118462930
A Theory of a Spot
We present a simple inflationary scenario that can produce arbitrarily large spherical underdense or overdense regions embedded in a standard Λ cold dark matter paradigm, which we refer to as bubbles. We analyze the effect such bubbles would have on the Cosmic Microwave Background (CMB). For super-horizon sized bubble in the vicinity of the last scattering surface, a signal is imprinted onto CMB via a combination of Sach-Wolfe and an early integrated Sach-Wolfe (ISW) effects. Smaller, sub-horizon sized bubbles at lower redshifts (during matter domination and later) can imprint secondary anisotropies on the CMB via Rees-Sciama, late-time ISW and Ostriker-Vishniac effects. Our scenario, and arguably most similar inflationary models, produce bubbles which are over/underdense in potential: in density such bubbles are characterized by having a distinct wall with the interior staying at the cosmic mean density. We show that such models can potentially, with only moderate fine tuning, explain the cold spot, a non-Gaussian feature identified in the Wilkinson Microwave Anisotropy Probe (WMAP) data by several authors. However, more detailed comparisons with current and future CMB data are necessary to confirm (or rule out) this scenario.
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.
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.
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.
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.
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.
119276209
Planck priors for dark energy surveys
Although cosmic microwave background anisotropy data alone cannot constrain simultaneously the spatial curvature and the equation of state of dark energy, CMB data provide a valuable addition to other experimental results. However computing a full CMB power spectrum with a Boltzmann code is quite slow; for instance if we want to work with many dark energy and/or modified gravity models, or would like to optimize experiments where many different configurations need to be tested, it is possible to adopt a quicker and more efficient approach. In this paper we consider the compression of the projected Planck cosmic microwave background data into four parameters, R (scaled distance to last scattering surface), l{sub a} (angular scale of sound horizon at last scattering), {omega}{sub b}h{sup 2} (baryon density fraction) and n{sub s} (powerlaw index of primordial matter power spectrum), all of which can be computed quickly. We show that, although this compression loses information compared to the full likelihood, such information loss becomes negligible when more data is added. We also demonstrate that the method can be used for canonical scalar-field dark energy independently of the parametrization of the equation of state, and discuss how this method should be used for other kindsmore » of dark energy models.« less
17010406
A comparative study between eruptive X-class flares associated with coronal mass ejections and confined X-class flares
We examine the two kinds of major energetic phenomena that occur in the solar atmosphere: eruptive and confined events. The former describes flares with associated coronal mass ejections (CMEs), while the latter denotes flares without associated CMEs. We find that about 90% of X-class flares are eruptive, but the remaining 10% are confined. To probe why the largest energy releases could be either eruptive or confined, we investigate four X-class events from each of the two types. Both sets of events are selected to have very similar intensities (X1.0 to X3.6) and duration (rise time under 13 minutes and decay time over 9 minutes) in soft X-ray observations, to reduce any bias due to flare size on CME occurrence. We find that the occurrence of eruption (or confinement) is sensitive to the displacement of the location of the energy release, defined as the distance between the flare site and the flux-weighted magnetic center of the source active region. The displacement is 6-17 Mm for confined events but as large as 22-37 Mm for eruptive events. This means that confined events occur closer to the magnetic center, while the eruptive events tend to occur close to the edge of active regions. We use the potential field source-surface model to infer the coronal magnetic field above the source active regions and calculate the flux ratio of low ( 7.1). These results imply that a stronger overlying arcade field may prevent energy releases in the low corona from being eruptive, resulting in flares, but without CMEs.
1190941
Higher moments of net proton multiplicity distributions at RHIC.
We report the first measurements of the kurtosis (κ), skewness (S), and variance (σ2) of net-proton multiplicity (Np-Np) distributions at midrapidity for Au+Au collisions at square root of s(NN)=19.6, 62.4, and 200 GeV corresponding to baryon chemical potentials (μB) between 200 and 20 MeV. Our measurements of the products κσ2 and Sσ, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the square root of s(NN) dependence of κσ2. From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for μB below 200 MeV.
135660011
Hybrid photodiode tube
We report the first test results on a new breed of light detector based on a photocathode followed by a silicon diode working in the bombarding mode.
1288334
Model-independent measurement of the primordial power spectrum
In inflationary models with minimal amount of gravity waves, the primordial power spectrum of density fluctuations, AS2(k), together with the basic cosmological parameters, completely specify the predictions for the cosmic microwave background (CMB) anisotropy and large scale structure. Here we show how we can strongly constrain both AS2(k) and the cosmological parameters by combining the data from the Microwave Anisotropy Probe (MAP) and the galaxy redshift survey from the Sloan Digital Sky Survey (SDSS). We allow AS2(k) to be a free function, and thus probe features in the primordial power spectrum on all scales. MAP and SDSS have scale-dependent measurement errors that decrease in opposite directions on astrophysically interesting scales; they complement each other and allow the measurement of the primordial power spectrum independent of inflationary models, giving us valuable information on physics in the early Universe, and providing clues to the correct inflationary model.