A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame. Because inflation deals with Planck scale physics, the dilaton can be a strong candidate for identification with the inflaton. The model we used, cleared the $η$-problem and negative energy problem of potential at stable point, and appeared to predict successfully the values of observations at the inflation era.
We proved that the model explains WMAP observations appropriately. Moreover, a mechanism of SSB and Gravitino production just after the end of inflation is investigated. We have obtained power spectrum of the density perturbation as $\mathcal{P_R}_* \sim 2.438 \times 10^{-9}$ and the scalar spectral index as $n_{s*}\sim 0.9746$ and its tilt as $α_{s*}\sim -4.3 \times 10^{-4}$. The ratio between scalar power spectrum and tensor is predicted as $r\sim 6.8 \times 10^{-2}$, a prediction which seems in the range possibly observed by the Planck satellite soon. The gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. The reheating temperature is estimated by the stability condition of Boltzmann equation by using the decay rate of the dilaton S into gauginos as $T_R({\rm gaugino}) = 3.88 \times 10^{7} \,\, {\rm GeV}$. Though only one example of parameter choices has been discussed here, the other seven candidates of parameter choices that are compatible with WMAP data have already been found by the authors. Some of the examples show that the gauginos can be observed by LHC experiments. The plausible supergravity model of inflation which here we described will open the hope to construct a realistic theory of particle theory and cosmology in this framework.
After a period of inflationary expansion, the Universe reheated and reached full thermal equilibrium at the reheating temperature. In this talk, based on the paper, arXiv:0710.3349, we point out that, in the context of effective low-energy supersymmetric models, LHC measurements may allow one to determine reheating temperature as a function of the mass of the dark matter particle assumed to be either an axino or a gravitino. An upper bound on their mass and on the reheating temperature may also be derived.
Supersymmetric theories with gravitino dark matter generally do not allow the high reheating temperature required by thermal leptogenesis without running afoul of relic abundance or big bang nucleosynthesis constraints. We report on a successful search for parameter space that does satisfy these requirements. The main implication is the near degeneracy of the gluino with the other neutralinos in the spectrum. The leading discovery channel at the LHC for this scenario is through monojet plus missing energy events.
The low reheat temperature at the end of inflation from the gravitino bound constrains the creation of heavy Majorana neutrinos associated with models of leptogenesis. However, a detailed view of the reheating of the Universe at the end of inflation implies that the maximum temperature during reheating, $\Tmax$, can be orders of magnitude higher than the final reheat temperature. This then allows for the production of the heavy Majorana neutrinos needed for leptogenesis. We carry out the complementary calculation of the gravitino production during reheating and its dependence on $\Tmax$. We fi…
Models of leptogenesis are constrained by the low reheat temperature at the end of reheating associated with the gravitino bound. However a detailed view of reheating, in which the maximum temperature during reheating, $\Tmax$, can be orders of magnitude higher than the reheat temperature, allows for the production of heavy Majorana neutrinos needed for leptogenesis. But then one must also consider the possibility of enhanced gravitino production in such scenarios. In this article we consider gravitino production during reheating, its dependence on $\Tmax$, and its relevance for leptogenesis. …
A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame, so that the model explains WMAP observations very well. Gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. Seven cases of parameter choices are discussed here, among which some examples show the possibility of observation of gauginos by LHC experiments, which will give some hints of identity of dark matters. The reheating temperature, which is estimated by the stability condition…
We study the effects of the unstable gravitino on the big-bang nucleosynthesis. If the gravitino mass is smaller than \sim 10 TeV, primordial gravitinos produced after the inflation are likely to decay after the big-bang nucleosynthesis starts, and the light element abundances may be significantly affected by the hadro- and photo-dissociation processes as well as by the p n conversion process. We calculate the light element abundances and derived upper bound on the reheating temperature after the inflation. In our analysis, we calculate the decay parameters of the gravitino (i.e., lifetime and…
The presence of high reheating temperatures in the thermal history of the universe challenges supersymmetric scenarios owing to the gravitino problem. We revise a general R-parity conserving gravitino dark matter scenario with a stau as the next-to-lightest superparticle being particularly constrained by searches for heavy stable charged particles at the LHC. Imposing a variety of experimental and theoretical constraints we show that points with T_R > 10^9 GeV survive only in a very particular corner of parameter space.
Gravitino production and decay in the inflationary universe are reexamined. Assuming that the gravitino mainly decays into a photon and a photino, we calculate the upperbound on the reheating temperature. Compared to previous works, we have essentially improved the following two points: (i) the helicity $\pm\frac{3}{2}$ gravitino production cross sections are calculated by using the full relevant terms in the supergravity lagrangian, and (ii) the high energy photon spectrum is obtained by solving the Boltzmann equations numerically. Photo-dissociation of the light elements (D, T, $^3$He, $^4$H…
After a period of inflationary expansion, the Universe reheated and reached full thermal equilibrium at the reheating temperature T_R. In this work we point out that, in the context of effective low-energy supersymmetric models, LHC measurements may allow one to determine T_R as a function of the mass of the dark matter particle assumed to be either an axino or a gravitino. An upper bound on their mass may also be derived.
We show that a mini-thermal inflation occurs naturally in a class of gauge mediation models of supersymmetry (SUSY) breaking, provided that the reheating temperature T_R of the primary inflation is much higher than the SUSY-breaking scale, say T_R > 10^{10} GeV. The reheating process of the thermal inflation produces an amount of entropy, which dilutes the number density of relic gravitinos. This dilution renders the gravitino to be the dark matter in the present universe. The abundance of the gravitinos is independent of the reheating temperature T_R, once the gravtinos are thermally produced…
We review the phenomenology of gravitino dark matter within supergravity framework. Gravitino can be dark matter if it is the lightest supersymmetric particle, which is stable if R-parity is conserved. There are several distinct scenarios depending on what the next to lightest supersymmetric particle (NLSP) is. We discuss the constraints and summarize the phenomenology of neutralino, stau, stop and sneutrino NLSPs.
Considering gravitino dark matter scenarios, we study constraints on the reheating temperature of inflation. We present the gauge-invariant result for the thermally produced gravitino yield to leading order in the Standard Model gauge couplings. Within the framework of the constrained minimal supersymmetric Standard Model (CMSSM), we find a maximum reheating temperature of about 10^7 GeV taking into account bound-state effects on the primordial $^6$Li abundance. We show that late-time entropy production can relax this constraint significantly. Only with a substantial entropy release after the …
We have recently shown that, if the inflaton has a nonzero vacuum expectation value, it generically couples to any matter fields that appear in the superpotential at the tree level, and to any gauge sectors through anomalies in the supergravity. Through these processes, the inflaton decays into the supersymmetry breaking sector, producing many gravitinos. The inflaton also directly decays into a pair of the gravitinos. Taking account of these processes, we derive constraints on both inflation models and supersymmetry breaking scenarios for avoiding overproduction of the gravitinos.
We consider the dynamics of the supersymmetry-breaking scalar field and the production of dark matter gravitinos via its decay in a gauge-mediated supersymmetry breaking model with metastable vacuum. We find that the scalar field amplitude and gravitino density are extremely sensitive to the parameters of the hidden sector. For the case of an O'Raifeartaigh sector, we show that the observed dark matter density can be explained by gravitinos even for low reheating temperatures T_{R} < 10 GeV. Such low reheating temperatures may be implied by detection of the NLSP at the LHC if its thermal freez…
We investigate the possibility of probing high reheating temperature scenarios at the LHC, in supersymmetric models where the gravitino is the lightest supersymmetric particle, and the stau is the next-to-lightest supersymmetric particle. In such scenarios, the big-bang nucleosynthesis and the gravitino abundance give a severe upper bound on the gluino mass. We find that, if the reheating temperature is \sim 10^8 GeV or higher, the scenarios can be tested at the LHC with an integrated luminosity of O(1 fb^{-1}) at \sqrt{s}=7 TeV in most of the parameter space.
We develop the formal tools needed to construct helicity amplitudes for massive gravitino in N=1 SUGRA. We start by considering the helicity states for massive spin-3/2 particles, which involves the solutions of Rarita-Schwinger equation. These solutions are written in terms of the helicity bra-ket notation and are used then to derive the interactions of gravitino with matter and gauge supermultiplets within N=1 Supergravity. The corresponding interactions of goldstinos are discussed too, relying on the goldstino-gravitino equivalence theorem. Finally to appreciate the power of our methods we …
Gravitinos and hidden sector fields often cause a cosmological disaster in supersymmetric models. We find that a model with gravitational gauge mediation solves such a problem quite naturally. The mu-problem is also absent in the model. Moreover, the abundance of gravitinos explains correct amount of dark matter of the universe. The dark matter abundance can be calculated without detailed information on the thermal history of the universe such as the reheating temperature after inflation.
In the first stages of inflationary reheating, the temperature of the radiation produced by inflaton decays is typically higher than the commonly defined reheating temperature $T_{RH} \sim (Γ_ϕM_P)^{1/2}$ where $Γ_ϕ$ is the inflaton decay rate. We consider the effect of particle production at temperatures at or near the maximum temperature attained during reheating. We show that the impact of this early production on the final particle abundance depends strongly on the temperature dependence of the production cross section. For $\langle σv \rangle \sim T^n/M^{n+2}$, and for $n < 6$, any partic…
We discuss gravitino production from reheating in models where the splitting between particle and sparticle masses can be larger than TeV, as naturally arising in the context of split supersymmetry. We show that such a production typically dominates over thermal contributions arising from the interactions of gauginos, squarks and sleptons. We constrain the supersymmetry breaking scale of the relevant sector for a given reheat temperature. However the situation changes when the gravitinos dominate the Universe and decay before nucleosynthesis. We briefly describe prospects for a successful bary…
We investigate the superWIMP scenario in the framework of supersymmetry, in which the lightest supersymmetric particle is a stable gravitino. We consider slepton, sneutrino or neutralino being the next-lightest supersymmetric particle, and determine what superpartner masses are viable, applying cosmic-microwave background and electromagnetic and hadronic Big-Bang Nucleosythesis constraints.
In this paper, we revisit the gravitino dark matter scenario in the presence of the bilinear $R$-parity violating interaction. In particular, we discuss a consistency with the thermal leptogenesis. For a high reheating temperature required for the thermal leptogenesis, the gravitino dark matter tends to be overproduced, which puts a severe upper limit on the gluino mass. As we will show, a large portion of parameter space of the gravitino dark matter scenario has been excluded by combining the constraints from the gravitino abundance and the null results of the searches for the superparticles …
We consider the constraints that can be imposed on a wide class of Inflation models in modified gravity scenarios in which the Friedmann equation is modified by the inclusion of $ρ^2$ terms, where $ρ$ is the total energy density. In particular we obtain the reheating temperature and gravitino abundance associated with the end of inflation. Whereas models of chaotic inflation and natural inflation can easily avoid the conventional gravitino overproduction problem, we show that supersymmetric hybrid inflation models (driven by both F and D-terms) do not work in the $ρ^2$ dominated era. We also s…
We show that the gravitino contribution to (g-2)_μ is finite in many popular supergravity models, including no-scale supergravity and string and M-theory models. This contribution is greatly enhanced for very light gravitino masses, and leads to new upper bounds on the ratio of the smuon to the gravitino mass.
By using a string-inspired modular invariant supergravity, which was proved well to explain WMAP observations appropriately, a mechanism of supersymmetry breaking (SSB) and Gravitino Production just after the end of inflation are investigated. Supersymmetry is broken mainly by F-term of the inflaton superfield and the Goldstino is identified to be inflatino in this model, which fact is shown numerically. By using the canonically normalized and diagonalized scalars, the decay rates of these fields are calculated, for both the $T$ and $Y$ into gravitinos. Non-thermal production of gravitinos is …
By using a No-Scale Supergravity model, which was proved to explain WMAP observations appropriately, a mechanism of supersymmetry breaking and a preheating just after the end of inflation are investigated. Non-thermal production rate of gravitino is estimated as well as supersymmetry breaking mechanism numerically. The supersymmetry breaking is triggered by the inflaton superfield alone and the interchange of supersymmetry breaking fields does not occur in our model. By the instant preheating mechanism, the preheating temperature is calculated through the process where the inflaton decays into…
We extend our previous study of supersymmetric Higgs inflation in the context of no-scale supergravity and grand unification, to include models based on the flipped SU(5) and the Pati-Salam group. Like the previous SU(5) GUT model, these yield a class of inflation models whose inflation predictions interpolate between those of the quadratic chaotic inflation and Starobinsky-like inflation, while avoiding tension with proton decay limits. We further analyse the reheating process in these models, and derive the number of e-folds, which is independent of the reheating temperature. We derive the c…
We study the solution to the Polonyi problem where the Polonyi field weighs as $O(10{\rm TeV})$ and decays just before the primordial nucleosynthesis. It is shown that in spite of a large entropy production by the Polonyi field decay, one can naturally explain the present value of the baryon-to-entropy ratio, $n_B/s \sim (10^{-10}-10^{-11})$ if the Affleck-Dine mechanism for baryogenesis works. It is pointed out, however, that there is another cosmological problem related to the abundance of the lightest superparticles produced by the Polonyi decay.
Effects of the unstable gravitino on the big-bang nucleosynthesis (BBN) and its implications to particle cosmology are discussed. If the gravitino mass is smaller than \sim 20 TeV, lifetime of the gravitino becomes longer than \sim 1sec and its decay may spoil the success of the standard BBN. In order to avoid such a problem, upper bound on the reheating temperature after the inflation is obtained, which may be as low as \sim 10^{5-6} GeV. For a successful baryogenesis with such low reheating temeprature, a consistent scenario based on the large cutoff supergravity (LCSUGRA) hypothesis of supe…
We discuss the effects of the gravitino on the big-bang nucleosynthesis (BBN), paying particular attention to the hadronic decay mode of the gravitino. We will see that the hadronic decay of the gravitino significantly affect the BBN and, for the case where the hadronic branching ratio is sizable, very stringent upper bound on the reheating temperature after inflation is obtained.
Supersymmetric scenarios where the lightest superparticle (LSP) is the gravitino are an attractive alternative to the widely studied case of a neutralino LSP. A strong motivation for a gravitino LSP arises from the possibility of achieving higher reheating temperatures and thus potentially allow for thermal leptogenesis. The predictions for the primordial abundances of light elements in the presence of a late decaying next-to-LSP (NSLP) as well as the currently measured dark matter abundance allow us to probe the cosmological viability of such a scenario. Here we consider a gravitino-stau scen…
By using a No-Scale Supergravity model, which was proved well to explain WMAP observations appropriately, a mechanism of preheating just after the end of inflation is investigated. By using the canonically normalized and diagonalized scalars, the decay rates of these fields are calculated inflaton $S$ into gauge sector fields. The reheating temperature is estimated by both the stability condition of Boltzmann equation and the instant preheating mechanism. The both of reheating temperatures are almost the same order of magnitude $\sim O(10^{10})$ GeV. Because two mechanisms are completely indep…
We reconsider thermal production of gravitinos in the early universe, adding to previously considered 2 -> 2 gauge scatterings: a) production via 1 -> 2 decays, allowed by thermal masses; b) the effect of the top Yukawa coupling; c) a proper treatment of the reheating process. Our final result behaves physically (larger couplings give a larger rate) and is twice larger than previous results, implying e.g. a twice stronger constraint on the reheating temperature. Accessory results about (supersymmetric) theories at finite temperature and gravitino couplings might have some interest.
If local supersymmetry is the correct extension of the standard model of particle physics, then following Inflation the early universe would have been populated by gravitinos produced from scatterings in the hot plasma during reheating. Their abundance is directly related to the magnitude of the reheating temperature. The gravitino lifetime is fixed as a function of its mass, and for gravitinos with lifetimes longer than the age of the universe at redshift $z\simeq 2\times 10^{6}$ (or roughly $6\times 10^6{\rm s}$), decay products can produce spectral distortion of the cosmic microwave backgro…
Thermal leptogenesis requires the reheating temperature $T_R \gsim 3\times 10^{9}$ GeV, which contradicts a recently obtained constraint on the reheating temperature, $T_R \lsim 10^6$ GeV, for the gravitino mass of 100 GeV-10 TeV. This stringent constraint comes from the fact that the hadronic decays of gravitinos destroy very efficiently light elements produced by the Big-Bang nucleosynthesis. However, it is not applicable if the gravitino is the lightest supersymmetric particle (LSP). We show that this solution to the gravitino problem works for the case where the next LSP is a scalar charge…
We propose a consistent scenario of the evolution of the universe based on the large cutoff supergravity (LCSUGRA) hypothesis of supersymmetry breaking, where the gravitino and sfermion become as heavy a $\sim O(1-10 {\rm TeV})$. With such a heavy gravitino, baryon asymmetry of the universe can be generated by the non-thermal leptogenesis via an inflaton decay without conflicting the serious gravitino problem. We also see that, in the LCSUGRA scenario, relic density of the lightest superparticle becomes consistent with the WMAP value of the dark matter density in the parameter region required …
In the context of a conformal Supergravity (SUGRA) model in the Einstein frame, in which the (next to) minimal supersymmetric standard model can embedded naturally to produce chaotic inflation scenarios, we study properties of gravitino in the cases where it is stable or unstable. In the latter case, we demonstrate that for large dilaton scale factors there is an enhanced magnitude of the gravitino width, when it decays to neutralino dark matter, as compared with the standard SUGRA case. In this context, we discuss the associated consequences as far as Big Bang Nucleosynthesis constraints and …
Supersymmetric thermal leptogenesis with a hierarchical right-handed neutrino mass spectrum requires the mass of the lightest right-handed neutrino to be heavier than about 10^9 GeV. This is in conflict with the upper bound on the reheating temperature which is found by imposing that the gravitinos generated during the reheating stage after inflation do not jeopardize successful nucleosynthesis. In this paper we show that a solution to this tension is actually already incorporated in the framework, because of the presence of flat directions in the supersymmetric scalar potential. Massive right…
We present a realistic supergravity inflation model which is free from the overproduction of potentially dangerous relics in cosmology, namely moduli and gravitinos which can lead to the inconsistencies with the predictions of baryon asymmetry and nucleosynthesis. The radiative correction turns out to play a crucial role in our analysis which raises the mass of supersymmetry breaking field to intermediate scale. We pay a particular attention to the non-thermal production of gravitinos using the non-minimal Kahler potential we obtained from loop correction. This non-thermal gravitino production…
Gravitinos are generically produced by inflaton decays, which place tight constraints on inflation models as well as supersymmetry breaking scale. We revisit the gravitino production from decays of the inflaton and the supersymmetry breaking field, based on a chaotic inflation model suggested by the recent BICEP2 result. We study cosmological constraints on thermally and non-thermally produced gravitinos for a wide range of the gravitino mass, and show that there are only three allowed regions of the gravitino mass: $m_{3/2}\lesssim 16$eV, $m_{3/2}\simeq 10$--$1000$TeV and $m_{3/2}\gtrsim 10^{…
The excessive production of gravitinos in the early universe destroys the successful predictions of nucleosynthesis. The thermal generation of gravitinos after inflation leads to the bound on the reheating temperature, T_{RH}< 10^9 GeV. However, it has been recently realized that the non-thermal generation of gravitinos in the early universe can be extremely efficient and overcome the thermal production by several orders of magnitude, leading to much tighter constraints on the reheating temperature. In this paper, we first investigate some aspects of the thermal production of gravitinos, takin…
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 during reheating or a serious gravitino problem.
We revisit Higgs inflation in the framework of a minimal extension of the Standard Model gauge symmetry by a $U(1)_{B-L}$ factor. Various aspects are taken into account with particular focus on the role of the supersymmetry breaking (SUSY) scale and the cosmological constraints associated with the gravitino. The scalar potential of the model is considered in the context of no-scale supergravity consisting of the F-part constructed from the Kähler function, the D-terms and soft SUSY contributions. We investigate several limiting cases and by varying the SUSY scale from a few TeV up to intermedi…
Present data require a spectral index $n\gsim 0.95$ at something like 1-$σ$ level. If this lower bound survives it will constrain `new' and `modular' inflation models, while raising it to 1.00 would rule out all of these models plus many others. After inflation, gravitinos are created by the oscillating field until the `intermediate' epoch when the Hubble parameter falls below the gravitino mass, or reheating, whichever is earlier. In a wide range of parameter space, these gravitinos are more abundant than those from thermal collisions, leading to stronger cosmological constraints.
Gravitinos are a fundamental prediction of supergravity, their mass ($m_{G}$) is informative of the value of the SUSY breaking scale, and, if produced during reheating, their number density is a function of the reheating temperature ($T_{\text{rh}}$). As a result, constraining their parameter space provides in turn significant constraints on particles physics and cosmology. We have previously shown that for gravitinos decaying into photons or charged particles during the ($μ$ and $y$) distortion eras, upcoming CMB spectral distortions bounds are highly effective in constraining the $T_{\text{r…
We utilize a recently proposed cubic nilpotent superfield to realize inflation in supergravity with the minimal degrees of freedom: the inflaton, graviton, and massive gravitino. As an advantage, the resultant model is free from the catastrophic production of gravitinos due to its vanishing propagation speed. However, the model suffers from the standard gravitino problem, and its viability depends on the mass spectrum and the thermal history of the universe.
We discuss sneutrino inflation in the brane-world scenario. We work in the Randall-Sundrum type II brane-world, generalized with the introduction of the Gauss-Bonnet term, a correction to the effective action in string theories. We find that a viable inflationary model is obtained with a reheating temperature appropriate to lead to the right baryon asymmetry and render the gravitino safe for cosmology. In specific realizations we satisfy all the observational constaints without the unnaturally small Yukawa couplings required in other related approaches.
In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via …
For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenes…
We consider compactifications induced by the gravitino field of eleven dimensional supergravity. Such compactifications are not trivial in the sense that the gravitino profiles are not related to pure bosonic ones by means of a supersymmetry transformation. The basic property of such backgrounds is that they admit $ψ$-torsion although they have vanishing Riemann tensor. Thus, these backgrounds may be considered also as solutions of the teleparallel formulation of supergravity. We construct two classes of solutions, one with both antisymmetric three-form field, gravity and gravitino and one wit…
Braneworld modifications to the Friedmann expansion law can have an important effect on the cosmological evolution of the early universe. In particular, the primordial particle abundances crucially depend on the rate at which the universe expanded at early times. In this article, we study the production of stable and unstable gravitinos, both from thermal creation and from the decay of a heavy scalar, in the Randall-Sundrum II braneworld context. We conclude that, depending on the value of the 5D fundamental Planck mass, some of the usual standard cosmology constraints on the reheating tempera…
We examine a scenario in which the reheating temperature $T_R$ after inflation is so low that it is comparable to, or lower than, the freeze out temperature of ordinary WIMPs. In this case the dark matter relic abundance is reduced, thus relaxing the impact of the usually strong constraint coming from the requirement that the universe does not overclose. We first re-examine the dynamics of freezeout during reheating. Next we apply a Bayesian approach to study the parameter space of the MSSM with ten free parameters, the CMSSM and the singlino-dominated regions of the NMSSM. In each case we fin…
In general the gravitino mass and/or the soft supersymmetry breaking masses in the observable sector can be much larger than the TeV scale. Depending on the relation between the masses, new important channels for gravitino production in the early Universe can arise. Gravitinos with a mass above 50 TeV decay before big bang nucleosynthesis, which leads to relaxation of the well known bound on the reheating temperature $T_{\rm R} \leq 10^{10}$ GeV. However, if the heavy gravitinos are produced abundantly in the early Universe, their decay can alter the abundance of the lightest supersymmetric pa…
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…
We present supersymmetric scenarios with gravitino LSP and stau NLSP in the case of a non-standard model of cosmology with the addition of a dark component in the pre-BBN era. In the context of the standard model of cosmology, gravitino LSP has drawn quite some attention as it is a good candidate for dark matter. It is produced in scattering processes during reheating after inflation and from the decay of the stau. With a long lifetime, the stau decays during Big Bang Nucleosynthesis. It is strongly constrained by the abundance of light elements but can however address the known "BBN lithium p…
We study the phenomenology of generic supergravity models in which gravity mediation naturally competes with gauge mediation as the origin of supergravity-breaking. This class of hybrid models has been recently motivated in string inspired constructions and differs from usual gauge mediated supersymmetry breaking models in having messenger masses of order of the GUT scale. In these scenarios the gravitino can be the lightest supersymmetric particle in wide regions of the parameter space and therefore a potential candidate for dark matter. We investigate this possibility, imposing the WMAP boun…
We discuss the highlights of recent developments in no-scale supergravity and flipped SU(5), especially in the context of a very light gravitino scenario that may explain the puzzling CDF e+e+gamma+gamma+E_T,miss event. We update the status of both subjects and discuss the impact of the latest experimental constraints from LEP and the Tevatron. We also comment on a new form of cold dark matter that may solve this phenomenological `problem' of light gravitino models. [Lecture presented by D. V. Nanopoulos at the 34th International School of Subnuclear Physics "Effective theories and fundamental…
In supergravity theories with a very light gravitino, the gluino decays dominantly to a gluon and a gravitino. This results in a much larger missing $E_T$ for the multijet final states in hadronic colliders. We use the latest Tevatron data for the multijet final states to set a new absolute lower bound of 3.0 x 10^{-13} GeV for the light gravitino mass.
Supergravity embedding of the Standard Model of particle physics provides phenomenologically well-motivated and observationally viable inflationary scenarios. We investigate a class of inflationary models based on the superconformal framework of supergravity and discuss constraints from the reheating temperature, with the particular focus on the gravitino problem inherent in these scenarios. We point out that a large part of the parameter space within the latest BICEP/Keck 95\% confidence contour may have been excluded by the gravitino constraints, depending on the mass scale of the inflaton. …
