Hyperelliptic Theta-Functions and Spectral Methods

A code for the numerical evaluation of hyperelliptic theta-functions is presented. Characteristic quantities of the underlying Riemann surface such as its periods are determined with the help of spectral methods. The code is optimized for solutions of the Ernst equation where the branch points of the Riemann surface are parameterized by the physical coordinates. An exploration of the whole parameter space of the solution is thus only possible with an efficient code. The use of spectral approximations allows for an efficient calculation of all quantities in the solution with high precision. The case of almost degenerate Riemann surfaces is addressed. Tests of the numerics using identities for periods on the Riemann surface and integral identities for the Ernst potential and its derivatives are performed. It is shown that an accuracy of the order of machine precision can be achieved. These accurate solutions are used to provide boundary conditions for a code which solves the axisymmetric stationary Einstein equations. The resulting solution agrees with the theta-functional solution to very high precision.Comment: 25 pages, 12 figure

A Longitudinal Analysis of Cars, Transit, and Employment Outcomes

Access to cars and transit can influence individuals’ ability to reach opportunities such as jobs, health care, and other important activities. While access to cars and public transit varies considerably across time, space, and across populations, most research portrays car access as a snapshot in time; some people have a car and others do not. But does this snapshot approach mask variation in car ownership over time? And how does access to particular types of transportation resources influence individuals’ economic outcomes? The authors improve upon existing research by using panel data from 1999 to 2013 from the Panel Study of Income Dynamics (PSID) to examine levels of automobile access in groups that have variable access: poor families, immigrants, and people of color. They further employ two new national datasets of access to jobs using public transit. These datasets are used to examine the effect of transit and automobile access on income growth over time within families, controlling for a number of relevant variables. The research found that for most families, being “carless” is a temporary condition. While 13% of families in the US are carless in any given year, only 5% of families are carless for all seven waves of data examined in the analysis. The research also found that poor families, immigrants, and people of color (particularly blacks) are considerably more likely to transition into and out car owner-ship frequently and are less likely to have a car in any survey year than are non-poor families, the US-born, and whites. The research also found that improving automobile access is associated with a decreased probability of future unemployment and is associated with greater income gains. However, the analysis suggests that the costs of owning and maintaining a car may be greater than the income gains associated with in-creased car ownership. The relationship between public transit and improved economic outcomes is less clear. The research found that living in areas with access to high-quality public transportation has no relationship with future earnings. However, transit serves an important purpose in providing mobility for those who cannot or choose not to own a car

Further application of a semi-microscopic core-particle coupling method to the properties of Gd155,157, and Dy159

In a previous paper a semi-microscopic core-particle coupling method that includes the conventional strong coupling core-particle model as a limiting case, was applied to spectra and electromagnetic properties of several well-deformed odd nuclei. This work, coupled a large single-particle space to the ground state bands of the neighboring even cores. In this paper, we generalize the theory to include excited bands of the cores, such as beta and gamma bands, and thereby show that the resulting theory can account for the location and structure of all bands up to about 1.5 MeV.Comment: 15 pages including 9 figure(postscript), submitted to Phys.Rev.

Cartel destabilization and leniency programs: Empirical evidence

Leniency programs as a tool for cartel detection and cartel destabilization, have been implemented since the early nineties. Theoretical work has shown that leniency programs can be effective in enhancing cartel detection and deterrence, but these effects are not straight-forward. It is even possible that there is an increase in the total number of cartels. Empirical evidence shows that the positive effect on cartel deterrence seems to dominate, but cannot provide definite evidence, as inference is derived only by detected cartels. This study uses a more direct measure of success, the intensity of competition at the industry level of OECD countries. An instrumental variable approach, reveals a positive effect on industries' competition intensity of leniency programs indicating effectiveness in cartel destabilization and effective deterrence. --Cartel,Antitrust,Leniency Program

Applications of model structure determination to flight test data

Several statistical and information criteria need to be considered when selecting an adequate model. Incorrect stability and control derivates result from inadequate aerodynamic model structure. Stepwise regression is used to determine the structure for an adequate model. Flight data which covers a nonlinear aerodynamic model range may be analyzed as a single data set or partitioned into several distinct sets. Stepwise regression for model structure detemination and parameter estimation was successfully applied to three aircraft types (single engine general aviation, unaugmented modern jet fighter, jet transport)