General considerations of the cosmological constant and the stabilization of moduli in the brane-world picture

We argue that the brane-world picture with matter-fields confined to 4-d do main walls and with gravitational interactions across the bulk disallows ad ding an arbitrary constant to the low-energy, 4-d effective theory - which finesses the usual cosmological constant problem. The analysis also points to difficulties in stabilizing moduli fields; as an alternative, we suggest scenarios in which the moduli motion is heavily damped by various cosmolog ical mechanisms and varying ultra-slowly with time. (C) 1999 Published by E lsevier Science B.V. All rights reserved.