118450702
Multi-stream inflation in a landscape
There are hidden observables for inflation, such as features localized in position space, which do not manifest themselves when only one inflation trajectory is considered. To address this issue, we investigate inflation dynamics in a landscape mimicked by a random potential. We calculate the probability for bifurcation of the inflation trajectory in multi-stream inflation. Depending on the shape of the random bumps and the distance between bumps in the potential, there is a phase transition: on one side of the critical curve in parameter space isocurvature fluctuation are exponentially amplified and bifurcation becomes very probable. On the other side bifurcation is dominated by a random walk where bifurcations are less likely to happen.
2921220
Non-Gaussianity, isocurvature perturbation, gravitational waves, and a no-go theorem for the isocurvaton
We investigate the isocurvaton model, in which the isocurvature perturbation plays a role in suppressing the curvature perturbation, and large non-Gaussianity and gravitational waves can be produced with no isocurvature perturbation for dark matter. We show that in the slow-roll noninteracting multifield theory, the isocurvaton mechanism cannot be realized. This result can also be generalized to most of the studied models with generalized kinetic terms. We also study the implications for the curvaton model. We show that there is a combined constraint for curvaton on non-Gaussianity, gravitational waves, and isocurvature perturbation. The technique used in this paper can also help to simplify some calculations in the mixed inflaton and curvaton models. We also investigate the possibility of producing large negative non-Gaussianity and nonlocal non-Gaussianity in the curvaton model.
118533325
Quasi-Single Field Inflation and Non-Gaussianities
In quasi-single field inflation models, massive isocurvature modes, that are coupled to the inflaton and have mass of order the Hubble parameter, can have nontrivial impacts on density perturbations, especially non-Gaussianities. We study a simple example of quasi-single field inflation in terms of turning inflaton trajectory. Large bispectra with a one-parameter family of novel shapes arise, lying between the well-known local and equilateral shape. The trispectra can also be very large and its magnitude tNL can be much larger than fNL2.
119112752
CMB statistical anisotropies of classical and quantum origins
We examine the impact of different anisotropic relics on inflation, in particular the predictions on the density perturbations. These relics can be the source of the large scale anomalies in the cosmic microwave background. There are two different types of background relics, one from the matter sector and the other purely from the metric. Although the angular-dependence of the statistical anisotropy in both cases are degenerate, the scale-dependence are observationally distinctive. In addition, we demonstrate that non-Bunch-Davies vacuum states can extend the statistical anisotropy to much shorter scales, and leave a scale-dependence that is insensitive to the different backgrounds but sensitive to the initial quantum state.
17457342
Curvaton dynamics and the non-linearity parameters in the curvaton model
We investigate the curvaton dynamics and the non-linearity parameters in the curvaton model with a potential slightly deviating from the quadratic form in detail. The non-linearity parameter gNL will show up due to the curvaton self-interaction. We also point out that the leading order of the non-quadratic term in the curvaton potential can be negative, for example in the axion-type curvaton model. If a large positive gNL is detected, the axion-type curvaton model will be preferred.
119270914
Quadra-Spectrum and Quint-Spectrum from Inflation and Curvaton Models
We calculate the quadra-spectrum and quint-spectrum, corresponding to five and six point correlation functions of the curvature perturbation. For single field inflation with standard kinetic term, the quadra-spectrum and quint-spectrum are small, which are suppressed by slow roll parameters. The calculation can be generalized to multiple fields. When there is no entropy perturbation, the quadra-spectrum and quint-spectrum are suppressed as well. With the presence of entropy perturbation, the quadra-spectrum and quint-spectrum can get boosted. We illustrate this boost in the multi-brid inflation model. For the curvaton scenario, the quadra-spectrum and quint-spectrum are also large in the small r limit. We also calculate representative terms of quadra-spectrum and quint-spectrum for inflation with generalized kinetic terms, and estimate their order of magnitude for quasi-single field inflation.
120221743
Asymmetric Hopf bifurcation for proton beams with electron cooling
We observed maintained longitudinal limiting cycle oscillations, which grew rapidly once a critical threshold in the relative velocity between the proton beam and the cooling electrons was exceeded. The threshold for the bifurcation of a fixed point into a limit cycle, also known as a Hopf bifurcation, was found to be asymmetric with respect to the relative velocity. This asymmetry of Hopf bifurcation was found to be related to the electron beam alignment with respect to the stored proton beam.
119387792
Model-independent Constraints on Dark Energy Density from Flux-averaging Analysis of Type Ia Supernova Data
We reconstruct the dark energy density X(z) as a free function from current Type Ia supernova (SN Ia) data, together with the cosmic microwave background (CMB) shift parameter from CMB data from the Wilkinson Microwave Anisotropy Probe (WMAP), Cosmic Background Imager (CBI), and Arcminute Cosmology Bolometer Array Receiver (ACBAR), and the large-scale structure (LSS) growth factor from the Two-Degree Field (2dF) galaxy survey data. We parameterize X(z) as a continuous function, given by interpolating its amplitudes at equally spaced z-values in the redshift range covered by SN Ia data, and a constant at larger z [where X(z) is only weakly constrained by CMB data]. We assume a flat universe and use the Markov Chain Monte Carlo (MCMC) technique in our analysis. We find that the dark energy density X(z) is constant for 0<~z<~0.5 and increases with redshift z for 0.5<~z<~1 at a 68.3% confidence level, but is consistent with a constant at a 95% confidence level. For comparison, we also give constraints on a constant equation of state for the dark energy. Flux averaging of SN Ia data is required to yield cosmological parameter constraints that are free of the bias induced by weak gravitational lensing. We set up a consistent framework for flux-averaging analysis of SN Ia data, based on the work of Wang. We find that flux averaging of SN Ia data leads to slightly lower m and smaller time variation in X(z). This suggests that a significant increase in the number of SNe Ia from deep SN surveys on a dedicated telescope is needed to place a robust constraint on the time dependence of the dark energy density.
125751010
Energy and centrality dependence of the contribution from leading particles to charged-particle pseudorapidity distribution
116531868
Status, new development and upgrading program at HIRFL
The operation status and new development including the accelerator and experimental stations of HIRFL facility in the last years, and the upgrading program for the next five years are presented. The new completed radioactive beam line RIBLL, the new axial injection system and the new central region for the injector, the ECR ion source development and the new frame of control system are given in some details. The new project CSR is also presented with its main parameters. A upgrading program is under studying to meet the requirement of RIBLL and CSR towards radioactive beam researches.
122885169
Plausible double inflation
Abstract It is likely that extended inflation is followed by an epoch of slowroll inflation. Such a sequence of events may lead to a very interesting perturbation spectrum with significant power on the scale of the transition between the extended and slowroll phase, superimposed upon a power-law spectrum with deviations from the Harrison-Zel'dovich slope. Normalization of the spectra above and below the transition scale is expected to differ.