Thursday, February 9, 2006

Hartle-Hawking-Susskind unification

Interesting authors always attract an increased amount of attention. Stephen Hawking and Thomas Hertog have submitted a new paper

that proposes a certain unification of the Hartle-Hawking ideas about the wavefunction of the Universe with the concepts of the landscape. I have not yet analyzed the paper sufficiently deeply to describe it here but some readers may be ahead of me. So far I struggle with statements like "the histories of the Universe depend on the question we ask" and "the observations are determined by final boundary conditions".

The first statement violates my assumption that all current observations should be describable and explainable by the same set of "consistent histories", if you allow me to use the Gell-Mann-Hartle et al. interpretation of quantum mechanics. The second statement disagrees with my basic assumptions about causality.

I have almost forgotten what was Hawking's attitude to the anthropic principle. Then I realized that Hawking has said something wise about it that was meant to sound neutral - but that was eventually identified by David Gross as the "extreme anthropic principle": "All parameters of the visible Universe are assumptions - and we should only consider the conditional probabilities assuming that the parameters such as the particle masses are what they apparently are."

(Conditional probabilities play an important role in the new paper, too, and the ideas could actually be closely related.)

"Consequently, the message for the experimentalists is: Please don't measure anything else. Every new number you measure will have to be added to our awkward anthropic list of assumptions," David Gross interpreted Hawking's approach to the vacuum selection issues. ;-)