Patents Hinder Collusion

We argue that a patent system makes collusion among innovators more difficult. Our simple argument is based on two properties of the patent system. First, a patent not only protects against infringement but also against retaliation by former collusion members. Second, a deviator has an equal chance with former collusion members to get a patent on new innovations. We show that if a patent system reduces spillovers, it renders collusion impossible. Moreover, it is possible to design a patent system that simultaneously increases knowledge spillovers and eliminates collusionPatens, Collusion, Secrecy, Innovation

Dynamical damping terms for symmetry-seeking shift conditions

Suitable gauge conditions are fundamental for stable and accurate numerical-relativity simulations of inspiralling compact binaries. A number of well-studied conditions have been developed over the last decade for both the lapse and the shift and these have been successfully used both in vacuum and non-vacuum spacetimes when simulating binaries with comparable masses. At the same time, recent evidence has emerged that the standard "Gamma-driver" shift condition requires a careful and non-trivial tuning of its parameters to ensure long-term stable evolutions of unequal-mass binaries. We present a novel gauge condition in which the damping constant is promoted to be a dynamical variable and the solution of an evolution equation. We show that this choice removes the need for special tuning and provides a shift damping term which is free of instabilities in our simulations and dynamically adapts to the individual positions and masses of the binary black-hole system. Our gauge condition also reduces the variations in the coordinate size of the apparent horizon of the larger black hole and could therefore be useful when simulating binaries with very small mass ratios.Comment: 11 pages, 8 figure

Matched Filtering of Numerical Relativity Templates of Spinning Binary Black Holes

Tremendous progress has been made towards the solution of the binary-black-hole problem in numerical relativity. The waveforms produced by numerical relativity will play a role in gravitational wave detection as either test-beds for analytic template banks or as template banks themselves. As the parameter space explored by numerical relativity expands, the importance of quantifying the effect that each parameter has on first the detection of gravitational waves and then the parameter estimation of their sources increases. In light of this, we present a study of equal-mass, spinning binary-black-hole evolutions through matched filtering techniques commonly used in data analysis. We study how the match between two numerical waveforms varies with numerical resolution, initial angular momentum of the black holes and the inclination angle between the source and the detector. This study is limited by the fact that the spinning black-hole-binaries are oriented axially and the waveforms only contain approximately two and a half orbits before merger. We find that for detection purposes, spinning black holes require the inclusion of the higher harmonics in addition to the dominant mode, a condition that becomes more important as the black-hole-spins increase. In addition, we conduct a preliminary investigation of how well a template of fixed spin and inclination angle can detect target templates of arbitrary spin and inclination for the axial case considered here

Can Altruism Hinder Cooperation?

This note considers the effects of altruism on cooperation in the context of a repeated Prisoner's Dilemma. Altruism has two conflicting impacts on cooperation: One is to reduce the temptation for defection the other is to make the future punishment ineffective. The total effect of altruism hinges on the shape of players'' cost functions.Continuous Prisoner's Dilemma