Tonight, Michael McGuigan has made a new step in his attempt to make the seesaw mechanism for the cosmological constant realistic:

Recall that Tom has proposed to interpret the cosmological constant - the curvature of empty space - as the primary effect and the supersymmetry breaking in particle physics as its consequence. This changes the question from "why is the cosmological constant so small" to the question "why is the supersymmetry breaking in particle physics so strong".

The supersymmetry breaking induced by the tiny curvature of our Universe would normally be negligible, and Tom circumvents this problem by suggesting that an important exponent in his power law is corrected from a classical value of 1/4 to the value of 1/8 by huge effects of virtual black holes whose loops are localized near the de Sitter horizon. The relation with the seesaw mechanism is not quite clear to me - although both methods of course try to obtain the same kind of result for the vacuum energy (but via different effects, I think).

Right now I don't have enough time to tell you exactly what I think about the proposal but the paper is rather concrete and tries to apply the Wheeler-DeWitt equation on various string-theoretical backgrounds. He seems to show that the off-diagonal elements of the vacuum energy (transitions) exist in three spacetime dimensions or less. Can you obtain these off-diagonal elements from Coleman-DeLuccia-like instantons? I believe that the proposal is interesting enough to be looked at.

Incidentally, Apple finally offers Mac users a decent operating system. It is called Windows XP.

## snail feedback (1) :

The attractiveness of gravitational seesaw is that it stresses the coincidence of three pairs of scales:

- The neutrino scale is near the cosmological constant.

- The electroweak scale is near the WIMP.

- The GUT scale is near the Planck scale

A problem is that it is near of being overdetermined: the difference between the electroweak scale and GUT is already "explained" from the running of the higgs mass term, and SeeSaw does the rest to fix all these three scales in particle physics.

On the other hand, I find interesting to note that the QFT limit of quantum gravity is to take Planck scale to infinity (ie Newton constant to zero), and then the seesaw also puts to zero the cosmological term. (and to infinity the GUT and to zero the neutrinos, and then what about renormalization group running coupling constants?)

Lubous, cound you find in Haloscan that comment of Smolin in 2006, where he stressed the closeness of some cosmological scales (cosmological constant, Pionner effect?) and the neutrino scale?

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