Effects of thermal inflation on small scale density perturbations

Abstract

In cosmological scenarios with thermal inflation, extra eras of moduli matter domination, thermal inflation and flaton matter domination exist between primordial inflation and the radiation domination of Big Bang nucleosynthesis. During these eras, cosmological perturbations on small scales can enter and re-exit the horizon, modifying the power spectrum on those scales. The largest modified scale, k b , touches the horizon size when the expansion changes from deflation to inflation at the transition from moduli domination to thermal inflation. We analytically calculate the evolution of perturbations from moduli domination through thermal inflation and evaluate the curvature perturbation on the constant radiation density hypersurface at the end of thermal inflation to determine the late time curvature perturbation. Our resulting transfer function suppresses the power spectrum by a factor ∼ 50 at k ≫ k b , with k b corresponding to anywhere from megaparsec to subparsec scales depending on the parameters of thermal inflation. Thus, thermal inflation might be constrained or detected by small scale observations such as CMB distortions or 21cm hydrogen line observations. * heezoe@dgist.ac.kr 2

Cosmological signals of a mirror twin Higgs

“…The relation of this characteristic scale to present-day observables is easily done using the framework given in [55]. Let the subscripts a, b, c, d, e respectively correspond to the beginning of the first inflationary period, the end of that period, the beginning of the second inflationary period, the end of that period, and the beginning of radiation domination.…”

N-body simulations of structure formation in thermal inflation cosmologies

“…A suppression in the curvature power spectrum can be achieved e.g. when the first derivative of the inflaton potential (in one-field inflation models) has a discontinuity [6,12,14] or when a second inflationary stage is introduced (as in models of thermal inflation, see below) [13]. nCDM models, on the other hand, introduce non-standard DM mechanisms that modify the shape of the power spectrum during the evolution of the fluctuations in the radiation and matter domination epochs, while the primordial power spectrum is the standard scale-invariant one.…”

“…[16,19]) can potentially introduce new features into structure formation that deserve to be investigated in detail, and which could potentially leave signatures of thermal inflation in the large-scale structure of the Universe. Here, we investigate the non-linear evolution of structure formation in the thermal inflation scenario described in [13] by using high-resolution N-body simulations, highlighting the main differences with respect to the results found in nCDM, other non-standard inflation models and standard ΛCDM. We note that the impact of thermal inflation on structure formation was addressed recently in [42], by e.g.…”

Constraints on just enough inflation preceded by a thermal era

“…In models of thermal inflation invoked to solve the moduli problem [24][25][26] primordial inflation is followed by a later phase of 'thermal' inflation which is driven by the potential energy of a 'flaton' field trapped at the origin at the minimum of its thermal effective potential [24,25,27]. Density perturbations generated during the short later phase of thermal inflation influence the spectrum only on very small scales while the larger scale perturbations which influence the large scale structure and cosmic microwave background are largely generated during the earlier primordial inflation [28]. Since the flaton has thermal interactions one would expect that the flaton quanta would have a thermal Bose-Einstein distribution, which has so far not been considered.…”