad other scientific investigations pursued by Hawking over the years are the study of quantum cosmology, cosmic inflation, helium production in anisotropic Big Bang universes, "large N" cosmology, the density matrix of the universe, the topology and structure of the universe, baby universes, Yang-Mills instantons and the S matrix, anti-de Sitter space, quantum entanglement and entropy, the nature of space and time and the arrow of time, spacetime foam, string theory, supergravity, Euclidean quantum gravity, the gravitational Hamiltonian, the Brans-Dicke and Hoyle-Narlikar theories of gravitation, gravitational radiation, holography, time symmetry and wormholes."