13,193 research outputs found
Adiabatic Spectra During Slowly Evolving
In general, for single field, the scale invariant spectrum of curvature
perturbation can be given by either its constant mode or its increasing mode.
We show that during slowly expanding or contracting, the spectrum of curvature
perturbation given by its increasing mode can be scale invariance. The
perturbation mode can be naturally extended out of horizon, and the amplitude
of perturbation is consistent with the observations. We briefly discuss the
implement of this scenario.Comment: 3 pages, 1 figure, arguments, discussions and Refs. added, to publish
in PL
Emergently Thermalized Islands in the Landscape
In this note, we point out that in the eternal inflation driven by the
metastable vacua of the landscape, it might be possible that some large and
local quantum fluctuations with the null energy condition violation can stride
over the barriers between different vacua and straightly create some islands
with radiation and matter in new vacua. Then these thermalized islands will
evolve with the standard cosmology. We show that such islands may be consistent
with our observable universe, while has some distinctly observable signals,
which may be tested in coming observations.Comment: 4 pages, 1 eps figure, contents added and discussions extended,
publish in PL
On Primordial Density Perturbation and Decaying Speed of Sound
The decaying speed of sound can lead to the emergence of the primordial
density perturbation in any expanding phase, even if the expansion is
decelerated. Recently, some proposals have been given to implement this
mechanism, in which it was found that the primordial spectrum of scalar
perturbation can be scale invariant. In this note, we will give more insights
for the details of this seeding mechanism.Comment: 3 pages, 2 eps figure, contents extended, refs. added, published
version
Design of a Cyclic Multiverse
Recently, it has been noticed that the amplification of the amplitude of
curvature perturbation cycle by cycle can lead to a cyclic multiverse scenario,
in which the number of universes increases cycle by cycle. However, this
amplification will also inevitably induce either the ultimate end of
corresponding cycle, or the resulting spectrum of perturbations inside
corresponding universe is not scale invariant, which baffles the existence of
observable universes. In this paper, we propose a design of a cyclic
multiverse, in which the observable universe can emerges naturally. The
significance of a long period of dark energy before the turnaround of each
cycle for this implementing is shown.Comment: 6 pages, 3 eps figures, v2: 1 eps figure added and some arguments
added, to published in PL
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