Cosmological constraint from QSO spatial power spectrum

In this paper we consider constraints on the cosmological density parameters from the spatial power spectrum of QSOs. We first review an analytic approach to the spatial power spectrum of QSOs, then we compare the result of the analytic approach with a preliminary result of the power spectrum from the two-degree Field QSO redshift (2QZ) survey. From a simple chi^2 test, we show that a finite baryon fraction better explains observation of the QSO power spectrum, which might suggest a possible detection of the baryonic oscillations in the QSO power spectrum.Comment: 3 pages, 1 figure, to appear in the proceedings of the conference "Lighthouses of the Universe: The Most Luminous Celestial Objects and Their Use for Cosmology", Garching, August 2001 (Springer-Verlag

Possible Method to Reconstruct the Cosmic Equation of State from Strong Gravitational Lensing Systems

A possible method to reconstruct the cosmic equation of state using strong gravitational lensing systems is proposed. The feasibility of the method is investigated by carrying out the reconstruction on the basis of a simple Monte-Carlo simulation. We show that the method can work and that the cosmic equation of state $w(z)$ can be determined within errors of $\Delta w\sim \pm0.1$ -- $\pm0.2$ when a sufficiently large number of lensing systems ($N\sim 20$) for z\simlt 1 are precisely measured. Statistics of lensed sources in a wide and deep survey like the SDSS are also briefly discussed.Comment: 12 pages including 3 figures, to be published in Prog. Theor. Phy