119163343
Primordial Gravitational Waves and Cosmic Microwave Background Radiation
This is a summary of presentations delivered at the OC1 parallel session "Primordial Gravitational Waves and the CMB" of the 12th Marcel Grossmann meeting in Paris, July 2009. The reports and discussions demonstrated significant progress that was achieved in theory and observations. It appears that the existing data provide some indications of the presence of gravitational wave contribution to the CMB anisotropies, while ongoing and planned observational efforts are likely to convert these indications into more confident statements about the actual detection.
15031895
Separate the Tensor Perturbation From the CMB Temperature Anisotropy Power Spectrum
For studying the difference effect on the Cosmic Microwave Background Radiation (CMB) anisotropy spectrum by scalar and tensor perturbation, we define another function Alm, which can reflect the effect of different magnetic quantum number m. For a given l, we find that the ratio relations of Alm is different for the scalar perturbation sources and tensor perturbation sources. This give a new way to directly separate the tensor perturbation from CMB anisotropy power spectrum. Applying this method to study the CMB anisotropy quadrupole observed by COBE, we find that this quadrupole is not generated by isotropy scalar perturbation, the contribute of tensor perturbation is obvious. We can also study the anisotropy of the scalar perturbation by measuring the values of Alm in different coordinate system. PACS numbers: 98.80.-k, 98.80.Es, 04.30.-w, 04.62+v, e-mail: wzhao7@mail.ustc.edu.cn The inflation models mainly predicted two kind of important perturbations: the scalar perturbation and the tensor perturbation (relic gravitational waves)[1]. The detection of them is the main way to research the inflation physics, especially the tensor perturbation, which directly relate to the energy scale of the inflation, and can give the clearer information about the evolution of the Universe[1, 2]. The detection of these two kind of perturbation are mainly by the researching of the CMB anisotropy and polarization. A lot of people have discussed the anisotropy and polarization power spectrum generated by scalar perturbation and tensor perturbation in numerical method or in analytic method[3]. In these years, the precise observation of the CMB anisotropy and polarization have made an important progress, especially the release of the high resolution full sky Wilkinson Microwave Anisotropy Probe (WMAP) data[4]. These results all fit very well with the prediction of inflation-ΛCDM cosmological model. We all know that the scalar perturbation can generate CMB temperature-temperature power spectrum (C l ), the electric-electric polarization power spectrum (C l ), and the cross-correlation power spectrum (C TE l ); but the tensor perturbation also can generate magnetic-magnetic polarization power spectrum (C l ).
170278
Yang–Mills condensate dark energy coupled with matter and radiation
The coincidence problem is studied for the dark energy model of effective Yang?Mills condensate (YMC) in a flat expanding universe during the matter-dominated stage. The YMC energy ?y(t) is taken to represent the dark energy, which is coupled either with the matter ?m(t), or with both the matter and the radiation components ?r(t). The effective YM Lagrangian is completely determined by the quantum field theory up to 1-loop order with an energy scale ~10?3 eV as a model parameter, and for each coupling, there is an extra model parameter. We have studied extensively the coupling models: the YMC decaying into the matter and the radiation; or vice versa the matter and radiation decaying into the YMC. It is found that, starting from the equality of radiation-matter ?mi = ?ri, for a wide range of initial conditions of ?yi = (10?10, 10?2)?mi, the models have a scaling solution during the early stages, and the YMC levels off and becomes dominant at late time, and the present state with ?y 0.7, ?m 0.3 and ?r 10?5 is always achieved. If the YMC decays into a component, then this component also levels off later and approaches a constant value asymptotically, and the equation of state (EoS) of the YMC wy = ?y/py crosses over ?1 and takes the value wy ?1.1 at z = 0. If the matter and radiation decay into the YMC, then ?m(t) ? a(t)?3 and ?r(t) ? a(t)?4 approximately for all the time, and wy approaches ?1 but does not cross over ?1. We have also demonstrated that, at t ? ?, the coupled dynamics for (?y(t), ?m(t), ?r(t)) is a stable attractor. Therefore, under generic circumstances, the existence of the scaling solution during the early stages and the subsequential exit from the scaling regime around z (0.3?0.5) are inevitable. Thus the coincidence problem can be naturally solved in the YMC dark energy models.
119114042
Hint of relic gravitational waves in the Planck and WMAP data
Relic gravitational waves (RGWs) leave well-understood imprints on the anisotropies in the temperature and polarization of cosmic microwave background (CMB) radiation. In the TT and TE information channels, which have been well observed by WMAP and Planck missions, RGWs compete with density perturbations mainly at low multipoles. It is dangerous to include high-multipole CMB data in the search for gravitational waves, as the spectral indices may not be constants. In this paper, we repeat our previous work [W.Zhao & L.P.Grishchuk, Phys.Rev.D {\bf 82}, 123008 (2010)] by utilizing the Planck TT and WMAP TE data in the low-multipole range $\ell\le100$. We find that our previous result is confirmed {with higher confidence}. The constraint on the tensor-to-scalar ratio from Planck TT and WMAP TE data is $r\in [0.06,~0.60]$ (68% C.L.) with the maximum likelihood at around $r\sim 0.2$. Correspondingly, the spectral index at the pivot wavenumber $k_*=0.002$Mpc$^{-1}$ is $n_s=1.13^{+0.07}_{-0.08}$, which is larger than 1 at more than $1\sigma$ level. So, we conclude that the new released CMB data indicate a stronger hint for the RGWs with the amplitude $r\sim 0.2$, which is hopeful to be confirmed by the imminent BICEP and Planck polarization data.
102301777
Constraints on standard and non-standard early Universe models from CMB B-mode polarization
We investigate the observational signatures of three models of the early Universe in the B-mode polarization of the Cosmic Microwave Background (CMB) radiation. In addition to the standard single field inflationary model, we also consider the constraints obtainable on the loop quantum cosmology model (from Loop Quantum Gravity) and on cosmic strings, expected to be copiously produced during the latter stages of Brane inflation. We first examine the observational features of the three models, and then use current B-mode polarization data from the BICEP and QUaD experiments to constrain their parameters. We also examine the detectability of the primordial B-mode signal predicted by these models and forecast the parameter constraints achievable with future CMB polarization experiments. We find that: (a) since B-mode polarization measurements are mostly unaffected by parameter degeneracies, they provide the cleanest probe of these early Universe models; (b) using the BICEP and QUaD data we obtain the following parameter constraints: r = 0.02+0.31−0.26 (1σ for the tensor-to-scalar ratio in the single field inflationary model); m < 1.36 × 10−8Mpl and k* < 2.43 × 10−4 Mpc−1 (1σ for the mass and scale parameters in the loop quantum cosmology model); and Gμ < 5.77 × 10−7 (1σ for the cosmic string tension); (c) future CMB observations (both satellite missions and forthcoming sub-orbital experiments) will provide much more rigorous tests of these early Universe models.
119522211
Quintessence models with an oscillating equation of state and their potentials
In this paper, we investigate the quintessence models with an oscillating equation of state (EoS) and their potentials. From the constructed potentials, which have the EoS of $\omega_{\phi}=\omega_0+\omega_1\sin z$, we find they are all the oscillating functions of the field $\phi$, and the oscillating amplitudes are decreasing (or increasing) with $\phi$. From the evolutive equation of the field $\phi$, we find this is caused by the expansion of the universe. This also makes that it is very difficult to build a model whose EoS oscillates forever. However one can build a model with EoS oscillating for a period. Then we discuss three quintessence models, which are the combinations of the invert power law functions and the oscillating functions of the field $\phi$. We find they all follow the oscillating EoS.
60918622
Modelling and Building Graphics Systems: GKS
The GKS-2D standard specifications were expressed by a combination of the Entity-Relationship (ER) model with Dataflow and State Transition diagrams. Our description was not only precise and complete, but also easier to understand than the original standard, mainly because of the use of diagrams. Starting from this description a GKS system was rapidly constructed making use of a general purpose subroutine package for ER data definition and manipulation. The performance of this GKS was found to be similar to that of commercially available products. Our description was extended to GKS-3D and is generally applicable to any graphics system. We suggest that such an approach would lead to more rapid convergence in the design of graphics standards and the construction of the corresponding systems.
31529006
Screening length, dispersion relations and quark potential in thermo field dynamics
The screening length in a quark-gluon plasma, the dispersion relations of thermal gluon self-energy and the quark potential at high temperature are studied within the thermo field dynamics framework. By calculating the real and imaginary parts, of the gluon self-energy in one-loop order in thermo field dynamics, we obtain an expression for the screening length in a quark-gluon plasma and the dispersion relation between the real and imaginary parts. At high temperature, using photon exchange between electron-positron in a skeleton expansion and ladder approximation, the screened Coulomb potential and an expression for the screened quark potential is obtained.