119097611
Measuring the flatness of focal plane for very large mosaic CCD camera
Large mosaic multiCCD camera is the key instrument for modern digital sky survey. DECam is an extremely red sensitive 520 Megapixel camera designed for the incoming Dark Energy Survey (DES). It is consist of sixty two 4k2k and twelve 2k2k 250-micron thick fully-depleted CCDs, with a focal plane of 44 cm in diameter and a eld of view of 2.2 square degree. It will be attached to the Blanco 4-meter telescope at CTIO. The DES will cover 5000 square-degrees of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years starting from 2011. To achieve the science goal of constraining the Dark Energy evolution, stringent requirements are laid down for the design of DECam. Among them, the atness of the focal plane needs to be controlled within a 60-micron envelope in order to achieve the specied PSF variation limit. It is very challenging to measure the atness of the focal plane to such precision when it is placed in a high vacuum dewar at 173 K. We developed two image based techniques to measure the atness of the focal plane. By imaging a regular grid of dots on the focal plane, the CCD oset along the optical axis is converted to the variation the grid spacings at dierent positions on the focal plane. After extracting the patterns and comparing the change in spacings, we can measure the atness to high precision. In method 1, the regular dots are kept in high sub micron precision and cover the whole focal plane. In method 2, no high precision for the grid is required. Instead, we use a precise XY stage moves the pattern across the whole focal plane and comparing the variations of the spacing when it is imaged by dierent CCDs. Simulation and real measurements show that the two methods work very well for our purpose, and are in good agreement with the direct optical measurements.
121863790
A New Exactly Solvable Inflation Model and Its Power Spectrum
We present a new exactly solvable inflation model in which inflation can stop automatically, and in the approximately de Sitter limit, we give its power spectrum which can be tested in the future observations of cosmic microwave background anisotropy.
119458029
O(N) Quintessence with a Cosine-Type Potential
We propose a quintessence model with a cosine-type potential, in which the scalar field Φa possesses an O(N) internal symmetry. The most prominent feature of this model is that it will not reduce to a cosmological constant even when |Φa| is spatially uniform and time-independent. Since different values of the potential parameter will lead to different cosmic microwave background anisotropies, which may be detectable in future satellite experiments, one can decide by observations whether the cosine-type quintessence consists of one scalar field or many fields with a symmetry constraint.
198140971
Charged D stars
We describe charged soliton stars with a solid angular deficit (charged boson D stars), and find the approximate solution in the external space. Besides, we discuss the stability of charged D stars and find when the number of bosons is less than certain value, charged D stars are quantum mechanically stable.
7857108
Cosmological dynamics of scalar fields with O(N) symmetry
In this paper, we study the cosmological dynamics of scalar fields with O(N) symmetry in general potentials. We compare the phase space of the dynamical systems of the quintessence and phantom and give the conditions for the existence of various attractors as well as their cosmological implications. We also show that the existence of a tracking attractor in O(N) phantom models requires the potential with Γ < 1/2, which makes the model with exponential potential possess no tracking attractor.
199673346
Generalized quartessence cosmic dynamics: phantom or quintessence with de Sitter attractor
119202826
Sunyaev-Zel’dovich signal of the maxBCG SDSS galaxy clusters in WMAP
The Planck Collaboration measured the Sunyaev-Zel'dovich (SZ) decrement of optically selected clusters from the Sloan Digital Sky Survey, finding that it falls significantly below expectations based on existing mass calibration of the maxBCG galaxy clusters. Resolving this tension requires either the data to go up, or the theoretical expectations to come down. Here, we use data from the Wilkinson Microwave Anisotropy Probe (WMAP) to perform an independent estimate of the SZ decrement of maxBCG clusters. The recovered signal is consistent with that obtained using Planck, though with larger error bars due to WMAP's larger beam size and smaller frequency range. Nevertheless, this detection serves as an independent confirmation of the magnitude of the effect, and demonstrates that the observed discrepancy must be theoretical in origin.