A Holographic Quantum Critical Point at Finite Magnetic Field and Finite Density

We analyze the phase diagram of N=4 supersymmetric Yang-Mills theory with fundamental matter in the presence of a background magnetic field and nonzero baryon number. We identify an isolated quantum critical point separating two differently ordered finite density phases. The ingredients that give rise to this transition are generic in a holographic setup, leading us to conjecture that such critical points should be rather common. In this case, the quantum phase transition is second order with mean-field exponents. We characterize the neighborhood of the critical point at small temperatures and identify some signatures of a new phase dominated by the critical point. We also identify the line of transitions between the finite density and zero density phases. The line is completely determined by the mass of the lightest charged quasiparticle at zero density. Finally, we measure the magnetic susceptibility and find hints of fermion condensation at large magnetic field.Comment: 29 pages, 8 figure

Developing Artificial Herders Using Jason

This paper gives an overview of a proposed strategy for the "Cows and Herders" scenario given in the Multi-Agent Programming Contest 2009. The strategy is to be implemented using the Jason platform, based on the agent-oriented programming language Agent-Speak. The paper describes the agents, their goals and the strategies they should follow. The basis for the paper and for participating in the contest is a new course given in spring 2009 and our main objective is to show that we are able to implement complex multi-agent systems with the knowledge gained in an introductory course on multi-agent systems.Comment: 5 page