分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We investigate cosmological dynamics of multiple tachyon fields with inverse square potentials.A phase-space analysis of the spatially flat FRW models shows that there exists power-law cosmological scaling solutions. We study the stability of the solutions and find that the potential-kinetic-scaling solution is a global attractor. However, in the presence of a barotropic fluid the solution is an attractor only in one region of the parameter space and the tracking solution is an attractor in the other region. We briefly discuss the physical consequences of these results.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We investigate the nucleosynthesis constraint on Lorentz invariance violation in the neutrino sector which influences the formation of light elements by altering the energy density of the Universe and weak reaction rates prior to and during the big-bang nucleosynthesis epoch. We derive the weak reaction rates in the Lorentz-violating extension of the standard model. Using measurements of the primordial helium-4 and deuterium abundances, we give a tighter constraint on the deformed parameter than that derived from measurements of the cosmic microwave background anisotropies.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We study asymptotically AdS topological black hole solutions with k = 0 (plane symmetric) in the Einstein gravity with Gauss-Bonnet term, the dilaton and a “cosmo-logical constant” in various dimensions. We derive the field equations for suitable ansatz for general D dimensions. We determine the parameter regions including dilaton cou-plings where such solutions exist and construct black hole solutions of various masses numerically in D = 4, 5, 6 and 10 dimensional spacetime with (D − 2)-dimensional hypersurface of zero curvature.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We develop a theoretical method of constructing the quintessence potential directly from the effective equation of state function w(z), which describes the properties of the dark energy. We apply our method to four parametrizations of equation of state parameter and discuss the general features of the resulting potentials. In particular, it is shown that the constructed quintessence potentials are all in the form of a runaway type.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We present a nonparametric approach to reconstruct the interaction between dark energy and dark matter directly from SNIa Union 2.1 data using Gaussian processes, which is a fully Bayesian approach for smoothing data. In this method, once the equation of state (w) of dark energy is specified, the interaction can be reconstructed as a function of redshift. For the decaying vacuum energy case with w = −1, the reconstructed interaction is consistent with the standard #3;CDM model, namely, there is no evidence for the interaction. This also holds for the constant w cases from −0.9 to −1.1 and for the Chevallier-Polarski-Linder (CPL) parametrization case. If the equation of state deviates obviously from −1, the reconstructed interaction exists at 95% confidence level. This shows the degeneracy between the interaction and the equation of state of dark energy when they get constraints from the observational data.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We demonstrate the attractor behavior of inflation driven by a scalar field or a tachyon field in the context of recently proposed four-dimensional effective gravity induced on the world-volume of a three-brane in five-dimensional Einstein gravity, and we obtain a set of exact inflationary solutions.Phase portraits indicate that an initial kinetic term decays rapidly and it does not prevent the onset of inflation. The trajectories more rapidly reach the slow rolling curve in braneworld scenario than in the standard cosmology.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We investigate the cosmological attractor of the minimally coupled, self-interacting phantom field with a positive energy density but negative pressure. It is proved that the phantom cosmology is rigid in the sense that there exists a unique attractor solution. We plot the trajectories in the phase space numerically for the phantom field with three typical potentials. Phase portraits indicate that an initial kinetic term decays rapidly and the trajectories reach the unique attractor curve. We find that the curve corresponds to the slow-climb solution.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: The newly released Planck CMB data place tight constraints on slow-roll inflationary models. Some of commonly discussed inflationary potentials are disfavored due mainly to the large tensor-to-scalar ratio. In this paper we show that these potentials may be in good agreement with the Planck data when the inflaton has a non-minimal coupling to the Gauss-Bonnet term. Moreover, such a coupling violates the consistency relation between the tensor spectral index and tensor-to-scalar ratio. If the tensor spectral index is allowed to vary freely, the Planck constraints on the tensor-to-scalar ratio are slightly improved.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: Measuring the deviation from scale invariance of the primordial power spectrum is a critical test of inflation. In this paper we reconstruct the shape of the primordial power spectrum of curvature perturbations from the cosmic microwave background data, including the 7-year Wilkinson Microwave Anisotropy Probe data and the Atacama Cosmology Tele-scope 148 GHz data, by using a binning method of a cubic spline interpolation in log-log space. We find that the power-law spectrum is preferred by the data and that the Harrison-Zel’dovich spectrum is disfavored at 95% confidence level. These conclusions hold with and without allowing for tensor modes, however the simpler model without tensors is preferred by the data. We do not find evidence for a feature in the primordial power spectrum – in full agreement with generic predictions from cosmological inflation.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic #12;elds can be generated during contraction without encounter-ing strong coupling and backreaction issues. The #12;elds may seed large-scale magnetic #12;elds with observationally interesting strengths. This result leads to a the oretical constraint on the relation of the energy scale of the bounce cosmology to the number of e#11;ective e-folding of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic #12;elds. We show that this constraint can be satis#12;ed in a sizable region of the parameter space for the nonsingular bounce cosmology.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-09-27
摘要: We derive the Boltzmann equation in the synchronous gauge for massive neutrinos with a deformed dispersion relation. Combining the 7-year WMAP data with lower-redshift measurements of the expansion rate, we give constraints on the deformation parameter and find that the deformation parameter is strong degenerate with the physical dark matter density rather than the neutrino mass. Our results show that there is no evidence for Lorentz invariant violation in the neutrino sector. The ongoing Planck experiment could provide improved constraints on the deformation parameter.