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After reviewing the motivations for cosmological inflation formulated in the formalism of supersymmetry, we argue that the appropriate framework is that of no-scale supergravity. We then show how to construct within this framework inflationary models whose predictions for the tilt in the spectrum of scalar perturbations, n s , and the ratio, r , of tensor and scalar perturbations coincide with those of the R + R 2 model of inflation proposed by Starobinsky. A more detailed study of no-scale supergravity reveals a structure that is closely related to that of R 2 modifications of the minimal Einstein–Hilbert action for general relativity, opening avenues for constructing no-scale de Sitter and anti-de Sitter models by combining pairs of Minkowski models, as well as generalizations of the original no-scale Starobinsky models of inflation. We then discuss the phenomenology of no-scale models of inflation, including inflaton decay and reheating, and then the construction of explicit scenarios based on SU(5), SO(10) and string-motivated flipped SU(5)×U(1) GUT models. The latter provides a possible model of almost everything below the Planck scale, including neutrino masses and oscillations, the cosmological baryon asymmetry and cold dark matter, as well as n s and r. [ABSTRACT FROM AUTHOR]

We study a new mechanism for the production of dark matter in the Universe which does not rely on thermal equilibrium. Dark matter is populated from the thermal bath subsequent to inflationary reheating via a massive mediator whose mass is above the reheating scale TRH. To this end, we consider models with an extra U(1) gauge symmetry broken at some intermediate scale (Mint ≃ 1010-1012 GeV). We show that not only does the model allow for gauge coupling unification (at a higher scale associated with grand unification) but it can provide a dark matter candidate which is a standard model singlet but charged under the extra U(1). The intermediate scale gauge boson(s) which are predicted in several E6/SO(10) constructions can be a natural mediator between dark matter and the thermal bath. We show that the dark matter abundance, while never having achieved thermal equilibrium, is fixed shortly after the reheating epoch by the relation TRH³/Mint4. As a consequence, we show that the unification of gauge couplings which determines Mint also fixes the reheating temperature, which can be as high as TRH ≃ 1011 GeV. [ABSTRACT FROM AUTHOR]

We present a model for cosmological inflation based on a no-scale supergravity sector with an SU(2, l)/SU(2) X U(l) Kähler potential, a single modulus T, and an inflaton superfield 1 described by a Wess-Zumino model with superpotential parameters (μ., Λ. When T is fixed, this model yields a scalar spectral index ns and a tensor-to-scalar ratio r that are compatible with the Planck measurements for values of Λ ≃ μ/3Mp. For the specific choice Λ = μ/3Mp, the model is a no-scale supergravity realization of the R + R2 Starobinsky model. [ABSTRACT FROM AUTHOR]

We consider the possibility that supersymmetry is broken above the inflationary mass scale and that the only "low" energy remnant of supersymmetry is the gravitino with a mass of the order of the EeV scale. The gravitino in this class of models becomes a candidate for the dark matter of the Universe. To avoid the overproduction of gravitinos from the decays of the next-to-lightest supersymmetric particle we argue that the supersymmetric spectrum must lie above the inflationary mass scale (MSUSY>10-5MP∼1013 GeV). Since m3/2≃MSUSY²/MP, we expect m3/2≳0.2 EeV. Cosmological constraints then predict a relatively large reheating temperature between 1010 and 1012 GeV. [ABSTRACT FROM AUTHOR]

We propose a complete cosmological scenario based on a flipped SU (5) × U (1) GUT model that incorporates Starobinsky-like inflation, taking the subsequent cosmological evolution carefully into account. A single master coupling, λ 6 , connects the singlet, GUT Higgs and matter fields, controlling 1) inflaton decays and reheating, 2) the gravitino production rate and therefore the non-thermal abundance of the supersymmetric cold dark matter particle, 3) neutrino masses and 4) the baryon asymmetry of the Universe. [ABSTRACT FROM AUTHOR]