20 research outputs found
Weak Lensing and Dark Energy
We study the power of upcoming weak lensing surveys to probe dark energy.
Dark energy modifies the distance-redshift relation as well as the matter power
spectrum, both of which affect the weak lensing convergence power spectrum.
Some dark-energy models predict additional clustering on very large scales, but
this probably cannot be detected by weak lensing alone due to cosmic variance.
With reasonable prior information on other cosmological parameters, we find
that a survey covering 1000 sq. deg. down to a limiting magnitude of R=27 can
impose constraints comparable to those expected from upcoming type Ia supernova
and number-count surveys. This result, however, is contingent on the control of
both observational and theoretical systematics. Concentrating on the latter, we
find that the {\it nonlinear} power spectrum of matter perturbations and the
redshift distribution of source galaxies both need to be determined accurately
in order for weak lensing to achieve its full potential. Finally, we discuss
the sensitivity of the three-point statistics to dark energy.Comment: 16 pages, revtex. Peacock-Dodds PS used for all w, which weakens the
constraints. Tomography sec. expanded, estimate included of how well
systematics need to be controlle
Preparation of SiO2 Glass from Model Powder Compacts: III, Enhanced Densification by Sol Infiltration
Effect of body colour of Oreochromis mossambicus (Peters) on predation by largemouth bass, Micropterus salmoides (LacepĂšde)
Comparative Annulus Formation on Anatomical Structures of the White Sucker, Catostomus commersoni (LacépÚde)
Effect of Pore Distribution on Microstructure Development: II, First- and Second-Generation Pores
High-temperature creep and the interfacial mechanical response of a ceramic matrix composite
Structural superplasticity at higher strain rates of hypereutectoid Fe-5.5Al-1Sn-1Cr-1.3C steel
A fine-grained ultra-high-carbon steelâUHC steelâcontaining 1.35 wt pct carbon, 5.5 wt pct aluminum, 1 wt pct tin, and 1 wt pct chromium exhibits fine-structure superplasticity in the temperature regime between 775 °C and 900 °C at higher strain rates up to 10â2 sâ1. Thermomechanical processing was performed in order to achieve a fine-grained equiaxed microstructure consisting of Îș-carbides of about 0.7 to 2.5 ”m in size finely distributed within the ferritic Fe(Al, Sn, Cr) solid solution matrix with a linear intercept grain size of 3 to 5 ”m. Superplasticity occurred in the strain rate regime of 10â4<- [(e)\dot]â€10â2 sâ1 with m values of 0.5 to 0.6 (stress exponent n=1.6 to 2). Tensile elongations of more than 900 pct were recorded. From thermal activation analysis, activation energies of Q=230 to 243 kJ/mole were determined, which clearly reveal a contribution of the alloying elements Al and Sn to the lattice diffusion of iron. The governing deformation mechanism is grain boundary sliding accommodated by dislocation climb controlled by lattice diffusion sustained by chemical diffusion. At very high strain rates of [(e)\dot]âł2 · 10â2 sâ1, the strain-rate-sensitivity exponent decreases to about 0.2â€mâ€0.27, which indicates class II solid solution behavior of this material.Peer reviewe