54,617 research outputs found
Relic Vector Field and CMB Large Scale Anomalies
We study the most general effects of relic vector fields on the inflationary
background and density perturbations. Such effects are observable if the number
of inflationary e-folds is close to the minimum requirement to solve the
horizon problem. We show that this can potentially explain two CMB large scale
anomalies: the quadrupole-octopole alignment and the quadrupole power
suppression. We discuss its effect on the parity anomaly. We also provide
analytical template for more detailed data comparison.Comment: 15 pages, v4, references added, some comments revised, JCAP versio
Non-Bunch-Davies Anisotropy
We introduce a generic mechanism that can extend the effects of relic
anisotropies at the beginning of inflation to relatively much shorter scales in
density perturbations. This is induced by non-Bunch-Davies states of the
quantum fluctuations, and can show up in the non-oscillatory components of the
density perturbations. This mechanism works for general forms of anisotropies,
and, to illustrate it, we use an example of relic vector field. The detailed
scale-dependence of these anisotropies can be used to probe the initial quantum
state of our universe.Comment: 10 page
Inflation with Holographic Dark Energy
We investigate the corrections of the holographic dark energy to inflation
paradigm. We study the evolution of the holographic dark energy in the
inflationary universe in detail, and carry out a model-independent analysis on
the holographic dark energy correction to the primordial scalar power spectrum.
It turns out that the corrections generically make the spectrum redder. To be
consistent with the experimental data, there must be a upper bound on the
reheating temperature. We also discuss the corrections due to different choices
of the infrared cutoff.Comment: 15 pages, 3 figures, v2: references added, a fast-roll discussion
added. v3: typos corrected. v4: final version to appear in NP
Performance of a Multiple-Access DCSK-CC System over Nakagami- Fading Channels
In this paper, we propose a novel cooperative scheme to enhance the
performance of multiple-access (MA) differential-chaos-shift-keying (DCSK)
systems. We provide the bit-error-rate (BER) performance and throughput
analyses for the new system with a decode-and-forward (DF) protocol over
Nakagami- fading channels. Our simulated results not only show that this
system significantly improves the BER performance as compared to the existing
DCSK non-cooperative (DCSK-NC) system and the multiple-input multiple-output
DCSK (MIMO-DCSK) system, but also verify the theoretical analyses. Furthermore,
we show that the throughput of this system approximately equals that of the
DCSK-NC system, both of which have prominent improvements over the MIMO-DCSK
system. We thus believe that the proposed system can be a good framework for
chaos-modulation-based wireless communications.Comment: 4 pages, 5 figures, accepted, IEEE ISCAS, 201
Inflationary NonGaussianity from Thermal Fluctuations
We calculate the contribution of the fluctuations with the thermal origin to
the inflationary nonGaussianity. We find that even a small component of
radiation can lead to a large nonGaussianity. We show that this thermal
nonGaussianity always has positive . We illustrate our result in
the chain inflation model and the very weakly dissipative warm inflation model.
We show that is general in such models. If we allow
modified equation of state, or some decoupling effects, the large thermal
nonGaussianity of order or even can be
produced. We also show that the power spectrum of chain inflation should have a
thermal origin. In the Appendix A, we made a clarification on the different
conventions used in the literature related to the calculation of .Comment: 20 pages, 1 figure. v2, v3: references and acknowledgments update
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