118584779
Reconstruction of the primordial power spectra with Planck and BICEP2 data
By using the cubic spline interpolation method, we reconstruct the shape of the primordial scalar and tensor power spectra from the recently released Planck temperature and BICEP2 polarization cosmic microwave background data. We find that the vanishing scalar index running (dn(s)= d ln k) model is strongly disfavored at more than 3 sigma confidence level on the k = 0.0002 Mpc(-1) scale. Furthermore, the power-law parametrization gives a blue-tilt tensor spectrum, no matter using only the first five bandpowers n(t) = 1.20(-0.64)(+0.56) (95% C.L.) or the full nine bandpowers nt 1.24(-0.58)(+0.51) (95% C.L.) of BICEP2 data sets. Unlike the large tensor-to-scalar ratio value (r similar to 0.20) under the scale-invariant tensor spectrum assumption, our interpolation approach gives r(0.002) < 0.060 (95% C.L.) by using the first five bandpowers of BICEP2 data. After comparing the results with/without BICEP2 data, we find that Planck temperature with small tensor amplitude signals and BICEP2 polarization data with large tensor amplitude signals dominate the tensor spectrum reconstruction on the large and small scales, respectively. Hence, the resulting blue tensor tilt actually reflects the tension between Planck and BICEP2 data.
15707844
Holography, UV/IR Relation, Causal Entropy Bound, and Dark Energy
The constraint on the total energy in a given spatial region is given from holography by the mass of a black hole that just fits in that region, which leads to an UV/IR relation: the maximal energy density in that region is propotional to M(p)(2)/L(2), wher M(p) is the Planck mass and L is the spatial scale of that region under consideration. Assuming that maximal black hole in the universe is formed through gravitational collapse of perturbations in the universe, then the "Jeans" scale of the perturbations gives a causal connection scale R(CC). For gravitational perturbations, R(CC)(-2) = Max ((H) over dot + 2H(2), -(H) over dot) for a flat universe. We study the cosmological dynamics of the corresponding vacuum energy density by choosing the causal connection scale as the IR cutoff in the UV/IR relation, in the cases of the vacuum energy density as an independently conserved energy component and an effective dynamical cosmological constant, respectively. It turns out that only the case with the choice R(CC)(-2) = (H) over dot + 2H(2), could be consistent with the current cosmological observations when the vacuum density appears as an independently conserved energy component. In this case, the model is called holographic Ricci scalar dark energy model in the literature.
118528998
Note on self-gravitating radiation in AdS spacetime
Recently Vaganov and Hammersley investigated independently the equilibrium self-gravitating radiation in higher (d >= 4)-dimensional, spherically symmetric anti-de Sitter space. It was found that in 4 = 11, the temperature, mass, and entropy of the self-gravitating configuration are monotonic functions of the central energy density, asymptoting to their maxima as the central density goes to infinity. In this paper we investigate the equilibrium self-gravitating radiation in higher-dimensional, plane-symmetric anti-de Sitter space. We find that there exist essential differences from the spherically syrnmetric case: In each dimension (d >= 4), there are maximal mass (density), maximal entropy (density), and maximal temperature configurations; they do not appear at the same central energy density; the oscillation behavior appearing in the spherically symmetric case does not happen in this case; and the mass (density), as a function of the central energy density, increases first and reaches its maximum at a certain central energy density and then decreases monotonically in 4 = 8, besides the maximum, the mass (density) of the equilibrium configuration has a minimum: the mass (density) first increases and reaches its maximum, then decreases to its minimum, and then increases to its asymptotic value monotonically. The reason causing the difference is discussed.
119185851
Timelike vector field dynamics in the early universe
We study the dynamics of a timelike vector field when the background spacetime is in an accelerating phase in the early universe. With a timelike vector field, an inflationary phase is shown to be difficult to realize, so we investigate the evolution of a vector field within a scalar field-driven inflation model. Also, we calculate the power spectrum of the vector field without considering the metric perturbations. While the time component of the vector field perturbations provides a scale invariant spectrum when ζ = 0, where ζ is a nonminimal coupling parameter, both the longitudinal and the transverse perturbations give a scale invariant spectrum when ζ = 1/6 in the absence of the coupling terms. The deviation of the power spectrum due to the coupling terms is calculated by use of the Greens’ function.
119229799
Cosmological parameter estimation from CMB and X-ray cluster after Planck
. We investigate constraints on cosmological parameters in three 8-parameter models with the summed neutrino mass as a free parameter, by a joint analysis of CCCP X-ray cluster data, the newly released Planck CMB data as well as some external data sets including baryon acoustic oscillation measurements from the 6dFGS, SDSS DR7 and BOSS DR9 surveys, and Hubble Space Telescope Ho measurement. We find that the combined data strongly favor a non-zero neutrino masses at more than 3 sigma confidence level in these non-vanilla models. Allowing the CMB lensing amplitude A(L) to vary, we find A(L) > 1 at 3 sigma confidence level. For dark energy with a constant equation of state w, we obtain w < -1 at 3 sigma confidence level. The estimate of the matter power spectrum amplitude 08 is discrepant with the Planck value at 2 sigma confidence level, which reflects some tension between X-ray cluster data and Planck data in these non-vanilla models. The tension can be alleviated by adding a 9% systematic shift in the cluster mass function.
119260706
Parametrized modified gravity constraints after Planck
We constrain $f(R)$ and chameleon-type modified gravity in the framework of the Berstchinger-Zukin parametrization using the recent released Planck data, including both CMB temperature power spectrum and lensing potential power spectrum. Some other external data sets are included, such as BAO measurements from the 6dFGS, SDSS DR7 and BOSS DR9 surveys, HST $H_0$ measurement and supernovae from Union2.1 compilation. We also use WMAP9yr data for consistency check and comparison. For $f(R)$ gravity, WMAP9yr results can only give quite a loose constraint on the modified gravity parameter $B_0$, which is related to the present value of the Compton wavelength of the extra scalar degree of freedom, $B_0<3.37$ at $95\% {\rm C.L.}$ We demonstrate that this constraint mainly comes from the late ISW effect. With only Planck CMB temperature power-spectrum data, we can improve the WMAP9yr result by a factor $3.7$ ($B_0<0.91$ at $95\% {\rm C.L.}$). If the Planck lensing potential power-spectrum data are also taken into account, the constraint can be further strenghtened by a factor $5.1$ ($B_0<0.18$ at $95\% {\rm C.L.}$). This major improvement mainly comes from the small-scale lensing signal. Furthermore, BAO, HST and supernovae data could slightly improve the $B_0$ bound ($B_0<0.12$ at $95\% {\rm C.L.}$).For the chameleon-type model, we find that the data set which we used cannot constrain the Compton wavelength $B_0$ and the potential index $s$ of chameleon field, but can give a tight constraint on the parameter $\beta_1=1.043^{+0.163}_{-0.104}$ at $95\% {\rm C.L.}$ ($\beta_1=1$ in general relativity), which accounts for the non-minimal coupling between the chameleon field and the matter component. In addition, we find that both modified gravity models we considered favor a relatively higher Hubble parameter than the concordance LCDM model in general relativity.
16198413
Decoherence of Correlation Histories
AbstractWe use a λΦ 4 scalar quantum ﬁeld theory to illustrate a new approach tothe study of quantum to classical transition. In this approach, the decoherencefunctional is employed to assign probabilities to consistent histories deﬁned interms of correlations among the ﬁelds at separate points, rather than the ﬁelditself. We present expressions for the quantum amplitudes associated with suchhistories, as well as for the decoherence functional between two of them. Thedynamics of an individual consistent history may be described by a Langevin-type equation, which we derive. Dedicated to Professor Brill on the occasion of his sixtieth birthday, August 1993 1. Introduction1.1. Interpretations of Quantum Mechanics and Paradigmsof Statistical Mechanics This paper attempts to bring together two basic concepts, one from the foundationsof statistical mechanics and the other from the foundations of quantum mechanics,for the purpose of addressing two basic issues in physics:1) the quantum to classical transition, and2) the quantum origin of stochastic dynamics.Both issues draw in the interlaced eﬀects of dissipation, decoherence, noise, and ﬂuc-tuation. A central concern is the role played by coarse-graining –the naturalness of itschoice, the eﬀectiveness of its implementation and the relevance of its consequences.On the fundations of quantum mechanics, a number of alternative interpretationsexists, e.g., the Copenhagen interpretation, the many-world interpretation [1], theconsistent history interpretations [2], to name just a few (see [3] for a recent review).
119337153
Correlation dynamics of quantum fields and black hole information paradox
In recent years a statistical mechanics description of particles, fields and spacetime based on the concept of quantum open systems and the influence functional formalism has been introduced. It reproduces in full the established theory of quantum fields in curved spacetime and contains also a microscopic description of their statistical properties, such as noise, fluctuations, decoherence, and dissipation. This new framework allows one to explore the quantum statistical properties of spacetime at the interface between the semiclassical and quantum gravity regimes, as well as important non-equilibrium processes in the early universe and black holes, such as particle creation, entropy generation, galaxy formation, Hawking radiation, gravitational collapse, backreaction and the black hole end-state and information lost issues. Here we give a summary of the theory of correlation dynamics of quantum fields and describe how this conceptual scheme coupled with scaling behavior near the infrared limit can shed light on the black hole information paradox.
45195
Radiation Reaction in Schwarzschild Spacetime: Retarded Green's Function via Hadamard-WKB Expansion
An analytic method is given for deriving the part of the retarded Green’s function v(x, x) that contributes to the tail term in the radiation reaction force felt by a particle coupled to a massless minimally coupled scalar field. The method gives an expansion of v(x, x) for small separations of the points x, x valid for an arbitrary static spherically symmetric spacetime. It is obtained by using a WKB approximation for the Euclidean Green’s function for the massless minimally coupled scalar field and is equivalent to the DeWittSchwinger expansion for v(x, x). The first few terms in this expansion are displayed here for the case of Schwarzschild spacetime.
121042937
Anisotropy damping through quantum effects in the early universe
We consider a quantized field in a Bianchi type-I anisotropically expanding universe. A suitable expectation value of the renormalized energy-momentum tensor acts as the source of the metric in the Einstein equations. The coupled set of differential equations is numerically integrated, with the help of several approximations, in the case when the quantized field is the massless conformal scalar field. Boundary conditions are imposed at an initial time t/sub 0/ of the order of the Planck time, with the initial expansion rates varying over a wide range consistent with the constraints. It is found that the expansion rates tend toward isotropy and approach a radiation-filled Friedman expansion in an interval of less than 10/sup 3/ Planck times, for the full range of initial expansion rates considered.
121749669
Quantum dissipative processes and gravitational entropy of the universe
Abstract We discuss the meaning of gravitational entropy of the universe when quantum dissipative processes like cosmological particle production are important and propose to use the entropy generated in these processes as a measure of the change in gravitational entropy of the spacetime dynamics. Penrose's Weyl Curvature Hypothesis is re-examined in this generalized context. It is shown that gravitational entropy defined as such can actually decrease in the quantum regime by the action of vacuum viscosity. The theoretical and cosmological implications of this postulate is discussed.