Big extra dimensions make Lambda too small

Abstract

I argue that the true quantum gravity scale cannot be much larger than the Planck length, because if it were then the quantum gravity-induced fluctuations in $\text{Lam}$ would be insufficient to produce the observed cosmic ``dark energy''. If one accepts this argument, it rules out scenarios of the ``large extra dimensions'' type. I also point out that the relation between the lower and higher dimensional gravitational constants in a Kaluza-Klein theory is precisely what is needed in order that a black hole's entropy admit a consistent higher dimensional interpretation in terms of an underlying spatio-temporal discreteness.

Comments: plainTeX, 9 pages, no figures To appear in a special issue of the Brazilian Journal of Physics devoted to the Proceedings of the Second International Workshop ``DICE 2004'' held September, 2004, Piombino, Italy. MOST CURRENT VERSION available at http://www.physics.syr.edu/~sorkin/some.papers/ or wherever my home-page is