Monte Carlo studies of the Ising square lattice with competing interactions

We use improved Monte-Carlo algorithms to study the antiferromagnetic 2D-Ising model with competing interactions $J_1$ on nearest neighbour and $J_2$ on next-nearest neighbour bonds. The finite-temperature phase diagram is divided by a critical point at $J_2 = J_1/2$ where the groundstate is highly degenerate. To analyse the phase boundaries we look at the specific heat and the energy distribution for various ratios of $J_2/J_1$. We find a first order transition for small $J_2 > J_1/2$ and the transition temperature suppressed to $T_C=0$ at the critical point.Comment: 4 pages, 4 figures, accepted for publication in the proceedings of the conference on Highly Frustrated Magnets 2008 in Braunschwei

Phase diagram of the Ising square lattice with competing interactions

We restudy the phase diagram of the 2D-Ising model with competing interactions $J_1$ on nearest neighbour and $J_2$ on next-nearest neighbour bonds via Monte-Carlo simulations. We present the finite temperature phase diagram and introduce computational methods which allow us to calculate transition temperatures close to the critical point at $J_2 = 0.5 J_1$. Further on we investigate the character of the different phase boundaries and find that the transition is weakly first order for moderate $J_2 > 0.5 J_1$.Comment: 5 pages including 6 figures, accepted for publication in EPJ

Quantum disordered ground state for the frustrated square lattice

We present Quantum Monte-Carlo simulations of an exchange-anisotropic spin-1/2 Heisenberg model on a square lattice with nearest and next-nearest neighbor interactions. The ground state phase diagram shows two classical magnetically ordered phases for dominating antiferromagnetic S^z-interactions and for large quantum fluctuations a ferromagnetic order in the x-y plane. In between a finite region is detected where neither classical nor quantum mechanical order, e.g. long-ranged dimer correlations, are found.Comment: 4 pages, 4 figures, proceedings SCES 201

New learning opportunities in a networked world: developing a research agenda on innovative uses of ICTS for learning and teaching

IDRC Project Title: Developing a Research Agenda on Expanding New Digital Learning Opportunities in Developing Countries;IDRC Project Number: 107628The report describes outcomes of the activities carried out for the project “New Learning Opportunities in a Networked World: Developing a Research Agenda on Innovative uses of ICTs for Learning and Teaching”. The research consists of three main activities, namely desk research, written expert consultation and group concept mapping study involving a 2-day workshop and a follow-up with experts who could not attend the workshop. These activities are interconnected elements of the consultative approach to establishing a research agenda.International Development Research Centre (IDRC), Canad

Mindergie: A pervasive learning game for pro-environmental behaviour at the workplace

This chapter reports about a pervasive learning game to increase the environmental awareness and pro-environmental behaviour at the workplace. Based on a discussion of the theoretical background and related work we introduce the game design and game elements. Results of a formative evaluation study are presented and discussed. Results show that incentive mechanisms are less important than challenging game components that involve employees in proposing solutions for energy conservation at the workplace. Conclusions are drawn for future games and energy conservation activities at the workplace.This project has been partially funded by a SURFnet innovation grant for sustainable ICT solutions and partially by the Welten Institute – Research Centre for Learning, Teaching and Technology of the Open University of the Netherlands