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Observation Constraints on the Simplified GCG Model

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Chinese Physics Letters 2007年第6期24卷 1782-1785页

作者：董素梅吴普训 School of Sciences and Institute of Math-Physics Central South University of Forestry and Technology Changsha 410004

A simplified version of generalized Chaplygin gas （GCG） as a dark energy model is studied. By using the latest 162 ESSENCE type Ia supernovae （She Ia） data, 30 high redshift She Ia data, the baryonic acoustic oscillation peak from SDSS and the CMB data from WMAP3, a strong constraint on this simplified GCG model is obtained. At the 95.4% confidence level we obtain 0.21 ≤ Ωm ≤ 0.31 and 0.994 〈 α 〈 1.0 with the best fit Ωm = 0.25 and a = 1. This best fit scenario corresponds to an accelerating universe with qo ≈-0.65 and z ≈ 0.81 （a redshiR of cosmic phase transition from deceleration to acceleration）.

关键词： GENERALIZED CHAPLYGIN-GAS EQUATION-OF-STATE SNE-IA DATA DARK-ENERGY COSMOLOGICAL CONSTANT SUPERNOVA DATA BAYESIAN-ANALYSIS MATTER UNIFICATION STATISTICS

Observational Constraints on the Unified Dark-Energy-Dark-Matter Model

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Chinese Physics Letters 2007年第3期24卷 843-845页

作者：吴普训余洪伟 School of Sciences and Institute of Physics Central South University of Forestry and Technology Changsha 410004 Department of Physics and Institute of Physics Normal University Changsha 410081

We investigate the constraints on a generalized Chaplygin gas （GCG） model using the gold sample type-Ia supernovae （She Ia） data, the new Supernova Legacy Survey （SNLS） Sne Ia data and the size of baryonic acoustic oscillation peak found in Sloan Digital Sky Survey （SDSS）. In a spatially flat universe case we obtain, at a 95.4% confidence level, A8 = 0.76^＋0.07 -0.07 and α= 0.028^＋0.322 -0.2382 Our results are consistent with the ACDM model （α= 0）, but rule out the standard Chaplygin gas model （α= 1）.

关键词： GENERALIZED CHAPLYGIN-GAS HIGH-REDSHIFT SUPERNOVAE HUBBLE-SPACE-TELESCOPE COSMOLOGICAL PARAMETERS CONSTANT OMEGA(LAMBDA) STATISTICS MAXIMA-1 OMEGA(M) UNIVERSE

Vacuum Polarization of Twisted Scalars in a Non—simply Connected Space—time and Its Effects

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Chinese Physics Letters 2002年第11期19卷 1589-1591页

作者：吴普训余洪伟 DepartmentofPhysicsandInstituteofPhysics HunanNormalUniversityChangsha410081

The vacuum polarization due to twisted scalar fields is investigated in a non-simply connected space-time. It is found that some photon modes acquire an imaginary topological mass, thus travelling at a superluminal speed. Topological bi-refringence is expected for photons propagating perpendicularly to the compactification direction. The effect of a topological photon mass on the static properties of electromagnetic fields is also considered for the cases of both twisted and untwisted scalar fields. Our result shows that in the untwisted case the magnetic field is screened along the radial direction for massive photon modes, while in the twisted case no screening occurs and the magnetic fields merely oscillate.

关键词： Photons

Relic Gravitational Waves and Trans-Planckian Physics

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Chinese Physics Letters 2005年第9期22卷 2161-2164页

作者：吴普训余洪伟 Department of Physics and Institute of Physics Hunan Normal University Changsha 410081

Assuming that the effects of trans-Planckian physics are encoded in the choice of initial conditions, mode by mode, for vacuum states at the time when its wavelength becomes equal to the scale of new physics （Planck＇s scale for example）, we calculate the spectrum of energy densities of total relic gravitational waves from de Sitter inflation to the matter dominated universe. Our results show that the spectrum acquires corrections due to the consideration of trans-Planckian physics and these corrections depend sensitively on the vacuum state that was actually realized at the beginning of the inflation.

关键词： CHARGED TEST PARTICLE VACUUM FLUCTUATIONS INFLATION SPECTRUM UNIVERSE MOTION SCALE

Test of the Cosmic Transparency with the Baryon Acoustic Oscillation and Type Ia Supernova Data

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Chinese Physics Letters 2016年第5期33卷 149-151页

作者：李合昆吴普训余洪伟 Center of Nonlinear Science and Department of Physics Ningbo University

We use the latest baryon acoustic oscillation and Union 2.1 type Ia supernova data to test the cosmic opacity between different redshift regions without assuming any cosmological models. It is found that the universe may be opaque between the redshift regions 0.35 0.44, 0.44 0.57 and 0.6-0.73 since the best fit values of cosmic opacity in these regions are positive, while a transparent universe is favored in the redshift region 0.57-0.63. However, in general, a transparent universe is still consistent with observations at the lo confidence level.

关键词： of in Test of the Cosmic Transparency with the Baryon Acoustic Oscillation and Type Ia Supernova Data with that is

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Growth of linear matter perturbations and current observational constraints

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Chinese Physics B 2010年第7期19卷 624-629页

作者：付响云吴普训余洪伟 Department of Physics and Institute of Physics Hunan Normal University

We discuss, using a recently proposed parametrization for the growth index of linear matter perturbations, the observational constraints on the wCDM model and the Dvali Gabadadze-Porrati （DGP） model with all current growth factor data. We find that the wCDM model is allowed by the observations at the 1σ confidence level, while the DCP model is only consistent with observations at 2σ confidence level.

关键词： dark energy DGP model matter perturbations

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Constraining the Generalized and Superfluid Chaplygin Gas Models with the Sandage-Loeb Test

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Chinese Physics Letters 2015年第5期32卷 174-177页

作者：朱文涛吴普训余洪伟 Center of Nonlinear Science and Department of Physics Ningbo University

The Sandage Loeb （SL） test is a direct measurement of the cosmic expansion by probing the redshift drifts of quasi-stellar objects in the ＇redshift desert＇ of 2 〈 z 〈 5. In this work, we investigate its constraints on the unified dark energy and dark matter models including the generalized Chaplygin gas and the superfluid Chaplygin gas. In addition, type Ia supernovae （SNIa） data and the distance ratios derived from the cosmic microwave background radiation and baryon acoustic oscillation observations （CMB/BAO） are also used. We find that the mock SL data gives the tightest constraints on the model parameters and it can help to reduce the parameter regions allowed by the present SNIa＋CMB/BAO by about 75% when all datasets considered are combined. Thus the SL test is a worthy and long awaited measurement to probe effectively the cosmic expanding history and the properties of dark energy.

关键词： CMB BA Constraining the Generalized and Superfluid Chaplygin Gas Models with the Sandage-Loeb Test

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Inflationary dynamics in the braneworld scenarios

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Chinese Physics B 2013年第5期22卷 669-673页

作者：张开源吴普训余洪伟 Center of Nonlinear Science and Department of Physics Ningbo University

We analyze the attractor behaviour of the inflation field in braneworld scenarios using the Hamilton-Jacobi formalism, where the Friedmann equation has the form of H2 = ρ + ε(2ρ0ρ)1/2or H2 = ρ + ερ2/2σ , with ε = ±1. We find that in all models the linear homogeneous perturbation can decay exponentially as the scalar field rolls down its potential. However, in the case of a -ρ2 correction to the standard cosmology with ρ 1. Our results show that the perturbation decays more quickly in models with positive-energy correction than in the standard cosmology, which is opposite to the case of negative-energy correction. Thus, the positive-energy modification rather than the negative one can assist the inflation and widen the range of initial conditions.

关键词： inflation braneworld attractor

Quantum Inequality for Negative Energy Density States of Massive Dirac Field in Four-Dimensional Spacetime

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Chinese Physics Letters 2003年第12期20卷 2105-2106页

作者：舒维星吴普训余洪伟 DepartmentofPhysicsandInstituteofPhysics HunanNormalUniversityChangsha410081

Negative energy density and the quantum inequality are examined for the Dirac field. A proof is given of the quantum inequality for negative energy densities in the massive Dirac field produced by the superposition of... 详细信息

关键词： Quantum Inequality Negative Energy Density States Massive Dirac Field Four-Dimensional Spacetime