Baryon Isocurvature Fluctuations Research Articles

Leptogenesis via inflaton mass terms in nonminimally coupled inflation

We consider a model of baryogenesis based on adding lepton number-violating quadratic mass terms to the inflaton potential of a non-minimally coupled inflation model. The $L$-violating mass terms generate a lepton asymmetry in a complex inflaton field via the mass term Affleck-Dine mechanism, which is transferred to the Standard Model (SM) sector when the inflaton decays to right-handed (RH) neutrinos. The model is minimal in that it requires only the SM sector, RH neutrinos, and a non-minimally coupled inflaton sector. We find that baryon isocurvature fluctuations can be observable in metric inflation but are negligible in Palatini inflation. The model is compatible with reheating temperatures that may be detectable in the observable primordial gravitational waves predicted by metric inflation.

Affleck-Dine inflation

The Affleck-Dine mechanism in its simplest form provides baryogenesis from the out-of-equilibrium evolution of a complex scalar field with a simple renormalizable potential. We show that such a model, supplemented by nonminimal coupling to gravity, can also provide inflation, consistent with Planck constraints, simultaneously with the generation of the baryon asymmetry. The predictions of the model include significant tensor-to-scalar ratio and possibly baryon isocurvature fluctuations. The reheating temperature is calculable, making the model fully predictive. We require color triplet scalars for reheating and transfering the primordial baryon asymmetry to quarks; these could be observable at colliders. They can also be probed at higher scales by searches for quark compositeness in dijet angular distributions, and flavor-changing neutral current effects.

Flat direction inflation with running kinetic term and baryogenesis

We consider a possibility that one of the flat directions in the minimal supersymmetric standard model plays the role of the inflaton field and realizes large-field inflation. This is achieved by introducing a generalized shift symmetry on the flat direction, which enables us to control the inflaton potential over large field values. After inflation, higher order terms allowed by the generalized shift symmetry automatically cause a helical motion of the field to create the baryon number of the universe, while baryonic isocurvature fluctuations are suppressed.

Differentiating CDM and baryon isocurvature models with 21 cm fluctuations

We discuss how one can discriminate models with cold dark matter (CDM) and baryon isocurvature fluctuations. Although current observations such as cosmic microwave background (CMB) can severely constrain the fraction of such isocurvature modes in the total density fluctuations, CMB cannot differentiate CDM and baryon ones by the shapes of their power spectra. However, the evolution of CDM and baryon density fluctuations are different for each model, thus it would be possible to discriminate those isocurvature modes by extracting information on the fluctuations of CDM/baryon itself. We discuss that observations of 21 cm fluctuations can in principle differentiate these modes and demonstrate to what extent we can distinguish them with future 21 cm surveys. We show that, when the isocurvature mode has a large blue-tilted initial spectrum, 21 cm surveys can clearly probe the difference.

Constraints on moduli cosmology from the production of dark matter and baryon isocurvature fluctuations

We set constraints on moduli cosmology from the production of dark matter---radiation and baryon---radiation isocurvature fluctuations through modulus decay, assuming the modulus remains light during inflation. We find that the moduli problem becomes worse at the perturbative level as a significant part of the parameter space ${m}_{\ensuremath{\sigma}}$ (modulus mass)---${\ensuremath{\sigma}}_{\mathrm{inf}}$ (modulus vacuum expectation value at the end of inflation) is constrained by the nonobservation of significant isocurvature fluctuations. We discuss in detail the evolution of the modulus vacuum expectation value and perturbations, in particular, the consequences of Hubble scale corrections to the modulus potential, and the stochastic motion of the modulus during inflation. We show, in particular, that a high modulus mass scale ${m}_{\ensuremath{\sigma}}\ensuremath{\gtrsim}100\text{ }\text{ }\mathrm{TeV}$, which allows the modulus to evade big bang nucleosynthesis constraints is strongly constrained at the perturbative level. We find that generically, solving the moduli problem requires the inflationary scale to be much smaller than ${10}^{13}\text{ }\text{ }\mathrm{GeV}$.

Non-Gaussianity and baryonic isocurvature fluctuations in the curvaton scenario

We discuss non-Gaussianity and baryonic isocurvature fluctuations in the curvaton scenario, assuming that the baryon asymmetry of the universe originates only from the decay products of the inflaton. When large non-Gaussianity is realized in such a scenario, non-vanishing baryonic isocurvature fluctuations can also be generated unless the baryogenesis occurs after the decay of the curvaton. We calculate the non-linearity parameter fNL and the baryonic isocurvature fluctuations, taking account of the primordial fluctuations of both the inflaton and the curvaton. We show that, although current constraints on isocurvature fluctuations are severe, the non-linearity parameter can be large as fNL∼O(10–100) without conflicting with the constraints.

Isocurvature fluctuations in the Affleck–Dine mechanism and constraints on inflationmodels

We argue that, in the Affleck–Dine mechanism, baryonic isocurvature fluctuations aregenerated in most inflation models in supergravity. The inflationary scale and a reheatingtemperature are constrained in order not to induce too large baryonic isocurvaturefluctuations. In particular, high-scale inflation models with high reheating temperatures aredisfavored in this context.

Sneutrino condensate source for density perturbations, leptogenesis, and low reheat temperature.

We bring together some known ingredients beyond the standard model physics that can explain the hot big bang model with the observed baryon asymmetry and also the fluctuations in the cosmic microwave background radiation with a minimal set of assumptions. We propose an interesting scenario where the inflaton energy density is dumped into an infinitely large extra dimension. Instead of the inflaton it is the right handed sneutrino condensate, which is acquiring a nonzero vacuum expectation value during inflation, whose fluctuations are responsible for the density perturbations seen in the cosmic microwave background radiation with a spectral index n(s) approximately 1. The decay of the condensate is explaining the reheating of the Universe with a temperature, T(rh)< or =10(9) GeV, and the baryon asymmetry of order one part in 10(10) with no baryon-isocurvature fluctuations.

Observable Isocurvature Fluctuations from the Affleck-Dine Condensate

In D-term inflation models, Affleck-Dine baryogenesis produces baryonic isocurvature fluctuations. In most cases the Affleck-Dine condensate is unstable with respect to collapse to B-balls, which can transform the baryon number perturbations into perturbations in the number of dark matter neutralinos. The requirement that the deviation of the adiabatic perturbations from scale invariance is not too large imposes a lower bound on the magnitude of the isocurvature fluctuations. In general this is larger than about ${10}^{\ensuremath{-}4}\phantom{\rule{0ex}{0ex}}times$ the adiabatic perturbation, and, for the particular case of late decaying B-balls, larger than about ${10}^{\ensuremath{-}2}\phantom{\rule{0ex}{0ex}}times$ the adiabatic perturbation, which should be observable by MAP and PLANCK.

Baryon isocurvature fluctuations at small scales and baryonic dark matter.

A model of baryogenesis is described which gives rise to fluctuations in baryon number that are large on small scales but of low amplitude on large scales. This provides a mechanism for primordial blackhole formation, and allows the possibility of a critical density of dark matter in baryonic (and antibaryonic) form. Since high-density regions naturally possess both signs of baryonic excess, our model also predicts a small fraction of the mass density of the Universe to be in the form of compact antibaryonic regions. These objects may be observable via a redshifted annihilation feature in the diffuse extragalactic $\ensuremath{\gamma}$-ray background, as both steady sources of $\ensuremath{\gamma}$-ray radiation and annihilation-powered $\ensuremath{\gamma}$-ray bursters at cosmological distances, by a distortion of the spectrum of the 3K background radiation, or by the presence of antihelium nuclei as a rare component of high-energy cosmic rays.