214,150 research outputs found

    Cosmological model of the interaction between dark matter and dark energy

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    In this paper, we test the dark matter-dark energy interacting cosmological model with a dynamic equation of state wDE(z)=w0+w1z/(1+z)w_{DE}(z)=w_{0}+w_{1}z/(1+z), using type Ia supernovae (SNe Ia), Hubble parameter data, baryonic acoustic oscillation (BAO) measurements, and the cosmic microwave background (CMB) observation. This interacting cosmological model has not been studied before. The best-fitted parameters with 1σ1 \sigma uncertainties are δ=0.022±0.006\delta=-0.022 \pm 0.006, ΩDM0=0.213±0.008\Omega_{DM}^{0}=0.213 \pm 0.008, w0=1.210±0.033w_0 =-1.210 \pm 0.033 and w1=0.872±0.072w_1=0.872 \pm 0.072 with χmin2/dof=0.990\chi^2_{min}/dof = 0.990. At the 1σ1 \sigma confidence level, we find δ<0\delta<0, which means that the energy transfer prefers from dark matter to dark energy. We also find that the SNe Ia are in tension with the combination of CMB, BAO and Hubble parameter data. The evolution of ρDM/ρDE\rho_{DM}/\rho_{DE} indicates that this interacting model is a good approach to solve the coincidence problem, because the ρDE\rho_{DE} decrease with scale factor aa. The transition redshift is ztr=0.63±0.07z_{tr}=0.63 \pm 0.07 in this model.Comment: 6 pages, 6 figures, published in A&

    Study of glass preforms for glass fiber optics applications (study of space processing of ceramic materials)

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    The feasibility, and technical and economic desirability was studied of space processing of glass preforms for optical fiber transmission applications. The results indicate that space processing can produce glass preforms of equal quality at lower cost than earth bound production, and can produce diameter modulation in the glass preform which promotes mode coupling and lowers the dispersion. The glass composition can be modified through the evaporative and diffusion processes, and graded refractive index profiles can be produced. A brief summary of the state of the art in optical fiber transmission is included