118396565
Models of the Primordial Standard Clock
Oscillating massive fields in the primordial universe can be used as Standard Clocks. The ticks of these oscillations induce features in the density perturbations, which directly record the time evolution of the scale factor of the primordial universe, thus if detected, provide a direct evidence for the inflation scenario or the alternatives. In this paper, we construct a full inflationary model of primordial Standard Clock and study its predictions on the density perturbations. This model provides a full realization of several key features proposed previously. We compare the theoretical predictions from inflation and alternative scenarios with the Planck 2013 temperature data on Cosmic Microwave Background (CMB), and identify a statistically marginal but interesting candidate. We discuss how future CMB temperature and polarization data, non-Gaussianity analysis and Large Scale Structure data may be used to further test or constrain the Standard Clock signals.
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.
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.
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.
117823676
Thermodynamics for Kodama observer in general spherically symmetric spacetimes
By following the spirit of arXiv:1003.5665, we define a new Tolman temperature of Kodama observer directly related to its acceleration. We give a generalized integral form of thermodynamics relation on virtual sphere of constant $r$ in non-static spherical symmetric spacetimes. This relation contains work term contributed by `redshift work density', `pressure density' and `gravitational work density'. We illustrate it in RN black hole, Dilaton-Maxwell-Einstein black hole and Vaidya black hole. We argue that the co-moving observers are not physically related to Kodama observers in FRW universe unless in the vacuum case. We also find that a generalized differential form of first law is difficult to be well defined, and it would not give more information than the integral form.
54499639
Hadron calorimetry in the L3 detector
Abstract The characteristics of the L3 hadron calorimeter as realized in the observation of hadronic jets and other events from e + e − collisions at LEP are presented and discussed. The pattern-recognition algorithm utilizing the fine granulatiry of the calorimeter is described, and the observed overall resolution of 10.2% for hadron jets from Z decay is reported. The use of the calorimeter in providing information on muon energy losses is also noted.
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.
56436935
Current observational constraints on cosmic doomsday
In a broad class of dark energy models, the universe may collapse within a finite time tc. Here we study a representative model of dark energy with a linear potential, V () = V0(1+α). This model is the simplest doomsday model, in which the universe collapses rather quickly after it stops expanding. Observational data from type Ia supernovae (SNe Ia), cosmic microwave background anisotropy (CMB), and large scale structure (LSS) are complementary in constraining dark energy models. Using the new SN Ia data (the Riess sample), the CMB data from WMAP, and the LSS data from 2dF, we find that the collapse time of the universe is (24) Gyr from today at 68% (95%) confidence.
119152267
Nontrivial geometries: Bounds on the curvature of the universe
Abstract Probing the geometry of the universe is one of the most important endevours in cosmology. Current observational data from the cosmic microwave background anisotropy (CMB), galaxy surveys and type Ia supernovae (SNe Ia) strongly constrain the curvature of the universe to be close to zero for a universe dominated by a cosmological constant or dark energy with a constant equation of state. Here we investigate the role of cosmic priors on deriving these tight bounds on geometry, by considering a landscape motivated scenario with an oscillating curvature term. We perform a likelihood analysis of current data under such a model of non-trivial geometry and find that the uncertainties on curvature, and correspondingly on parameters of the matter and dark energy sectors, are larger. Future dark energy experiments together with CMB data from experiments like Planck could dramatically improve our ability to constrain cosmic curvature under such models enabling us to probe possible imprints of quantum gravity.