Unified Dark Fluid with Constant Adiabatic Sound Speed: Including Entropic Perturbations

In this paper, we continue to study a unified dark fluid model with a constant adiabatic sound speed but with the entropic perturbations. When the entropic perturbations are included, an effective sound speed, which reduces to the adiabatic sound speed when the entropic perturbations are zero, has to be specified as an additional free model parameter. Due to the relations between the adiabatic sound speed and equations of state (EoS) $c^2_{s,ad}(a)=w(a)-d\ln(1+w(a))/3 d\ln a$, the equation of state can be determined up to an integration constant in principle when an adiabatic sound speed is given. Then there are two degrees of freedom to describe the linear perturbations for a fluid. Its micro-scale properties are characterized by its EoS or adiabatic sound speed and an effective sound speed. We take the effective sound speed and adiabatic sound speed as free model parameters and then use the currently available cosmic observational data sets, which include type Ia supernova Union 2.1, baryon acoustic oscillation and WMAP 7-year data of cosmic background radiation, to constrain the possible entropic perturbations and the adiabatic sound speed via the Markov Chain Monte Carlo method. The results show that the cosmic observations favor a small effective sound speed $c^2_{s,eff}=0.00155_{- 0.00155}^{+ 0.000319}$ in $1\sigma$ region.Comment: 7 pages, 5 figures, to appear in Phys. Rev.

The productivity effects of decentralized reforms - an analysis of the Chinese industrial reforms

The empirical literature on the effects of ownership has not distinguished between the effects of ownership and the effects of control. It has also generally ignored the dynamic effects of various ownership and control rights. Using a rich set of panel data about changes in China's state-owned enterprises, the author examines the static and dynamic effects of decentralizing ownership and control rights. He finds that productivity and growth rates improved significantly when reform improved the incentives for managers and employees to learn and to work hard - for example by decentralizing the rights to control wages, make production decisions, and appoint new managers. Increasing profit-retention rates and adopting performance contracts - conventionally viewed as the most important reforms for China's state enterprises - did not improve productivity much. Overall, decentralization accounted for a least 42 percent of productivity growth in Chinese state enterprises in the 1980s. Much of that gain came from improvements in the growth rate of productivity rather than in improved levels of productivity.Labor Policies,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Public Health Promotion,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Health Monitoring&Evaluation,Municipal Financial Management