Predicting the expected behavior of agents that learn about agents: the CLRI framework

We describe a framework and equations used to model and predict the behavior of multi-agent systems (MASs) with learning agents. A difference equation is used for calculating the progression of an agent's error in its decision function, thereby telling us how the agent is expected to fare in the MAS. The equation relies on parameters which capture the agent's learning abilities, such as its change rate, learning rate and retention rate, as well as relevant aspects of the MAS such as the impact that agents have on each other. We validate the framework with experimental results using reinforcement learning agents in a market system, as well as with other experimental results gathered from the AI literature. Finally, we use PAC-theory to show how to calculate bounds on the values of the learning parameters

Observation of anisotropic diamagnetism above the superconducting transition in iron-pnictide Ba_(1-x)K_xFe2As2 single crystals due to thermodynamic fluctuations

High resolution magnetization measurements performed in a high quality Ba_(1-x)K_xFe2As2 single crystal allowed to determine the diamagnetism induced above the superconducting transition by thermally activated Cooper pairs. These data, obtained with magnetic fields applied along and transverse to the crystal ab layers, demonstrate experimentally that the superconducting transition of iron pnictides may be explained at a phenomenological level in terms of the Gaussian Ginzburg-Landau approach for three-dimensional anisotropic superconductors.Comment: Final version with minor corrections. 6 pages, 4 figure

Classical simulation versus universality in measurement based quantum computation

We investigate for which resource states an efficient classical simulation of measurement based quantum computation is possible. We show that the Schmidt--rank width, a measure recently introduced to assess universality of resource states, plays a crucial role in also this context. We relate Schmidt--rank width to the optimal description of states in terms of tree tensor networks and show that an efficient classical simulation of measurement based quantum computation is possible for all states with logarithmically bounded Schmidt--rank width (with respect to the system size). For graph states where the Schmidt--rank width scales in this way, we efficiently construct the optimal tree tensor network descriptions, and provide several examples. We highlight parallels in the efficient description of complex systems in quantum information theory and graph theory.Comment: 16 pages, 4 figure

Non-equilibrium melting of colloidal crystals in confinement

We report on a novel and flexible experiment to investigate the non-equilibrium melting behaviour of model crystals made from charged colloidal spheres. In a slit geometry polycrystalline material formed in a low salt region is driven by hydrostatic pressure up an evolving gradient in salt concentration and melts at large salt concentration. Depending on particle and initial salt concentration, driving velocity and the local salt concentration complex morphologic evolution is observed. Crystal-melt interface positions and the melting velocity are obtained quantitatively from time resolved Bragg- and polarization microscopic measurements. A simple theoretical model predicts the interface to first advance, then for balanced drift and melting velocities to become stationary at a salt concentration larger than the equilibrium melting concentration. It also describes the relaxation of the interface to its equilibrium position in a stationary gradient after stopping the drive in different manners. We further discuss the influence of the gradient strength on the resulting interface morphology and a shear induced morphologic transition from polycrystalline to oriented single crystalline material before melting

Ideas, Institutions, Intervention, and Ethnic Conflict: A Constructivist Analysis of Russian Peacekeeping in the Former Soviet Union

Following the collapse of the Soviet Union in 1991, the fifteen union republics of the former superpower separated into newly independent sovereign states. The largest of these, the Russian Federation, has since emerged as the most capable and politically assertive and has inherited the majority of its predecessor’s geopolitical and strategic interests. Though Moscow’s interests in its “near-abroad” reflect the implications of its longstanding imperial legacy in the region, Russia entered the post-Soviet period pursuing a confused strategy of disengagement with regards to the new and unstable countries of the Former Soviet Union (FSU). Beginning in mid-1992 and continuing into late-1994, however, Russia began implementing a more assertive and interventionist response strategy to address the region’s growing instability. This project applies a combination of constructivism and historical institutionalist theory to demonstrate how, despite the Russian government’s early commitment to internationalist norms, fluid institutional preconditions allowed for a series of key structural shifts in the early post-Soviet period to drive administrative inertia away from the weakly institutionalized liberal-pacifist ideals of the Gorbachev era and towards a more muscular, nationalist, and zero-sum foreign policy strategy. In this context, the period from mid-1992 through late-1994 saw a rise in Russian intervention in the near abroad as intervening events challenged the orthodoxy of the isolationists in power and legitimized the efforts of revanchist policy entrepreneurs framing the use of force as a justifiable and necessary foreign policy strategy

When only two thirds of the entanglement can be distilled

We provide an example of distillable bipartite mixed state such that, even in the asymptotic limit, more pure-state entanglement is required to create it than can be distilled from it. Thus, we show that the irreversibility in the processes of formation and distillation of bipartite states, recently proved in [G. Vidal, J.I. Cirac, Phys. Rev. Lett. 86, (2001) 5803-5806], is not limited to bound-entangled states.Comment: 4 pages, revtex, 1 figur