Gravitational Instability of the Vacuum and the Cosmological Constant Problem

Abstract

A mechanism for suppressing the cosmological constant is described, using a superconducting analogy in which fermions coupled to gravitons are in an unstable false vauum. The coupling of the fermions to gravitons and a screened attractive interaction among pairs of fermions generates fermion condensates with zero momentum and a phase transition induces a non-perturbative transition to a true vacuum state. This produces a positive energy gap $\Delta$ in the vacuum energy identified with $\sqrt{\Lambda }$, where $\Lambda$ is the cosmological constant. In the strong coupling limit, a large cosmological constant induces a period of inflation in the early universe, followed by a weak coupling limit in which $\sqrt{\Lambda }$ vanishes exponentially fast as the universe expands due to the dependence of the energy gap on the Fermi surface fermions, predicting a small cosmological constant in the early universe.

7 pages, no figures, Latex2e file using ws-ijmpa.cls file. Invited talk given at the Brown University VIIIth Workshop on QCD, 7-11 June 2004, Paris, France. To be published in the proceedings in Int. J. Mod. Phys. A