Ultra-slow-roll (USR) inflation is a new mode of inflation which corresponds to the occasions when the inflaton field must traverse an extremely flat part of the scalar potential, when the usual ...slow-roll (SR) fails. We investigate USR and obtain an estimate for how long it lasts, given the initial kinetic density of the inflaton. We also find that, if the initial kinetic density is small enough, USR can be avoided and the usual SR treatment is valid. This has important implications for inflection-point inflation.
Quartic hilltop inflation remains one of the most successful inflationary models. Yet, the expectations of early treatments of hilltop inflation would contradict the observations and render the model ...excluded. However, recent numerical treatment has demonstrated that quartic hilltop inflation actually fares well with observations. In this work, a fully analytic treatment of the model aims to dispel the mystery surrounding the behaviour of quartic hilltop inflation. The results obtained are in excellent agreement with numerical works on the subject, yet offer simple analytic formulas to calculate observables and easily test thereby quartic hilltop inflation, hopefully revealing information on the theoretical background.
Is the Big Rip unreachable? Dimopoulos, Konstantinos
Physics letters. B,
10/2018, Letnik:
785
Journal Article
Recenzirano
Odprti dostop
I investigate the repercussions of particle production when the Universe is dominated by a hypothetical phantom substance. I show that backreaction due to particle production prevents the density ...from shooting to infinity at a Big Rip, but instead forces it to stabilise at a large constant value. Afterwards there is a period of de-Sitter inflation. I speculate that this might lead to a cyclic Universe.
We introduce warm quintessential inflation and study it in the weak dissipative regime. We consider the original quintessential inflation model, which approximates quartic chaotic inflation at early ...times and thawing quartic inverse-power-law quintessence at present. We find that the model successfully accounts for both inflation and dark energy observations, while it naturally reheats the Universe, thereby overcoming a major problem of quintessential inflation model-building.
A
bstract
It is shown that dark energy can be obtained from the interplay of the Higgs boson and the inflaton. A key element is the realization that electroweak symmetry breaking can trigger a second ...phase of rolling of the inflaton, which, when provided with the appropriate couplings between the fields, can be sufficiently slow to source accelerated expansion in the late time Universe. The observed dark energy density is obtained without fine-tuning of parameters or initial conditions due to an intricate conspiracy of numbers related to inflation, gravity and electroweak physics.
The BICEP2 experiment has announced a signal for primordial gravity waves with tensor-to-scalar ratio r=0.2−0.05+0.071. There are two ways to reconcile this result with the latest Planck experiment ...2. One is by assuming that there is a considerable tilt of r, Tr, with a positive sign, Tr=dlnr/dlnk≳0.57−0.27+0.29 corresponding to a blue tilt for the tensor modes of order nT≃0.53−0.27+0.29, assuming the Planck experiment best-fit value for tilt of scalar power spectrum nS. The other possibility is to assume that there is a negative running in the scalar spectral index, dnS/dlnk≃−0.02 which pushes up the upper bound on r from 0.11 up to 0.26 in the Planck analysis assuming the existence of a tensor spectrum. Simple slow-roll models fail to provide such large values for Tr or negative runnings in nS1. In this note we show that a non-Bunch–Davies initial state for perturbations can provide a match between large field chaotic models (like m2ϕ2) with the latest Planck result 3 and BICEP2 results by accommodating either the blue tilt of r or the negative large running of nS.
PDF
