Search Publications
Matter power spectra in viable f (R) gravity models with massive neutrinos
Geng, Chao-Qiang; Lee, Chung-Chi; Shen, Jia-Liang
We investigate the matter power spectra in the power law and exponential types of viable f (R) theories along with massive neutrinos. The enhancement of the matter power spectrum is found to be a generic feature in these models. In particular, we show that in the former type, such as the Starobinsky model, the spectrum is magnified much larger tha…
The importance of being warm (during inflation)
Rosa, João G.; Ramos, Rudnei O.; Bartrum, Sam +3 more
The amplitude of primordial curvature perturbations is enhanced when a radiation bath at a temperature T>H is sustained during inflation by dissipative particle production, which is particularly significant when a non-trivial statistical ensemble of inflaton fluctuations is also maintained. Since gravitational modes are oblivious to dissipative…
Non-Bunch-Davis initial state reconciles chaotic models with BICEP and Planck
Ashoorioon, Amjad; Dimopoulos, Konstantinos; Sheikh-Jabbari, Mohammad M. +1 more
The BICEP2 experiment has announced a signal for primordial gravity waves with tensor-to-scalar ratio r =0.2-0.05+0.07[1]. 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 = dln r /…
Coleman-Weinberg inflation in light of Planck
Barenboim, Gabriela; Chun, Eung Jin; Lee, Hyun Min
We revisit a single field inflationary model based on Coleman-Weinberg potentials. We show that in small field Coleman-Weinberg inflation, the observed amplitude of perturbations needs an extremely small quartic coupling of the inflaton, which might be a signature of radiative origin. However, the spectral index obtained in a standard cosmological…
Standard Clock in primordial density perturbations and cosmic microwave background
Namjoo, Mohammad Hossein; Chen, Xingang
Standard Clocks in the primordial epoch leave a special type of features in the primordial perturbations, which can be used to directly measure the scale factor of the primordial universe as a function of time a (t), thus discriminating between inflation and alternatives. We have started to search for such signals in the Planck 2013 data using the…
Observational constraints on variable equation of state parameters of dark matter and dark energy after Planck
Xu, Lixin; Kumar, Suresh
In this paper, we study a cosmological model in general relativity within the framework of spatially flat Friedmann-Robertson-Walker space-time filled with ordinary matter (baryonic), radiation, dark matter and dark energy, where the latter two components are described by Chevallier-Polarski-Linder equation of state parameters. We utilize the obse…
Testing quantum gravity effects with latest CMB observations
Wang, Yi; Cai, Yi-Fu
Inspired by quantum gravitational physics, the approach of non-commutative (NC) phase space leads to a modified dispersion relation of gravitational waves. This feature, if applied to the very early universe, gives rise to a modified power spectrum of primordial tensor perturbations with a suppression of power on large scales. We confront this phe…
Chaotic inflation with right-handed sneutrinos after Planck
Nakayama, Kazunori; Yanagida, Tsutomu T.; Takahashi, Fuminobu
We propose a chaotic inflation model in which the lightest right-handed sneutrino serves as the inflaton and the predicted values of the spectral index and tensor-to-scalar ratio are consistent with the Planck data. Interestingly, the observed magnitude of primordial density perturbations is naturally explained by the inflaton mass of order 10
Measuring growth index in a Universe with sterile neutrinos
Zhang, Jing-Fei; Zhang, Xin; Li, Yun-He
Consistency tests for the general relativity (GR) can be performed by constraining the growth index γ using the measurements of redshift-space distortions (RSD) in conjunction with other observations. In previous studies, deviations from the GR expected value of γ ≈ 0.55 at the 2-3σ level were found. In this work, we reconsider the measurement of …
Probing the primordial Universe from the low-multipole CMB data
Cheng, Cheng; Huang, Qing-Guo
Since the temperature fluctuations in the cosmic microwave background (CMB) on large-angular scales probe length scales that were super-horizon sized at photon decoupling and hence insensitive to microphysical processes, the low-multipole CMB data are supposed to be a good probe to the physics of the primordial Universe. In this letter we will con…