Towards a naturally small cosmological constant from branes in 6D supergravity
Abstract
We investigate the possibility of selftuning of the effective 4D cosmological constant in 6D supergravity, to see whether it could naturally be of order 1/ r^{4} when compactified on two dimensions having KaluzaKlein masses of order 1/ r. In the models we examine supersymmetry is broken by the presence of nonsupersymmetric 3branes (on one of which we live). If r were submillimeter in size, such a cosmological constant could describe the recentlydiscovered dark energy. A successful selftuning mechanism would therefore predict a connection between the observed size of the cosmological constant, and potentially observable effects in submillimeter tests of gravity and at the Large Hadron Collider. We do find selftuning inasmuch as 3branes can quite generically remain classically flat regardless of the size of their tensions, due to an automatic cancellation with the curvature and dilaton of the transverse two dimensions. We argue that in some circumstances sixdimensional supersymmetry might help suppress quantum corrections to this cancellation down to the bulk supersymmetrybreaking scale, which is of order 1/ r. We finally examine an explicit realization of the mechanism, in which 3branes are inserted into an anomalyfree version of SalamSezgin gauged 6D supergravity compactified on a 2sphere with nonzero magnetic flux. This realization is only partially successful due to a topological constraint which relates bulk couplings to the brane tension, although we give arguments why these relations may be stable against quantum corrections.
 Publication:

Nuclear Physics B
 Pub Date:
 March 2004
 DOI:
 10.1016/j.nuclphysb.2003.12.015
 arXiv:
 arXiv:hepth/0304256
 Bibcode:
 2004NuPhB.680..389A
 Keywords:

 High Energy Physics  Theory
 EPrint:
 31 pages, 1 figure. Uses JHEP class. Expanded discussions in Introduction, Section 3.2 (Quantum Corrections) and Section 4.2 (Topological Constraint). Note added on subsequent related articles. Results unchanged