Stephen Hawking has revealed from beyond the grave his final scientific theory - that the universe is a hologram.

The cosmologist, who died on March 14, has challenged previous theories of cosmic "inflation" and the "multiverse" in a new paper published in the Journal Of High Energy Physics.

Scientists generally believe that for a tiny fraction of a second after the Big Bang, the universe expanded incredibly rapidly before settling into its present state, filled with stars and galaxies - the inflation theory.

But some have proposed that, on a grander global scale, inflation goes on for ever, giving rise to a "multiverse" - a number of different universes with their own laws of physics.

Prof Hawking was always troubled by this idea, which at a fundamental level cannot be reconciled with Einstein's theory of General Relativity. In an interview last year he said: "I have never been a fan of the multiverse."