What is the name of the theory proposed by Hawking and James Hartle?

The theory proposed by Stephen Hawking and James Hartle is the no-boundary proposal. It is also known as the Hartle–Hawking state or the no-boundary wave function.

Published in 1983, the proposal addresses the initial condition of the universe. Instead of assuming a sharp beginning with a conventional boundary, it treats the early universe using quantum cosmology and a geometry that is finite yet has no boundary—an idea often compared with the surface of a sphere, which has a limited area but no edge.

The proposal uses a path-integral approach in which possible histories of the universe contribute to its quantum state. It is not the same as the multiverse, cyclic-universe, or inflationary-universe models listed as alternatives. The no-boundary proposal can be used alongside inflationary ideas, but it concerns the universe’s quantum origin rather than being simply another name for inflation.