TY - JOUR

T1 - Cosmological moduli problem, supersymmetry breaking, and stability in postinflationary cosmology

AU - Banks, T.

AU - Berkooz, M.

AU - Steinhardt, P. J.

PY - 1995

Y1 - 1995

N2 - We review scenarios that have been proposed to solve the cosmological problem caused by moduli in string theory, the postmodern Polonyi problem (PPP). In particular, we discuss the difficulties encountered by the apparently "trivial" solution of this problem, in which moduli masses are assumed to arise from nonperturbative, SUSY-preserving, dynamics at a scale higher than that of SUSY breaking. This suggests a powerful cosmological vacuum selection principle in superstring theory. However, we argue that if one eschews the possibility of cancellations between different exponentials of the inverse string coupling, the mechanism described above cannot stabilize the dilaton. Thus, even if supersymmetric dynamics gives mass to the other moduli in string theory, the dilaton mass must be generated by SUSY breaking, and dilaton domination of the energy density of the Universe cannot be avoided. We conclude that the only proposal for solving the PPP that works is the intermediate scale inflation scenario of Randall and Thomas. However, we point out that all extant models have ignored unavoidably large inhomogeneities in the cosmological moduli density at very early times, and speculate that the effects associated with nonlinear gravitational collapse of these inhomogeneities may serve as an efficient mechanism for converting moduli into ordinary matter. As an important by-product of this investigation we show that in a postinflationary universe minima of the effective potential with a negative cosmological constant are not stationary points of the classical equations of scalar field cosmology. Instead, such points lead to catastrophic gravitational collapse of that part of the Universe which is attracted to them. Thus postinflationary cosmology dynamically chooses non-negative values of the cosmological constant. This implies that supersymmetry must be broken in any sensible inflationary cosmology. We suggest that further study of the cosmology of moduli will lead to additional important insight about cosmology, SUSY breaking, and the choice of the vacuum in superstring theory.

AB - We review scenarios that have been proposed to solve the cosmological problem caused by moduli in string theory, the postmodern Polonyi problem (PPP). In particular, we discuss the difficulties encountered by the apparently "trivial" solution of this problem, in which moduli masses are assumed to arise from nonperturbative, SUSY-preserving, dynamics at a scale higher than that of SUSY breaking. This suggests a powerful cosmological vacuum selection principle in superstring theory. However, we argue that if one eschews the possibility of cancellations between different exponentials of the inverse string coupling, the mechanism described above cannot stabilize the dilaton. Thus, even if supersymmetric dynamics gives mass to the other moduli in string theory, the dilaton mass must be generated by SUSY breaking, and dilaton domination of the energy density of the Universe cannot be avoided. We conclude that the only proposal for solving the PPP that works is the intermediate scale inflation scenario of Randall and Thomas. However, we point out that all extant models have ignored unavoidably large inhomogeneities in the cosmological moduli density at very early times, and speculate that the effects associated with nonlinear gravitational collapse of these inhomogeneities may serve as an efficient mechanism for converting moduli into ordinary matter. As an important by-product of this investigation we show that in a postinflationary universe minima of the effective potential with a negative cosmological constant are not stationary points of the classical equations of scalar field cosmology. Instead, such points lead to catastrophic gravitational collapse of that part of the Universe which is attracted to them. Thus postinflationary cosmology dynamically chooses non-negative values of the cosmological constant. This implies that supersymmetry must be broken in any sensible inflationary cosmology. We suggest that further study of the cosmology of moduli will lead to additional important insight about cosmology, SUSY breaking, and the choice of the vacuum in superstring theory.

UR - http://www.scopus.com/inward/record.url?scp=0000734033&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000734033&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.52.705

DO - 10.1103/PhysRevD.52.705

M3 - Article

AN - SCOPUS:0000734033

SN - 1550-7998

VL - 52

SP - 705

EP - 716

JO - Physical review D: Particles and fields

JF - Physical review D: Particles and fields

IS - 2

ER -