Sensitivity of galaxy cluster dark energy constraints to halo modeling uncertainties

We perform a sensitivity study of dark energy constraints from galaxy cluster surveys to uncertainties in the halo mass function, bias and the mass-observable relation. For a set of idealized surveys, we evaluate cosmological constraints as priors on sixteen nuisance parameters in the halo modeling are varied. We find that surveys with a higher mass limit are more sensitive to mass-observable uncertainties while surveys with low mass limits that probe more of the mass function shape and evolution are more sensitive to mass function errors. We examine the correlations among nuisance and cosmological parameters. Mass function parameters are strongly positively (negatively) correlated with Omega_DE (w). For the mass-observable parameters, Omega_DE is most sensitive to the normalization and its redshift evolution while w is more sensitive to redshift evolution in the variance. While survey performance is limited mainly by mass-observable uncertainties, the current level of mass function error is responsible for up to a factor of two degradation in ideal cosmological constraints. For surveys that probe to low masses (10^13.5 h^-1 M_sun), even percent-level constraints on model nuisance parameters result in a degradation of ~ sqrt{2} (2) on Omega_DE (w) relative to perfect knowledge.Comment: 13 pages, 5 figures, accepted by PR

Sound propagation from a simple source in a wind tunnel

The nature of the acoustic field of a simple source in a wind tunnel under flow conditions was examined theoretically and experimentally. The motivation of the study was to establish aspects of the theoretical framework for interpreting acoustic data taken (in wind) tunnels using in wind microphones. Three distinct investigations were performed and are described in detail

Inorganic glass ceramic slip rings

Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours

Low friction magnetic recording tape Patent

Development of low friction magnetic recording tap

Star cluster formation history along the minor axis of the Large Magellanic Cloud

We analysed Washington $CMT_1$ photometry of star clusters located along the minor axis of the LMC, from the LMC optical centre up to $\sim$ 39 degrees outwards to the North-West. The data base was exploited in order to search for new star cluster candidates, to produce cluster CMDs cleaned from field star contamination and to derive age estimates for a statistically complete cluster sample. We confirmed that 146 star cluster candidates are genuine physical systems, and concluded that an overall $\sim$ 30 per cent of catalogued clusters in the surveyed regions are unlikely to be true physical systems. We did not find any new cluster candidates in the outskirts of the LMC (deprojected distance $\ge$ 8 degrees). The derived ages of the studied clusters are in the range 7.2 < log($t$ yr$^{-1}$) $\le$ 9.4, with the sole exception of the globular cluster NGC\,1786 (log($t$ yr$^{-1}$) = 10.10). We also calculated the cluster frequency for each region, from which we confirmed previously proposed outside-in formation scenarios. In addition, we found that the outer LMC fields show a sudden episode of cluster formation (log($t$ yr$^{-1}$) $\sim$ 7.8-7.9) that continued until log($t$ yr$^{-1}$) $\sim$ 7.3 only in the outermost LMC region. We link these features to the first pericentre passage of the LMC to the MW, which could have triggered cluster formation due to ram pressure interaction between the LMC and MW halo.Comment: 13 pages, 4 figures. Accepted for publication in MNRA

Simulating study of the interaction between the propulsion and flight control systems of a subsonic lift fan VTOL

The possibility of interactions between the propulsion and flight control systems of a three-fan subsonic VTOL aircraft was studied using nonreal time simulation. Time histories of critical internal engine parameters were obtained and possible deleterious effects of engine dynamics on flight control were identified and analyzed. No deleterious effects, with the exception of the effects of the fan actuator deadband, were found. A method of alleviating these effects through feedback of the actuator output to the flight controller was developed

Aggregate returns to scale: why measurement is imprecise

The extent to which there are aggregate returns to scale at the level of aggregate production has important implications both for the types of shocks generating business cycles and for optimal policy. However, prior attempts to measure the extent of these returns using instrumental variable techniques have yielded quite imprecise estimates. In this article, we show that the production shocks implied by a range of returns to scale that encompasses both large increasing returns and large decreasing returns are almost identical. This makes clear that there is a fundamental reason for the imprecision of prior estimates and casts doubt on our ability to generate more precise estimatesBusiness cycles

Shrinking money and monetary business cycles

In the postwar period velocity has risen so sharply in the U.S. that the ratio of money to nominal output has fallen by a factor of three. We analyze the implications of shrinking money for the real effects of a monetary shock in two classes of equilibrium monetary business cycle models: limited participation (liquidity) models and predetermined (sticky) price models. We show that the liquidity model predicts that a rise in velocity leads to a substantial reduction in the real effects of a monetary shock. In sharp contrast, we show that the real effects of a monetary shock in the sticky price model are largely invariant to changes in velocity. We provide evidence that suggests that the real effects of monetary shocks have fallen over the postwar period.Business cycles

The Great Depression in the United States from a neoclassical perspective

Can neoclassical theory account for the Great Depression in the United States—both the downturn in output between 1929 and 1933 and the recovery between 1934 and 1939? Yes and no. Given the large real and monetary shocks to the U.S. economy during 1929–33, neoclassical theory does predict a long, deep downturn. However, theory predicts a much different recovery from this downturn than actually occurred. Given the period’s sharp increases in total factor productivity and the money supply and the elimination of deflation and bank failures, theory predicts an extremely rapid recovery that returns output to trend around 1936. In sharp contrast, real output remained between 25 and 30 percent below trend through the late 1930s. We conclude that a new shock is needed to account for the Depression’s weak recovery. A likely culprit is New Deal policies toward monopoly and the distribution of income.Depressions

Summary of the Structure Functions and Low-x working group

We report a summary of the structure function working group which covers a wide range of the recent results from HERA, Tevatron, RHIC, and JLab experiments, and many theoretical issues from low x to high x.Comment: 20 pages, presented at 13th International Workshop on Deep Inelastic Scattering (DIS 05), Madison, Wisconsin, 27 Apr - 1 May 200