Range Of Gravitino Mass Research Articles

Trans-Planckian censorship and inflation in grand unified theories

The recently proposed trans-Planckian censorship conjecture (TCC) amounts to the claim that inflation models with an inflationary energy scale larger than Λinfmax∼109GeV belong to the swampland, i.e., cannot be embedded into a consistent theory of quantum gravity. In this paper, we point out that this constraint can be readily satisfied in D-term hybrid inflation (DHI), which is a well-motivated inflation scenario in the context of supersymmetric grand unification. In DHI, the amplitude of the primordial scalar power spectrum originates from a Fayet–Iliopoulos term of the order of the unification scale, ξ∼1016GeV. At the same time, the TCC results in an upper bound on the corresponding gauge coupling constant of gmax∼10−14. We are able to show that this constraint translates into an upper bound on the gravitino mass of m3/2max∼10MeV, which opens the possibility that dark matter is accounted for by thermally produced gravitinos, if the reheating temperature is close to Treh∼100TeV. Interestingly enough, a somewhat similar gravitino mass range has recently been derived in a model that aims at explaining dark energy in terms of axion quintessence and resolving the Hubble tension by means of decaying gravitino dark matter.

Reheating processes after Starobinsky inflation in old-minimal supergravity

We study reheating processes and its cosmological consequences in the Starobinsky model embedded in the old-minimal supergravity. First, we consider minimal coupling between the gravity and matter sectors in the higher curvature theory, and transform it to the equivalent standard supergravity coupled to additional matter superfields. We then discuss characteristic decay modes of the inflaton and the reheating temperature $T_{\rm R}$. Considering a simple model of supersymmetry breaking sector, we estimate gravitino abundance from inflaton decay, and obtain limits on the masses of gravitino and supersymmetry breaking field. We find $T_{\rm R}\simeq 1.0\times10^9$ GeV and the allowed range of gravitino mass as $10^4$ GeV $\lesssim m_{3/2} \lesssim 10^5$ GeV, assuming anomaly-induced decay into the gauge sector as the dominant decay channel.

Soft leptogenesis and gravitino dark matter in gauge mediation

We study soft leptogenesis in gauge mediated supersymmetry breaking models with an enhanced A-term for the right-handed neutrino. We find that this scenario can explain the baryon asymmetry of the present universe, consistently with the gravitino dark matter for a wide range of gravitino mass m3/2=O(MeV)–O(GeV). We also propose an explicit model which induces the necessary A-term for the right-handed neutrino.

Cosmology of F-theory GUTs

In this paper we study the interplay between the recently proposed F-theory GUTs and cosmology. Despite the fact that the parameter range for F-theory GUT models is very narrow, we find that F-theory GUTs beautifully satisfy most cosmological constraints without any further restrictions. The viability of the scenario hinges on the interplay between various components of the axion supermultiplet, which in F-theory GUTs is also responsible for breaking supersymmetry. In these models, the gravitino is the LSP and develops a mass by eating the axino mode. The radial component of the axion supermultiplet known as the saxion typically begins to oscillate in the early Universe, eventually coming to dominate the energy density. Its decay reheats the Universe to a temperature of ~ 1 GeV, igniting BBN and diluting all thermal relics such as the gravitino by a factor of ~ 10^(-4) - 10^(-5) such that gravitinos contribute a sizable component of the dark matter. In certain cases, non-thermally produced relics such as the axion, or gravitinos generated from the decay of the saxion can also contribute to the abundance of dark matter. Remarkably enough, this cosmological scenario turns out to be independent of the initial reheating temperature of the Universe. This is due to the fact that the initial oscillation temperature of the saxion coincides with the freeze out temperature for gravitinos in F-theory GUTs. We also find that saxion dilution is compatible with generating the desired baryon asymmetry from standard leptogenesis. Finally, the gravitino mass range in F-theory GUTs is 10-100 MeV, which interestingly coincides with the window of values required for the decay of the NLSP to solve the problem of Li(7) over-production.

Gauge mediation with D-term SUSY breaking

We construct a gauge-mediation model with a D-term supersymmetry (SUSY) breaking. R-symmetry breaking necessary for generating the SUSY Standard Model gaugino masses is given by gaugino condensation of a strongly coupled gauge theory in the hidden sector. The energy scale of the strong dynamics of the hidden sector gauge theory should be around the messenger mass scale M, or otherwise perturbative calculations would be reliable and would lead to negative soft mass squared for squarks and sleptons. Thus, all the mass scales are controlled by a virtually single parameter, D/M. This model covers a very wide range of gravitino mass, m3/2≃1eV–100TeV. Possible embeddings of the model in string theory are also discussed.

Hadronic axion model in gauge-mediated supersymmetry breaking

A simple hadronic axion model is proposed in the framework of gauge-mediated supersymmetry breaking. Dynamics of Peccei-Quinn symmetry breaking is governed by supersymmetry breaking effects and the Peccei-Quinn breaking scale f PQ is inversely proportional to the gravitino mass. The gravitino mass range which corresponds to the axion window f PQ≃10 9 GeV – 10 13 GeV lies in the region predicted by gauge-mediated supersymmetry breaking models. The model is also shown to be cosmologically viable.

Cosmological constraints on the light stable gravitino

Cosmological constraints when the gravitino is the lightest superparticle are studied. From the condition that the relic gravitinos should not overclose the universe, the upper bound on the reheating temperature of the universe is found to be 10 2–10 10 GeV in a range of gravitino mass 10 −5–10 GeV. Furthermore, if the decay of the next-to-the-lightest superparticle produces sizable high energy photons, constraints from the light element (D, 3He, 4He) photodestruction exclude a range of the gravitino mass.

Hadronic decays of cosmological gravitinos

We discuss a variety of effects due to the thermalisation and possible annihilation of relativistic protons and antiprotons from the decay of cosmological gravitinos. For a rather narrow range of gravitino mass around 250 GeV, the photons produced by inverse “Compton” scattering of nucleons off the thermal radiation are of the right energy to photodissociate helium 4, creating deuterium and helium 3. In a supersymmetric inflationary universe, this leads to a maximum reheating temperature of about 1.2 × 10 7 GeV for this particular gravitino mass.