14525091
Inflationary non-Gaussianity from thermal fluctuations
We calculate the contribution of fluctuations with a thermal origin to the inflationary non-Gaussianity. We find that even a small component of radiation can lead to a large non-Gaussianity. We show that this thermal non-Gaussianity always has positive f(NL). We illustrate our result in the chain inflation model and the very weakly dissipative warm inflation model. We show that f(NL) similar to O(1) is general in such models. If we allow a modified equation of state, or some decoupling effects, a large thermal non-Gaussianity of order f(NL) > 5 or even f(NL) similar to 100 can be produced. We also show that the power spectrum of chain inflation should have a thermal origin. In the appendix, we give a clarification on the different conventions used in the literature related to the calculation of f(NL).
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.
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.
119110055
EMRI data analysis with a phenomenological waveform
Extreme mass ratio inspirals (EMRIs) (capture and inspiral of a compact stellar mass object into a Massive Black Hole (MBH)) are among the most interesting objects for the gravitational wave astronomy. It is a very challenging task to detect those sources with the accurate estimation parameters of binaries primarily due to a large number of the secondary maxima on the likelihood surface. Search algorithms based on the matched filtering require computation of the gravitational waveform hundreds of thousands of times, which is currently not feasible with the most accurate (faithful) models of EMRIs. Here we propose to use a phenomenological template family which covers a large range of EMRIs parameter space. We use these phenomenological templates to detect the signal in the simulated data and then, assuming a particular EMRI model, estimate the physical parameters of the binary. We have separated the detection problem, which is done in a model-independent way, from the parameter estimation. For the latter one, we need to adopt the model for inspiral in order to map phenomenological parameters onto the physical parameter characterizing EMRIs.
119257183
Observation of the decay $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{\pm}\pi^{\mp}+c.c.$
Using a sample of $1.06\times10^{8}$ $\psi(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{+}\pi^{-}+c.c.$ and $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{-}\pi^{+}+c.c.$. The branching fractions are measured to be $\mathcal{B}(\psi(3686) \rightarrow \Lambda\bar\Sigma^{+}\pi^{-} + c.c.)=(1.40\pm 0.03 \pm 0.13)\times10^{-4}$ and $\mathcal{B}(\psi(3686) \rightarrow \Lambda\bar\Sigma^{-}\pi^{+}+c.c.)=(1.54\pm 0.04 \pm 0.13)\times10^{-4}$, where the first errors are statistical and the second ones systematic.
18345543
A Measurement of the Primordial Power Spectrum from Maxima and Boomerang Data
Model-independent measurements of the primordial power spectrum of matter density fluctuations provide a unique probe of physics in the very early universe, and can provide powerful constraints on inflationary models. We parametrize the primordial power spectrum A2s(k) as an arbitrary function, and measure its binned amplitude from the cosmic microwave background radiation anisotropy (CMB) data from Maxima and Boomerang. We find that for a flat universe with A2s(k) = 1 (scale-invariant) for scales k < 0.001 h/Mpc, the primordial power spectrum deviates significantly from a scale-invariant HarrisonZeldovich spectrum. It has a drop in power at 0.001 h/Mpc < ∼ k < ∼ 0.01 h/Mpc, and a rise in power at 0.01 h/Mpc < ∼ k < ∼ 0.1 h/Mpc, with the general trend of less power on small scales compared to a scale-invariant power spectrum. Our results are consistent with large scale structure data, and seem to suggest that unusual physics may have occurred in the very early universe. At the dawn of the new millennium, the inflationary paradigm appears the most plausible solution to the problems of the standard cosmology, and consistent with all current observational data. However, we are still far from establishing a definitive model of inflation. There currently exists a broad range of inflationary models (Kolb 1997, Turner 1997), many of which appear consistent with observational data. Model-independent measurements of the primordial power spectrum of matter density fluctuations can provide unique and powerful constraints on inflationary models. Although it has been conventional to take the primordial power spectrum to be a featureless power law in analyzing cosmological data, there are both theoretical and observational reasons to allow the primordial power spectrum to be a free function.
124790807
ILC 3.2 km damping ring design based on the FODO cell
We report on a new design for an ILC 3.2 km damping ring, with 2 arcs based on the FODO cell and 2 straight sections that are nearly the same as the newest version of the 6.4 km ring DCO4. This new lattice requires fewer magnets and a lower RF voltage, and has a better dynamic aperture than DCO4 while maintaining flexibility in regard to the momentum compaction factor. So far, this design is the only one satisfying all the requirements for a 3.2 km ring. The work on the lattice design and the dynamic aperture study is presented in detail.
119242452
Unified dark fluid with constant adiabatic sound speed and cosmic constraints
As is known above 90% of the energy content in Universe is made of unknown dark component. Usually this dark fluid is separated into two parts: dark matter and dark energy. However, it may be a mixture of these two energy components, or just one exotic unknown fluid. This property is dubbed as dark degeneracy. With this motivation, in this paper, a unified dark fluid having constant adiabatic sound speed $c_s^2=\alpha$, which is in the range $[0,1]$, is studied. At first, via the energy conservation equation, its energy density, $\rho_d/\rho_{d0}=(1-B_s)+B_s a^{-3(1+\alpha)}$ where $B_s$ is related to integration constant from energy conservation equation as another model parameter, is presented. Then by using Markov Chain Monte Carlo method with currently available cosmic observational data sets which include type Ia supernova Union 2, baryon acoustic oscillation and WMAP 7-year data of cosmic background radiation, we show that small values of $\alpha$ are favored in this unified dark fluid model. Furthermore, we show that smaller values of $\alpha<10^{-5}$ are required to match matter (baryon) power spectrum from SDSS DR7.