Inflation In Supergravity Research Articles

Reheating Temperature from D-Term Cosmological Inflation Braneworld

The D-term inflation in supergravity, in the braneworld Randall Sundrum II (RSII) context, has been proposed to solve some problems related to the four-dimensional inflation model. That scenario is based on a modification of the Friedmann equation by the addition of the fifth dimension, which corresponds to an energy, called brane tension λ. Therefore, we propose the investigation of the brane effect on the reheating epoch. In this context, we have analyzed the process of reheating and focused on the variation of the temperature value Tre. We found that it depends on all parameters, and the value found is in the range Tre ∼ (7.5 × 108−8 × 1010) GeV, which is consistent with the thermal leptogenesis (Tre ≥ 108 GeV).

Unified no-scale attractors

We have presented previously a general treatment of Starobinsky-like inflation in no-scale supergravity where the tensor-to-scalar ratio r = 3(1 − ns)2, and ns is the tilt of the scalar perturbations. In particular, we have shown how this scenario can be unified with modulus fixing, supersymmetry breaking and a small cosmological constant. In this paper we extend these constructions to inflationary models based on generalized no-scale structures. In particular, we consider alternative values of the curvature parameter, α < 1, as may occur if not all the complex Kähler moduli contribute to driving inflation, as well as α > 1, as may occur if complex structure moduli also contribute to driving inflation. In all cases, we combine these α-Starobinsky inflation models with supersymmetry breaking and a present-day cosmological constant, allowing for additional contributions to the vacuum energy from stages of gauge symmetry breaking.

Realising mutated hilltop inflation in supergravity

We present N=1 supergravity models of mutated hilltop inflation (MHI) for both large and small field sectors. Models with canonical kinetic terms are developed based on a shift symmetric Kähler potential in inflaton superfield, and with a superpotential linear in Goldstino superfield. We also construct models with non-canonical kinetic terms for MHI by generalising the shift symmetry. We found that a good fraction of the models can address the entire branch of MHI in a single framework.

A microscopic model for inflation from supersymmetry breaking

We have proposed recently a framework for inflation driven by supersymmetry breaking with the inflaton being a superpartner of the goldstino, that avoids the main problems of supergravity inflation, allowing for: naturally small slow-roll parameters, small field initial conditions, absence of a (pseudo)scalar companion of the inflaton, and a nearby minimum with tuneable cosmological constant. It contains a chiral multiplet charged under a gauged R-symmetry which is restored at the maximum of the scalar potential with a plateau where inflation takes place. The effective field theory relies on two phenomenological parameters corresponding to corrections to the Kähler potential up to second order around the origin. The first guarantees the maximum at the origin and the second allows the tuning of the vacuum energy between the F- and D-term contributions. Here, we provide a microscopic model leading to the required effective theory. It is a Fayet–Iliopoulos model with two charged chiral multiplets under a second mathrm{U}(1) R-symmetry coupled to supergravity. In the Brout–Englert–Higgs phase of this mathrm{U}(1), the gauge field becomes massive and can be integrated out in the limit of small supersymmetry breaking scale. In this work, we perform this integration and we show that there is a region of parameter space where the effective supergravity realises our proposal of small field inflation from supersymmetry breaking consistently with observations and with a minimum of tuneable energy that can describe the present phase of our Universe.

Starobinsky-like inflation and soft-SUSY breaking

We study a version of Starobinsky-like inflation in no-scale supergravity (SUGRA) where a Polonyi term in the hidden sector breaks supersymmetry (SUSY) after inflation, providing a link between the gravitino mass and inflation. We extend the theory to the visible sector and calculate the soft-SUSY breaking parameters depending on the modular weights in the superpotential and choice of Kähler potential. We are led to either no-scale SUGRA or pure gravity mediated SUSY breaking patterns, but with inflationary constraints on the Polonyi term setting a strict upper bound on the gravitino mass m3/2< 103 TeV. Since gaugino masses are significantly lighter than m3/2, this suggests that SUSY may be discovered at the LHC or FCC.

Inflation, dark energy, and dark matter in supergravity

We discuss the physical applications of supergravity to the dark side of our universe, comprising cosmological inflation, dark energy, and dark matter (DM). Supergravity is the meeting point of cosmology, gravity, and high‐energy physics of elementary particles, which makes it the natural framework to unify fundamental interactions and fundamental scales under Planck scale. In order to make our presentation accessible to a larger audience, we skip all technical details about supergravity theory and concentrate on the conceptual issues of supergravity applications to cosmology. We conjecture the gravitational origin of the cosmological inflation (in the modified gravity), the dark energy (as the positive cosmological constant), and the DM (made of gravitino particles) in supergravity.

Unitarity-safe models of non-minimal inflation in supergravity

We show that models of chaotic inflation based on the phi ^p potential and a linear non-minimal coupling to gravity, f_{{mathcal {R}}}=1+c_{{mathcal {R}}}phi , can be done consistent with data in the context of Supergravity, retaining the perturbative unitarity up to the Planck scale, if we employ logarithmic Kähler potentials with prefactors -p(1+n) or -p(n+1)-1, where -0.035lesssim nlesssim 0.007 for p=2 or -0.0145lesssim nlesssim 0.006 for p=4. Focusing, moreover, on a model employing a gauge non-singlet inflaton, we show that a solution to the mu problem of MSSM and baryogenesis via non-thermal leptogenesis can be also accommodated.

Axion isocurvature perturbations in low-scale models of hybrid inflation

The quantum chromodynamics (QCD) axion solves the strong $CP$ problem and represents an attractive particle candidate for cold dark matter (CDM). However, quantum fluctuations of the axion field during inflation easily result in large CDM isocurvature perturbations that are in conflict with observations of the cosmic microwave background. In this paper, we demonstrate how this problem can be solved in low-scale models of hybrid inflation that may emerge from supersymmetric grand unified theories. We consider both F-term hybrid inflation and D-term hybrid inflation in supergravity, explicitly taking into account the effect of hidden-sector supersymmetry breaking. We discuss the production of cosmic strings and show how the soft terms in the scalar potential readily allow us to achieve the correct scalar spectral index. In both cases, we are able to identify large regions in parameter space that are consistent with all constraints. In particular, we find that evading the CDM isocurvature constraint always requires a small Yukawa or gauge coupling of $\mathcal{O}({10}^{\ensuremath{-}3})$ or smaller. This translates into upper bounds on the gravitino mass of $\mathcal{O}({10}^{5})\text{ }\text{ }\mathrm{GeV}$ in F-term hybrid inflation and $\mathcal{O}({10}^{9})\text{ }\text{ }\mathrm{GeV}$ in D-term hybrid inflation. Our results point to interesting scenarios in well-motivated parameter regions that will be tested in future axion and cosmic microwave background experiments.

Induced-gravity GUT-scale Higgs inflation in supergravity

Models of induced-gravity inflation are formulated within Supergravity employing as inflaton the Higgs field which leads to a spontaneous breaking of a U(1)_{B-L} symmetry at M_mathrm{GUT}=2cdot 10^{16}~{mathrm{GeV}}. We use a renormalizable superpotential, fixed by a U(1) R symmetry, and Kähler potentials which exhibit a quadratic non-minimal coupling to gravity with or without an independent kinetic mixing in the inflaton sector. In both cases we find inflationary solutions of Starobinsky type whereas in the latter case, others (more marginal) which resemble those of linear inflation arise too. In all cases the inflaton mass is predicted to be of the order of 10^{13}~{mathrm{GeV}}. Extending the superpotential of the model with suitable terms, we show how the MSSM mu parameter can be generated. Also, non-thermal leptogenesis can be successfully realized, provided that the gravitino is heavier than about 10~{mathrm{TeV}}.

Chromo-natural inflation in Supergravity

We present supergravity realizations of chromo-natural inflationary models. We show that by using superpotentials with “imaginary” holomorphic functions of the inflaton one can obtain effective theories of inflation that are also consistent truncations of the original supergravity models.

Modulus D-term inflation

We propose a new model of single-field D-term inflation in supergravity, where the inflation is driven by a single modulus field which transforms non-linearly under the U(1) gauge symmetry. One of the notable features of our modulus D-term inflation scenario is that the global U(1) remains unbroken in the vacuum and hence our model is not plagued by the cosmic string problem which can exclude most of the conventional D-term inflation models proposed so far due to the CMB observations.

Hybrid inflation in quasiminimal supergravity with monotonic inflationary potential

We show how supersymmetric hybrid inflation with scalar spectral index $n_{\rm s}\simeq 0.96 - 0.97$ is realized in the context of quasi-minimal supergravity if we insist that the inflationary potential not exhibit any local minima. We also address the problem of the initial conditions for both monotonic and non-monotonic inflationary potentials.

Gravitational Waves, μ Term and Leptogenesis from B − L Higgs Inflation in Supergravity

We consider a renormalizable extension of the minimal supersymmetric standard model endowed by an R and a gauged B − L symmetry. The model incorporates chaotic inflation driven by a quartic potential, associated with the Higgs field which leads to a spontaneous breaking of U(1) B − L , and yields possibly detectable gravitational waves. We employ quadratic Kähler potential with a prominent shift-symmetric part proportional to c − and a tiny violation, proportional to c + , included in a logarithm with prefactor − N &lt; 0 . An explanation of the μ term of the MSSM is also provided, consistently with the low energy phenomenology, under the condition that one related parameter in the superpotential is somewhat small. Baryogenesis occurs via non-thermal leptogenesis which is realized by the inflaton’s decay to the lightest or next-to-lightest right-handed neutrino with masses lower than 1.8 × 10 13 GeV. Our scenario can be confronted with the current data on the inflationary observables, the baryon asymmetry of the universe, the gravitino limit on the reheating temperature and the data on the neutrino oscillation parameters, for 0.012 ≲ c + / c − ≲ 1/N and gravitino as light as 1 TeV.

Toward pole inflation and attractors in supergravity: Chiral matter field inflation

In string-inspired supergravity theory, K\"{a}hler metric of chiral matter fields often has a pole. Such K\"{a}hler metric is interesting from the viewpoint of the framework of the pole inflation, where the scalar potential can be stretched out to be flat around the pole for a canonically normalized field and inflation can be realized. However, when K\"{a}hler metric has a pole, the scalar potential can also have a pole at the same point in supergravity theory. We study such supergravity models with the pole, and provide numerical analysis of inflationary dynamics and resultant density perturbation. In contrast with usual pole inflation models, inflation in this supergravity based model occurs not on the pole but region apart from the pole. We show that the existence of the pole in the scalar potential is crucial nevertheless. We also examine attractor behavior of our model.

Sneutrino driven GUT inflation in supergravity

In this paper, we embed the model of flipped GUT sneutrino inflation — in a flipped SU(5) or SO(10) set up — developed by Ellis et al. in a supergravity framework. The GUT symmetry is broken by a waterfall which could happen at early or late stage of the inflationary period. The full field dynamics is thus studied in detail and these two main inflationary configurations are exposed, whose cosmological predictions are both in agreement with recent astrophysical measurements. The model has an interesting feature where the inflaton has natural decay channels to the MSSM particles allowed by the GUT gauge symmetry. Hence it can account for the reheating after the inflationary epoch.

O' R inflation in F-term supergravity

The supersymmetric realization of inflation in F-term supergravity is usually plagued by the well known “η” problem. In this paper, a broad class of small-field examples is realized by employing general O' Raifeartaigh superpotentials, where the moduli is identified as the massless inflaton. For illustration we present the simplest example in detail, which can be considered as a generalization of hybrid inflation.

No-scale mu -term hybrid inflation

To solve the fine-tuning problem in mu -term hybrid inflation, we will realize the supersymmetry scenario with the TeV-scale supersymmetric particles and intermediate-scale gravitino from anomaly mediation, which can be consistent with the WMAP and Planck experiments. Moreover, we for the first time propose the mu -term hybrid inflation in no-scale supergravity. With four scenarios for the SU(3)_Ctimes SU(2)_Ltimes SU(2)_Rtimes U(1)_{B-L} model, we show that the correct scalar spectral index n_s can be obtained, while the tensor-to-scalar ratio r is predicted to be tiny, about 10^{-10}–10^{-8}. Also, the SU(2)_Rtimes U(1)_{B-L} symmetry breaking scale is around 10^{14} GeV, and all the supersymmetric particles except gravitino are around the TeV scale, while the gravitino mass is around 10^{9}–10^{10} GeV. Considering the complete potential terms linear in S, we for the first time show that the tadpole term, which is the key for such kind of inflationary models to be consistent with the observed scalar spectral index, vanishes after inflation. Thus, to obtain the mu term, we need to generate the supersymmetry breaking soft term A^{S Phi Phi '}_{kappa } kappa S Phi Phi ' due to A^{S Phi Phi '}_{kappa }=0 in no-scale supergravity, where Phi and Phi ' are vector-like Higgs fields at high energy. We show that the proper A^{S Phi Phi '}_{kappa } kappa S Phi Phi ' term can be obtained in the M-theory inspired no-scale supergravity. We also point out that A^{S Phi Phi '}_{kappa } around 700 GeV can be generated via the renormalization group equation running from string scale. We briefly comment on the supersymmetry phenomenological consequences as well.

Gravitino problem in minimal supergravity inflation

We study non-thermal gravitino production in the minimal supergravity inflation. In this minimal model utilizing orthogonal nilpotent superfields, the particle spectrum includes only graviton, gravitino, inflaton, and goldstino. We find that a substantial fraction of the cosmic energy density can be transferred to the longitudinal gravitino due to non-trivial change of its sound speed. This implies either a breakdown of the effective theory after inflation or a serious gravitino problem.

No-scale supergravity inflation: A bridge between string theory and particle physics?

The plethora of recent and forthcoming data on the cosmic microwave background (CMB) data are stimulating a new wave of inflationary model-building. Naturalness suggests that the appropriate framework for models of inflation is supersymmetry. This should be combined with gravity in a supergravity theory, whose specific no-scale version has much to commend it, e.g. its derivation from string theory and the flat directions in its effective potential. Simple no-scale supergravity models yield predictions similar to those of the Starobinsky [Formula: see text] model, though some string-motivated versions make alternative predictions. Data are beginning to provide interesting constraints on the rate of inflaton decay into Standard Model particles. In parallel, LHC and other data provide significant constraints on no-scale supergravity models, which suggest that some sparticles might have masses close to present experimental limits.

Primordial black holes as dark matter in supergravity inflation models

We propose a novel scenario to produce abundant primordial black holes (PBHs) in new inflation which is a second phase of a double inflation in the supergravity frame work. In our model, some preinflation phase before the new inflation is assumed and it would be responsible for the primordial curvature perturbations on the cosmic microwave background scale, while the new inflation produces only the small scale perturbations. Our new inflation model has linear, quadratic, and cubic terms in its potential and PBH production corresponds with its flat inflection point. The linear term can be interpreted to come from a supersymmetry-breaking sector, and with this assumption, the vanishing cosmological constant condition after inflation and the flatness condition for the inflection point can be consistently satisfied.