A Next-to-Minimal Supersymmetric Model of Hybrid Inflation

We propose a model of inflation based on a simple variant of the NMSSM, called $\phi$NMSSM, where the additional singlet $\phi$ plays the role of the inflaton in hybrid (or inverted hybrid) type models. As in the original NMSSM, the $\phi$NMSSM solves the $\mu$ problem of the MSSM via the VEV of a gauge singlet $N$, but unlike the NMSSM does not suffer from domain wall problems since the offending $Z_3$ symmetry is replaced by an approximate Peccei-Quinn symmetry which also solves the strong CP problem, and leads to an invisible axion with interesting cosmological consequences. The PQ symmetry may arise from a superstring model with an exact discrete $Z_3 \times Z_5$ symmetry after compactification. The model predicts a spectral index $n=1$ to one part in $10^{12}$.Comment: 17 pages, Latex; note added, accepted for Phys. Lett.

Threshold Effects And Perturbative Unification

We discuss the effect of the renormalization procedure in the computation of the unification point for running coupling constants. We explore the effects of threshold--crossing on the $\beta$--functions. We compute the running of the coupling constants of the Standard Model, between $m_Z$ and $M_P$, using a mass dependent subtraction procedure, and then compare the results with $\bar{MS}$, and with the $\theta$-- function approximation. We also do this for the Minimal Supersymmetric extension of the Standard Model. In the latter, the bounds on susy masses that one obtains by requiring perturbative unification are dependent, to some extent, on the procedure.Comment: 22 pages, REVTEX-2.1, 6 Post-Script figures are include

A Next-to-Minimal model of Hybrid Inflation in Effective Supergravity Theories

We propose a model of inflation based on a simple variant of the NMSSM, called $\phi$NMSSM where the additional singlet $\phi$ plays the role of the inflaton in hybrid (or inverted hybrid) type models. The $\phi$NMSSM solves the $\mu$ problem of the MSSM via the vacuum expectation value of the gauge singlet N, but also solves the strong CP problem through an approximate Peccei-Quinn symmetry. The potential energy which drives inflation originates from the F-term of the effective supergravity theory which result from a generic string theory. In the class of models considered the inflaton is protected from receiving mass during inflation by a Heisenberg symmetry, avoiding the $\eta$ problem.Comment: 4 pages, Latex, Talk given at Cosmo-98, Nov 199

F-term Hybrid Inflation in Effective Supergravity Theories

We show that the effective low energy supergravity theories which result from a generic string theory can provide a promising framework for models of hybrid inflation in which the potential energy which drives inflation originates from the F-term of the effective supergravity theory. In the class of models considered the inflaton is protected from receiving mass during inflation by a Heisenberg symmetry and the potential during inflation takes the positive definite form $V \sim |F|^2$, which allows the possibility that $V\ll m_{3/2}^2 M_P^2$. We discuss a toy example where this is realised, then describe the application of this result to realistic models focusing on a particular example in which the $\mu$ problem and the strong CP-problem are addressed

Non-linear metric perturbation enhancement of primordial gravitational waves

We present the evolution of the full set of Einstein equations during preheating after inflation. We study a generic supersymmetric model of hybrid inflation, integrating fields and metric fluctuations in a 3-dimensional lattice. We take initial conditions consistent with Eintein's constraint equations. The induced preheating of the metric fluctuations is not large enough to backreact onto the fields, but preheating of the scalar modes does affect the evolution of vector and tensor modes. In particular, they do enhance the induced stochastic background of gravitational waves during preheating, giving an energy density in general an order of magnitude larger than that obtained by evolving the tensors fluctuations in an homogeneous background metric. This enhancement can improve the expectations for detection by planned gravitational waves observatories.Comment: 5 pages, 4 eps figures, matches Phys. Rev. Lett. versio

Power suppression from disparate mass scales in effective scalar field theories of inflation and quintessence

A scalar potential coupled to other fields of large disparate masses will exhibit power suppression of the quantum loop corrections from these massive fields. Quintessence fields in the dark energy regime and inflaton fields during inflation often have a very large background field value. Thus any other field with its mass dependent on the quintessence/inflaton background field value through a moderate coupling will become very massive during the dark energy/inflation phase and its quantum corrections to the scalar effective potential will be suppressed. This concept is developed in this paper using the decoupling theorem. The problem then reduces to a quantitative question of the size of suppression effects within the parameter space of coupling constants, scalar field background value and renormalization scale. Some numerical examples are presented both for inflation and quintessence, but the approach is general and can be applied to any scalar field effective potential. The consequences to dark energy of the decoupling effect developed here is that the quintessence field need not just be an incredibly weakly interacting field, often added as simply an add-on to generate dark energy and have no other purpose. Instead, this quintessence field could play a central role in the particle physics dynamics at early times and then simply decouple at late times before the onset of the dark energy phase. For inflation a consequence is coupling of the inflaton to other fields can be much larger in certain models, without needing supersymmetry to control quantum corrections.Comment: 25 pages, 10 figure