Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

While many models have been proposed for GRBs, those currently favored are all based upon the formation of and/or rapid accretion into stellar mass black holes. We present population synthesis calculations of these models using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distance for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. For reasonable assumptions regarding the many uncertainties in population synthesis, we calculate a daily event rate in the universe for i) merging neutron stars: ~100/day; ii) neutron-star black hole mergers: ~450/day; iii) collapsars: ~10,000/day; iv) helium star black hole mergers: ~1000/day; and v) white dwarf black hole mergers: ~20/day. The range of uncertainty in these numbers however, is very large, typically two to three orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, half of the DNS and BH/NS mergers will happen within 60kpc (for a Milky-Way massed galaxy) to 5Mpc (for a galaxy with negligible mass) from the galactic center. Because of the delay time, neutron star and black hole mergers will happen at a redshift 0.5 to 0.8 times that of the other classes of models. Information is still lacking regarding the hosts of short hard bursts, but we suggest that they are due to DNS and BH/NS mergers and thus will ultimately be determined to lie outside of galaxies and at a closer mean distance than long complex bursts (which we attribute to collapsars).Comment: 57 pages total, 23 figures, submitted by Ap

Affirmative Action and Its Mythology

For more than three decades, critics and supporters of affirmative action have fought for the moral high ground ­ through ballot initiatives and lawsuits, in state legislatures, and in varied courts of public opinion. The goal of this paper is to show the clarifying power of economic reasoning to dispel some myths and misconceptions in the racial affirmative action debates. We enumerate seven commonly held (but mistaken) views one often encounters in the folklore about affirmative action (affirmative action may involve goals and timelines, but definitely not quotas, e.g.). Simple economic arguments reveal these seven views to be more myth than fact.

Color-Blind Affirmative Action

This paper presents a conceptual framework for understanding the consequences of the widespread adoption of race-neutral alternatives' to conventional racial affirmative action policies in college admissions. A simple model of applicant competition with endogenous effort is utilized to show that, in comparison to color-conscious affirmative action, these color-blind alternatives can significantly lower the efficiency of the student selection process in equilibrium. We examine data on matriculates at several selective colleges and universities to estimate the magnitudes involved. It is shown that the short-run efficiency losses of implementing color-blind affirmative action (in our sample) are four to five times as high as color-conscious affirmative action.

State Trends in Premiums and Deductibles, 2003-2010: The Need for Action to Address Rising Costs

Examines the rise in employer-based insurance premiums and deductibles and as a percentage of median household income. Projects average family coverage premiums in 2020 if federal health reform is not implemented and historical rates of increase continue