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.

Evolution and Nucleosynthesis of Very Massive Primordial Stars

We investigate the evolution, final fate, and nucleosynthetic yields of rotating and non-rotating very massive stars (VMS) of zero metallicity. First we address the issue of mass loss during hydrogen burning due to vibrational instabilities. We find that these objects are much more stable than what was found in previous studies of VMS of solar composition, and expect only negligible mass loss driven by the pulsations. As these stars thus reach the end of their evolution with massive helium cores, they encounter the pair-creation instability. We find that for helium core masses of ~64...133 solar masses these stars are completely disrupted with explosion energies of up to ~1E53 erg and eject up to ~60 solar masses of Ni56 Stars with more massive helium cores collapse into black holes. We present the first calculations that follow the collapse of such a massive rotating star and predict that X-ray burst and significant gravitational wave emission could result.Comment: 4 pages, 1 figure, LaTeX, requires espcrc1.sty. To appear in Nucl. Phys. A., the proceedings of the conference "Nuclei in the Cosmos 2000", held in Aarhus, Denmark, June 27-July 1, 200

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

A line-binned treatment of opacities for the spectra and light curves from neutron star mergers

The electromagnetic observations of GW170817 were able to dramatically increase our understanding of neutron star mergers beyond what we learned from gravitational waves alone. These observations provided insight on all aspects of the merger from the nature of the gamma-ray burst to the characteristics of the ejected material. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called kilonovae or macronovae. Characteristics of the ejecta include large velocity gradients, relative to supernovae, and the presence of heavy $r$-process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. For example, these opacities include a dense forest of bound-bound features arising from near-neutral lanthanide and actinide elements. Here we investigate the use of fine-structure, line-binned opacities that preserve the integral of the opacity over frequency. Advantages of this area-preserving approach over the traditional expansion-opacity formalism include the ability to pre-calculate opacity tables that are independent of the type of hydrodynamic expansion and that eliminate the computational expense of calculating opacities within radiation-transport simulations. Tabular opacities are generated for all 14 lanthanides as well as a representative actinide element, uranium. We demonstrate that spectral simulations produced with the line-binned opacities agree well with results produced with the more accurate continuous Monte Carlo Sobolev approach, as well as with the commonly used expansion-opacity formalism. Additional investigations illustrate the convergence of opacity with respect to the number of included lines, and elucidate sensitivities to different atomic physics approximations, such as fully and semi-relativistic approaches.Comment: 27 pages, 22 figures. arXiv admin note: text overlap with arXiv:1702.0299

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