Abstract
No-scale supergravity provides a successful framework for Starobinsky-like inflation models. Two classes of models can be distinguished depending on the identification of the inflaton with the volume modulus, $T$ (C-models), or a matter-like field, $\phi$ (WZ-models). When supersymmetry is broken, the inflationary potential may be perturbed, placing restrictions on the form and scale of the supersymmetry breaking sector. We consider both types of inflationary models in the context of high-scale supersymmetry. We further distinguish between models in which the gravitino mass is below and above the inflationary scale. We examine the mass spectra of the inflationary sector. We also consider in detail mechanisms for leptogenesis for each model when a right-handed neutrino sector, used in the seesaw mechanism to generate neutrino masses, is employed. In the case of C-models, reheating occurs via inflaton decay to two Higgs bosons. However, there is a direct decay channel to the lightest right-handed neutrino which leads to non-thermal leptogenesis. In the case of WZ-models, in order to achieve reheating, we associate the matter-like inflaton with one of the right-handed sneutrinos whose decay to the lightest right handed neutrino simultaneously reheats the Universe and generates the baryon asymmetry through leptogenesis.
Highlights
There are many motivations for supersymmetry including the solution to the hierarchy problem [1], gauge coupling unification [2], the stability of the Higgs vacuum [3], radiative electroweak symmetry breaking [4], and viable dark matter candidates [5]
Generic supergravity models often induce what is known as the η problem [8], which is addressed in a no-scale supergravity framework [9,10]
Before we discuss leptogenesis in the context of the two inflationary paradigms, we first review some of the general formalism for generating a baryon asymmetry from a lepton asymmetry induced by the out-of-equilibrium decay of a heavy right-handed neutrino
Summary
There are many motivations for supersymmetry including the solution to the hierarchy problem [1], gauge coupling unification [2], the stability of the Higgs vacuum [3], radiative electroweak symmetry breaking [4], and viable dark matter candidates [5]. The stability of the Higgs vacuum can be maintained in both high-scale supersymmetry [31] and nonsupersymmetric models [36], when an additional scalar field below 1010 GeV is present (which can drive radiative electroweak symmetry breaking). It is possible to construct viable models with a significantly higher supersymmetry breaking scale so that all the superpartners, except for the gravitino, lie above the inflationary scale [27,54,55,56] In this case, the gravitino with a mass of order m3=2 ≳ 0.1 EeV may play the role of dark matter. We focus on models of nonthermal leptogenesis [67] In this case, the inflaton decays directly to a right-handed neutrino which is out-of-equilibrium if its mass is larger than the reheating temperature TRH.
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