Secondary Electron Yield Measurements of Fermilab's Main Injector Vacuum Vessel

We discuss the progress made on a new installation in Fermilab's Main Injector that will help investigate the electron cloud phenomenon by making direct measurements of the secondary electron yield (SEY) of samples irradiated in the accelerator. In the Project X upgrade the Main Injector will have its beam intensity increased by a factor of three compared to current operations. This may result in the beam being subject to instabilities from the electron cloud. Measured SEY values can be used to further constrain simulations and aid our extrapolation to Project X intensities. The SEY test-stand, developed in conjunction with Cornell and SLAC, is capable of measuring the SEY from samples using an incident electron beam when the samples are biased at different voltages. We present the design and manufacture of the test-stand and the results of initial laboratory tests on samples prior to installation.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012) 20-25 May 2012, New Orleans, Louisian

Cosmological perturbations in a healthy extension of Horava gravity

In Horava's theory of gravity, Lorentz symmetry is broken in exchange for renormalizability, but the original theory has been argued to be plagued with problems associated with a new scalar mode stemming from the very breaking of Lorentz symmetry. Recently, Blas, Pujolas, and Sibiryakov have proposed a healthy extension of Horava gravity, in which the behavior of the scalar mode is improved. In this paper, we study scalar modes of cosmological perturbations in extended Horava gravity. The evolution of metric and density perturbations is addressed analytically and numerically. It is shown that for vanishing non-adiabatic pressure of matter the large scale evolution of cosmological perturbations converges to that described by a single constant, $\zeta$, which is an analog of a curvature perturbation on the uniform-density slicing commonly used in usual gravitational theories. The subsequent evolution is thus determined completely by the value of $\zeta$.Comment: 10 pages, 4 figures; v2: published versio

Macroeconomic Fluctuations, Inequality, and Human Development

This paper examines the two-way relationship between inequality and economic fluctuations, and the implications for human development. For years, the dominant paradigm in macroeconomics, which assumed that income distribution did not matter, at least for macroeconomic behavior, ignored inequality--both its role in causing crises and the effect of fluctuations in general, and crises in particular, on inequality. But the most recent financial crisis has shown the errors in this thinking, and these views are finally beginning to be questioned. Economists who had looked at the average equity of a homeowner--ignoring the distribution--felt comfortable that the economy could easily withstand a large fall in housing prices. When such a fall occurred, however, it had disastrous effects, because a large fraction of homeowners owed more on their homes than the value of the home, leading to waves of foreclosure and economic stress. Policy-makers and economists alike have begun to take note: inequality can contribute to volatility and the creation of crises, and volatility can contribute to inequality. Here, we explore the variety of channels through which inequality affects fluctuations and fluctuations affect inequality, and explore how some of the changes in our economy may have contributed to increased inequality and volatility both directly and indirectly. After describing the two-way relationship, the paper discusses hysteresis--the fact that the consequences of an economic downturn can be long-lived. Then, it examines how policy can either mitigate or exacerbate the inequality consequences of economic downturns, and shows how well-intentioned policies can sometimes be counterproductive. Finally, it links these issues to human development, especially in developing countries

License prices for financially constrained firms

It is often alleged that high auction prices inhibit service deployment. We investigate this claim under the extreme case of financially constrained bidders. If demand is just slightly elastic, auctions maximize consumer surplus if consumer surplus is a convex function of quantity (a common assumption), or if consumer surplus is concave and the proportion of expenditure spent on deployment is greater than one over the elasticity of demand. The latter condition appears to be true for most of the large telecom auctions in the US and Europe. Thus, even if high auction prices inhibit service deployment, auctions appear to be optimal from the consumers’ point of view