Risky Punishment and Reward in the Prisoner’s Dilemma

We conduct a prisoner’s dilemma experiment with a punishment/reward stage, where punishments and rewards are risky. This is compared with a risk free treatment. We find that subjects do not change their behavior in the face of risky outcomes. Additionally, we measure risk attitude and the emotions of subjects. While we find a strong influence of emotions, individual risk aversion has no effect on the decision to punish or reward. This is good news for lab experiments who abstract from risky outcomes. From the perspective of social preferences, our results provide evidence for risk neutral inclusion of other player’s payoffs in the decisionmaker’s utility function

A robust and efficient implementation of LOBPCG

Locally Optimal Block Preconditioned Conjugate Gradient (LOBPCG) is widely used to compute eigenvalues of large sparse symmetric matrices. The algorithm can suffer from numerical instability if it is not implemented with care. This is especially problematic when the number of eigenpairs to be computed is relatively large. In this paper we propose an improved basis selection strategy based on earlier work by Hetmaniuk and Lehoucq as well as a robust convergence criterion which is backward stable to enhance the robustness. We also suggest several algorithmic optimizations that improve performance of practical LOBPCG implementations. Numerical examples confirm that our approach consistently and significantly outperforms previous competing approaches in both stability and speed

A Space-Charge Neutralizing Plasma Channel for an Intense Beam

Ion bunches have been suggested as means to heat matter to the warm dense matter, or strongly coupled plasma regime (Temperature ~; 0.1 to 10 eV). For a K+ beam at 0.4 MeV, ~;1 J/cm2 is required to reach 1 eV in solid Aluminum. Also the pulse duration must be short (<~; 2 ns) to avoid hydrodynamic cooling. A spot radius ~;0.5 mm, and current ~;10 A are thus need to reach this flux level and pulse duration. Currents will be achieved by compressing the beam axially with an IBM. To further increase the beam intensity on target, an 8T field solenoid, filled with beam neutralizing plasma will be used. A plasma is injected from filtered cathodic arc plasma sources. The Neutralized Drift Compression Experiment (NDCX-1) at LBNL is intended to test these neutralized focusing techniques with the goal of reaching target temperatures ~;0.5 eV. Experimental measurements including the on axis plasma density distribution and, the beam density distribution, will be presented