Accurate Evolution of Orbiting Binary Black Holes

We present a detailed analysis of binary black hole evolutions in the last orbit, and demonstrate consistent and convergent results for the trajectories of the individual bodies. The gauge choice can significantly affect the overall accuracy of the evolution. It is possible to reconcile certain gauge dependent discrepancies by examining the convergence limit. We illustrate these results using an initial data set recently evolved by Bruegmann (Phys. Rev. Lett. 92, 211101). For our highest resolution and most accurate gauge, we estimate the duration of this data set's last orbit to be approximately $59 M_{ADM}$.Comment: 4 pages, 3 figure

Wavelet Domain Geophysical Inversion

We present a non-linear method for solving linear inverse problems by thresholding coefficients in the wavelet domain1. Our method is based on the wavelet-vaguelette decomposition of Donoho (1992). Numerical results for a synthetic travel-time inversion problem show that the wavelet based method outperforms traditional least-squares methods of solution.Massachusetts Institute of Technology. Earth Resources Laborator

Wavelet domain linear inversion with application to well logging

Solving linear inversion problems in geophysics is a major challenge when dealing with non-stationary data. Certain non-stationary data sets can be shown to lie in Besov function spaces and are characterized by their smoothness (differentiability) and two other parameters. This information can be input into an inverse problem by posing the problem in the wavelet domain. Contrary to Fourier transforms, wavelets form an unconditional basis for Besov spaces, allowing for a new generation of linear inversion schemes which incorporate smoothness information more precisely. As an example inversion is performed on smoothed and subsampled well log data

Is it a norm to favour your own group?

This paper examines the relationship between norm enforcement and in-group favouritism behaviour. Using a new two-stage allocation experiment with punishments, we investigate whether in-group favouritism is considered as a social norm in itself or as a violation of a different norm, such as egalitarian norm. We find that which norm of behaviour is enforced depends on who the punisher is. If the punishers belong to the in-group, in-group favouritism is considered a norm and it does not get punished. If the punishers belong to the out-group, in-group favouritism is frequently punished. If the punishers belong to no group and merely observe in-group favouritism (the third-party), they do not seem to care sufficiently to be willing to punish this behaviour. Our results shed a new light on the effectiveness of altruistic norm enforcement when group identities are taken into account and help to explain why in-group favouritism is widespread across societies

Geostatistical Seismic Inversion Using Well Log Constraints

Information about reservoir properties usually comes from two sources: seismic data and well logs. The former provide an indirect, low resolution image of rock velocity and density. The latter provide direct, high resolution (but laterally sparse) sampling of these and other rock parameters. An important problem in reservoir characterization is how best to combine these data sets, allowing the well information to constrain the seismic inversion and, conversely, using the seismic data to spatially interpolate and extrapolate the well logs. We have developed a seismic/well log inversion method that combines geostatistical methods for well log interpolation (i.e., kriging) with a Monte Carlo search technique for seismic inversion. Our method follows the approach used by Haas and Dubrule (1994) in their sequential inversion algorithm. Kriging is applied to the well data to obtain velocity estimates and their variances for use as a priori constraints in the seismic inversion. Further, inversion of a complete 2-D seismic section is performed one trace at a time. The velocity profiles derived from previous seismic traces are incorporated as "pseudo well logs" in subsequent applications of kriging. Our version of this algorithm employs a more efficient Monte Carlo search algorithm in the seismic inversion step, and moves progressively away from the wells so as to minimize the kriging variance at each step. Numerical experiments with synthetic data demonstrate the viability of our seismic/well data inversion scheme.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation Consortiu