Thread: The Superstring "Landscape" View Single Post


Urs Schreiber wrote in message news:... > Yes, after posting that message I had this idea, too, that the autor is > probably thinking of the fact that the _Hamiltomnian constraint_ vanishes. > That's why he says "at least classically", being aware of the well > understood case of 1+1 dimensions where the Hamiltonian constraint (L0 + > $\bar L_0)$ is "" only up a quantum shift. > > But if that's what the author is thinking of in that paragraph it really > makes me feel uneasy, because, as you indicated > > 1) the fact that the Hamiltonian constraint vanishes says little about the > energy content of the universe (much like $(L_0-1)|\psi>=0$ alone tells me > nothing about the mass of a string state $\psi)$ > > 2) the statement does not have anything to do with the figure that > accompanies it and the conclusions drawn from it (please anyone correct > me if I am wrong about this!) > > > (matter) energy-momentum tensor, which is exactly the > > "non-vanishing energy content" you are talking about. It is the > > Hamiltonian, though, which is the relevant quantity for > > thermodynamical considerations. > > Yes, that's what I would think. And this Hamiltonian does not vanish. I tend to disagree with you. The only properly defined Hamiltonian here is the Hamiltonian constraint (since we are in bounded space) and $it _does_$ vanish. I.e., instead of the usual Gibbs ensemble $\exp(-\beta H) we$ get just the identity density matrix. Now, since entropy is monotonously decreasing with the cosmological constant (see equation 2.7 on page 7; note R is monotonously decreasing with the cosmological constant) fluctuations from the metastable vacuum $at \phi_0$ (see figure 1) will indeed be suppressed by pure entropy considerations. > It's > > Kachru & Kallosh & Linde & Trivedi: > de Sitter vacua in string theory > http://www.arxiv.org/abs/hep-th/0301240 > > which started most of the landscape discussion, as far as I am aware. For > a nice summary of some of the effects discussed in there see J. Distler's > > "Digging up the landscape" > http://golem.ph.utexas.edu/~distler/...es/000359.html > > and > > "The discretium" > http://golem.ph.utexas.edu/~distler/...s/000348.html. > > Also see the sci.physics.strings archive for the thread > > "Conceptual question" > > where Shamit Kachru himself, together with J. Polchinski and W. Lerche, L. > Motl and A. Rajaraman discuss this issue. Thx! Best regards, Squark.