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The domain wall problem of the Peccei–Quinn mechanism can be solved if the Peccei–Quinn symmetry is explicitly broken by a small amount. Domain walls decay into axions, which may account for dark matter of the universe. This scheme is however strongly constrained by overproduction of axions unless the phase of the explicit breaking term is tuned. We investigate the case where the universe is matter-dominated around the temperature of the MeV scale and domain walls decay during this matter dominated epoch. We show how the viable parameter space is expanded. [ABSTRACT FROM AUTHOR]

The large hierarchy between the Planck scale and the weak scale can be explained by the dynamical breaking of supersymmetry in strongly coupled gauge theories. Similarly, the hierarchy between the Planck scale and the energy scale of inflation may also originate from strong dynamics, which dynamically generate the inflaton potential. We present a model of the hidden sector which unifies these two ideas, i.e., in which the scales of inflation and supersymmetry breaking are provided by the dynamics of the same gauge group. The resultant inflation model is chaotic inflation with a fractional power-law potential in accord with the upper bound on the tensor-to-scalar ratio. The supersymmetry breaking scale can be much smaller than the inflation scale, so that the solution to the large hierarchy problem of the weak scale remains intact. As an intrinsic feature of our model, we find that the sgoldstino, which might disturb the inflationary dynamics, is automatically stabilized during inflation by dynamically generated corrections in the strongly coupled sector. This renders our model a field-theoretical realization of what is sometimes referred to as sgoldstino-less inflation. [ABSTRACT FROM AUTHOR]

Similarities between the gauge meditation of supersymmetry breaking and the QCD axion model suggest that they originate from the same dynamics. We present a class of models where supersymmetry and the Peccei–Quinn symmetry are simultaneously broken. The messengers that mediate the effects of these symmetry breakings to the Standard Model are identical. Since the axion resides in the supersymmetry breaking sector, the saxion and the axino are heavy. We show constraints on the axion decay constant and the gravitino mass. [ABSTRACT FROM AUTHOR]

We point out that the prediction of the minimal chaotic inflation model is altered if a scalar field takes a large field value close to the Planck scale during inflation due to a negative Hubble induced mass. In particular, we show that the inflaton potential is effectively flattened at a large inflaton field value in the presence of such a scalar field. The scalar field may be identified with the standard model Higgs field or super partners of standard model fermions. With such Hubble-induced flattening, we find that the minimal chaotic inflation model, especially the model with a quadratic potential, is consistent with recent observations of the cosmic microwave background fluctuation without modifying the inflation model itself. [ABSTRACT FROM AUTHOR]

We present composite models explaining the diphoton excess of mass around 750 GeV recently reported by the LHC experiments. [ABSTRACT FROM AUTHOR]

We discuss a possible answer to the fundamental question of why nature would actually prefer low-scale supersymmetry, but end up with a supersymmetry scale that is not completely natural. This question is inevitable if we postulate that low-energy supersymmetry is indeed realized in nature, despite the null observation of superparticles below a TeV at the Large Hadron Collider. As we argue in this paper, superparticles masses in the multi-TeV range can, in fact, be reconciled with the concept of naturalness by means of a cosmological selection effect—a selection effect based on the assumption of an exact discrete R -symmetry that is spontaneously broken by gaugino condensation in a pure supersymmetric Yang–Mills theory. In such theories, the dynamical scale of the Yang–Mills gauge interactions is required to be higher than the inflationary Hubble scale, in order to avoid the formation of domain walls. This results in a lower limit on the superparticle masses and leads us to conclude that, according to the idea of naturalness, the most probable range of superparticle masses is potentially located at the multi-TeV, if the inflationary Hubble rate is of O ( 10 14 ) GeV . Our argument can be partially tested by future measurements of the tensor fraction in the Cosmic Microwave Background fluctuations. [ABSTRACT FROM AUTHOR]

We consider a scenario where supersymmetry breaking, its mediation, and the cancellation of the theta parameter of S U (3) C are all caused by a single chiral multiplet. The string axion multiplet is a natural candidate of such a superfield. We show that the scenario provides a convincing basis of focus point gaugino mediation, where the electroweak scale is explained with a moderate tuning among the parameters of the theory. [ABSTRACT FROM AUTHOR]

We consider an initial condition problem in a nearly quadratic chaotic inflation model in supergravity. We introduce shift symmetry breaking not only in the superpotential but also in the Kahler potential. In this model the inflaton potential is nearly quadratic for inflaton field values around the Planck scale, but deviates from the quadratic one for larger field values. As a result, the prediction on the tensor-to-scalar ratio can be smaller than that of a purely quadratic model. Due to the shift symmetry breaking in the Kahler potential, the inflaton potential becomes steep for large inflaton field values, which may prevent inflation from naturally taking place in a closed universe. We estimate an upper bound on the magnitude of the shift symmetry breaking so that inflation takes place before a closed universe with a Planck length size collapses, which yields a lower bound on the tensor-to-scalar ratio, r ≳ 0.1 . [ABSTRACT FROM AUTHOR]

We construct a natural inflation model in supergravity where the inflaton is identified with a modulus field possessing a shift symmetry. The superpotential for the inflaton is generated by meson condensation due to strong dynamics with deformed moduli constraints. In contrast to models based on gaugino condensation, the inflaton potential is generated without R -symmetry breaking and hence does not depend on the gravitino mass. Thus, our model is compatible with low scale supersymmetry. [ABSTRACT FROM AUTHOR]

The observation of the B-mode in the cosmic microwave background radiation combined with the so-called Lyth bound suggests the trans-Planckian variation of the inflaton field during inflation. Such a large variation generates concerns over inflation models in terms of the effective field theory below the Planck scale. If the inflaton resides in a Riemann surface and the inflaton potential is a multivalued function of the inflaton field when it is viewed as a function on a complex plane, the Lyth bound can be satisfied while keeping field values in the effective field theory within the Planck scale. We show that a multivalued inflaton potential can be realized starting from a single-valued Lagrangian of the effective field theory below the Planck scale. [ABSTRACT FROM AUTHOR]

Abstract: The BICEP2 collaboration has recently reported a large tensor fluctuation in the cosmic microwave background, which suggests chaotic inflation models. In this letter, we reconsider the chaotic inflation model in the supergravity. We introduce a non-holomorphic shift-symmetry breaking parameter, which we expect to exist in general, and discuss its effect on the inflaton dynamics. We show that the model predicts a sizable deviation from the original chaotic inflation model and the predicted tensor fluctuation can lie between the BICEP2 result and the upper bound given by the Planck experiment with a small shift-symmetry breaking parameter. The model is characterized by only two parameters, which yields predictability and testability in future experiments. [Copyright &y& Elsevier]

Abstract: The measurement of a large tensor-to-scalar ratio by the BICEP2 experiment, , severely restricts the landscape of viable inflationary models and shifts attention once more towards models featuring large inflaton field values. In this context, chaotic inflation based on a fractional power-law potential that is dynamically generated by the dynamics of a strongly coupled supersymmetric gauge theory appears to be particularly attractive. We revisit this class of inflation models and find that, in the light of the BICEP2 measurement, models with a non-minimal gauge group behind the dynamical model seem to be disfavored, while the model with the simplest group, i.e. , is consistent with all results. We also discuss how the dynamical model can be distinguished from the standard chaotic inflation model based on a quadratic inflaton potential. [Copyright &y& Elsevier]

Abstract: The Polonyi field is a necessary ingredient in any viable scenario of gravity mediated supersymmetry breaking. However, it is known that the presence of the Polonyi field leads to several serious cosmological problems, which are collectively referred to as the Polonyi problem. We show that the Polonyi problem can be solved if the Polonyi field couples to a pseudo-modulus in the superpotential and this pseudo-modulus has a large field expectation value during inflation. To illustrate our idea, we construct an explicit model which can be readily connected to scenarios of gravity mediation. The generation of the mass parameters contained in our model by strong gauge dynamics is also commented on. [Copyright &y& Elsevier]

Abstract: Models of chaotic inflation with a fractional power-law potential are not only viable but also testable in the foreseeable future. We show that such models can be realized in simple strongly coupled supersymmetric gauge theories. In these models, the energy scale during inflation is dynamically generated by the dimensional transmutation due to the strong gauge dynamics. Therefore, such models not only explain the origin of the fractional power in the inflationary potential but also provide a reason why the energy scale of inflation is much smaller than the Planck scale. [Copyright &y& Elsevier]

Abstract: The recently observed mass ∼ 125 GeV for the Higgs boson suggests a high-energy scale SUSY breaking, above . It is, however, very puzzling why nature chooses such a high-energy scale for the SUSY breaking, if the SUSY is a solution to the hierarchy problem. We show that the pure gravity mediation provides us with a possible solution to this puzzle if the topological inflation is the last inflation in the early universe. We briefly discuss a chaotic inflation model in which a similar solution can be obtained. [Copyright &y& Elsevier]

Detection of electron recoils by dark matter (DM) may reveal the structure of the dark sector. We consider a scenario where a heavier DM particle inelastically scatters off an electron and is converted into a lighter DM particle. A small mass difference between the two DM particles is transferred into electron recoil energy. We investigate the DM-electron interaction mediated by a massive dark photon and evaluate the inelastic DM scattering rate, taking account of the atomic structure. It is found that the scattering rate is significantly enhanced because of the small mass splitting, which allows for a small momentum transfer matched with the size of the electron wave function. We show that there exists a viable parameter space which explains the excess of electron recoil events around 2-3 keV recently reported by the XENON1T experiment. [ABSTRACT FROM AUTHOR]