15948392
CMB Temperature Anisotropy Quadrupole Generated by Tensor Perturbation
Using the method suggested in Ref.\cite{zhao} and the Cosmic Microwave Background Radiation (CMB) temperature anisotropy quadrupole observed by COBE, we find that $C_2^T/C_2^S=5.9\pm2.7$, where $C_2^T$ and $C_2^S$ are the CMB anisotropy quadrupole generated by tensor perturbation and scalar perturbation respectively. But if using the $C_2^S$ predicted by the standard inflation-$\Lambda$CDM models, we can find that $C_2^T/C_2^S=0.11\pm0.04$. This result consists with prediction of inflation models, it also consists with the upper limit of the tensor perturbation which got from Ref.\cite{tensor}. From this result, we find the contribution on the CMB anisotropy is not too small to be omitted. So it is necessary to reestimate the cosmological parameters after considering the effect of the tensor perturbation. This result also suggests that the much damping of the CMB anisotropy quadrupole may be only occurring on the contribution of scalar perturbation, but not on the tensor perturbation, this is a new character of this damping, and will be a very constraint on the explanation of it.
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.
118702519
Fluctuations of cosmological birefringence and the effect on CMB B-mode polarization
The cosmological birefringence caused by the coupling between the cosmic scalar field and the cosmic microwave background (CMB) photons through the Chern-Simons term can rotate the polarization planes of the photons, and mix the CMB E-mode and B-mode polarizations. The rotation angle induced by the dynamical scalar field can be separated into the isotropic background part and the anisotropic fluctuations. The effect of the background part has been be studied in the previous work (Zhao & Li, arXiv:1402.4324). In this paper, we focus on the influence of the anisotropies of the rotation angle. We first assume that the cosmic scalar field is massless, consistent with other works, we find that the rotation spectrum can be quite large, which may be detected by the potential CMB observations. However, if the scalar field is identified as the quintessence field, by detailed discussing both the entropy and adiabatic perturbation modes for the first time, we find that the anisotropies of the rotation angle are always too small to be detectable.In addition, as the main goal of this paper, we investigate the effect of rotated polarization power spectrum on the detection of relic gravitational waves. we find that, the rotated B-mode polarization could be fairly large, and comparable with those generated by the gravitational waves. This forms a new contamination for the detection of relic gravitational waves in the CMB. In particular, we also propose the method to reconstruct and subtract the rotated B-mode polarization, by which the residuals become negligible for the gravitational-wave detection.
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.
10626654
Improved calculation of relic gravitational waves
In this paper, we have improved the calculation of the relic gravitational waves (RGW) in two aspects. First, we investigate the transfer function by taking into consideration the redshift-suppression effect, the accelerating expansion effect, the damping effect of free-streaming relativistic particles, and the damping effect of cosmic phase transition, and give a simple approximate analytic expression, which clearly illustrates the dependence on the cosmological parameters. Second, we develop a numerical method to calculate the primordial power spectrum of RGW in a very wide frequency range, where the observed constraints on ns (the scalar spectral index) and PS(k0) (the amplitude of primordial scalar spectrum) and the Hamilton–Jacobi equation are used. This method is applied to two kinds of inflationary models, which satisfy the current constraints on ns, α (the running of ns) and r (the tensor–scalar ratio). We plot them in the r − Ωg diagram, where Ωg is the strength of RGW, and study their measurements from the cosmic microwave background (CMB) experiments and laser interferometers.
55090406
Constraints of relic gravitational waves by pulsar timing arrays: Forecasts for the FAST and SKA projects
Measurement of the pulsar timing residuals provides a direct way to detect relic gravitational waves at the frequency $f\sim 1/{\rm yr}$. In this paper, we investigate the constraints on the inflationary parameters, the tensor-to-scalar ratio $r$ and the tensor spectral index $n_t$, by the current and future Pulsar Timing Arrays (PTAs). We find that Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China and the planned Square Kilometer Array (SKA) projects have the fairly strong abilities to test the phantom-like inflationary models. If $r=0.1$, FAST could give the constraint on the spectral index $n_t<0.56$, and SKA gives $n_t<0.32$. While an observation with the total time T=20 yr, the pulsar noise level $\sigma_w=30$ns and the monitored pulsar number $n=200$, could even constrain $n_t<0.07$. These are much tighter than those inferred from the current results of Parkers Pulsar Timing Array (PPTA), European Pulsar Timing Array (EPTA) and North American Nanohertz Observatory for Gravitational waves (NANOGrav). Especially, by studying the effects of various observational factors on the sensitivities of PTAs, we found that compared with $\sigma_w$ and $n$, the total observation time $T$ has the most significant effect.
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.
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.