اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدNew Limits on Coupled Dark Energy from Planck
300
0
0.0
(
0
)
تأليف
Jun-Qing Xia
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Recently, the Planck collaboration has released the first cosmological papers providing the high resolution, full sky, maps of the cosmic microwave background (CMB) temperature anisotropies. It is crucial to understand that whether the accelerating expansion of our universe at present is driven by an unknown energy component (Dark Energy) or a modification to general relativity (Modified Gravity). In this paper we study the coupled dark energy models, in which the quintessence scalar field nontrivially couples to the cold dark matter, with the strength parameter of interaction $beta$. Using the Planck data alone, we obtain that the strength of interaction between dark sectors is constrained as $beta < 0.102$ at $95%$ confidence level, which is tighter than that from the WMAP9 data alone. Combining the Planck data with other probes, like the Baryon Acoustic Oscillation (BAO), Type-Ia supernovae ``Union2.1 compilation and the CMB lensing data from Planck measurement, we find the tight constraint on the strength of interaction $beta < 0.052$ ($95%$ C.L.). Interestingly, we also find a non-zero coupling $beta = 0.078 pm 0.022$ ($68%$ C.L.) when we use the Planck, the ``SNLS supernovae samples, and the prior on the Hubble constant from the Hubble Space Telescope (HST) together. This evidence for the coupled dark energy models mainly comes from a tension between constraints on the Hubble constant from the Planck measurement and the local direct $H_0$ probes from HST.
قيم البحث
اقرأ أيضاً
We present new constraints on coupled dark energy from the recent measurements of the Cosmic Microwave Background Anisotropies from the Planck satellite mission. We found that a coupled dark energy model is fully compatible with the Planck measuremen
ts, deriving a weak bound on the dark matter-dark energy coupling parameter xi=-0.49^{+0.19}_{-0.31} at 68% c.l.. Moreover if Planck data are fitted to a coupled dark energy scenario, the constraint on the Hubble constant is relaxed to H_0=72.1^{+3.2}_{-2.3} km/s/Mpc, solving the tension with the Hubble Space Telescope value. We show that a combined Planck+HST analysis provides significant evidence for coupled dark energy finding a non-zero value for the coupling parameter xi, with -0.90< xi <-0.22 at 95% c.l.. We also consider the combined constraints from the Planck data plus the BAO measurements of the 6dF Galaxy Survey, the Sloan Digital Sky Survey and the Baron Oscillation Spectroscopic Survey.
We determine constraints on spatially-flat tilted dynamical dark energy XCDM and $phi$CDM inflation models by analyzing Planck 2015 cosmic microwave background (CMB) anisotropy data and baryon acoustic oscillation (BAO) distance measurements. XCDM is
a simple and widely used but physically inconsistent parameterization of dynamical dark energy, while the $phi$CDM model is a physically consistent one in which a scalar field $phi$ with an inverse power-law potential energy density powers the currently accelerating cosmological expansion. Both these models have one additional parameter compared to standard $Lambda$CDM and both better fit the TT + lowP + lensing + BAO data than does the standard tilted flat-$Lambda$CDM model, with $Delta chi^2 = -1.26 (-1.60)$ for the XCDM ($phi$CDM) model relative to the $Lambda$CDM model. While this is a 1.1$sigma$ (1.3$sigma$) improvement over standard $Lambda$CDM and so not significant, dynamical dark energy models cannot be ruled out. In addition, both dynamical dark energy models reduce the tension between the Planck 2015 CMB anisotropy and the weak lensing $sigma_8$ constraints.
Cosmic magnetic fields are observed to be coherent on large scales and could have a primordial origin. Non-Gaussian signals in the cosmic microwave background (CMB) are generated by primordial magnetic fields as the magnetic stresses and temperature
anisotropy they induce depend quadratically on the magnetic field. We compute the CMB scalar trispectrum on large angular scales, for nearly scale-invariant magnetic fields, sourced via the Sachs-Wolfe effect. The trispectra induced by magnetic energy density and by magnetic scalar anisotropic stress are found to have typical magnitudes of approximately $10^{-29}$ and $10^{-19}$, respectively. The scalar anisotropic stress trispectrum is also calculated in the flat-sky approximation and yields a similar result. Observational limits on CMB non-Gaussianity from the Planck mission data allow us to set upper limits of $B_0 lesssim 0.6 $ nG on the present value of the primordial cosmic magnetic field. Considering the inflationary magnetic curvature mode in the trispectrum can further tighten the magnetic field upper limit to $B_0 lesssim 0.05 $ nG. These sub-nanoGauss constraints from the magnetic trispectrum are the most stringent limits so far on the strength of primordial magnetic fields, on megaparsec scales, significantly better than the limits obtained from the CMB bispectrum and the CMB power spectrum.
We present new constraints on the relativistic neutrino effective number N_eff and on the Cosmic Microwave Background power spectrum lensing amplitude A_L from the recent Planck 2013 data release. Including observations of the CMB large angular scale
polarization from the WMAP satellite, we obtain the bounds N_eff = 3.71 +/- 0.40 and A_L = 1.25 +/- 0.13 at 68% c.l.. The Planck dataset alone is therefore suggesting the presence of a dark radiation component at 91.1% c.l. and hinting for a higher power spectrum lensing amplitude at 94.3% c.l.. We discuss the agreement of these results with the previous constraints obtained from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT). Considering the constraints on the cosmological parameters, we found a very good agreement with the previous WMAP+SPT analysis but a tension with the WMAP+ACT results, with the only exception of the lensing amplitude.
We study a phenomenological dark energy model which is rooted in the Veneziano ghost of QCD. In this dark energy model, the energy density of dark energy is proportional to Hubble parameter and the proportional coefficient is of the order $Lambda^3_{
QCD}$, where $Lambda_{QCD}$ is the mass scale of QCD. The universe has a de Sitter phase at late time and begins to accelerate at redshift around $z_{acc}sim0.6$. We also fit this model and give the constraints on model parameters, with current observational data including SnIa, BAO, CMB, BBN and Hubble parameter data. We find that the squared sound speed of the dark energy is negative, which may cause an instability. We also study the cosmological evolution of the dark energy with interaction with cold dark matter.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
