# Condensed Matter Theory

This research programme studies collective effects in quantum and classical many-body systems. Individual research lines in this area are interwoven in many ways.

A variety of aspects of Quantum Matter are studied, with emphasis on cold atomic matter and on quantum information / quantum computation. Recent topics have been (i) quantitative measures of entanglement in quantum matter (ii) the characterization of quantum critical behavior in the quantum Hall effect (joint with WZI), and (iii) topological phases and topological quantum computation.

The use of integrability has played a major role in the past, and will do so in the future. Increasingly it is used in combination with other methods in order to make predictions that are experimentally accessible (work on quantum magnets and on the D=1 Bose gas, the latter in collaboration with the quantum gases group of the WZI). On this subject a proposal for a joint research program with the KdV institute for mathematics is in preparation.

The institute is prominent in mathematical physics, both in the application of mathematical techniques to physical systems, and in finding mathematically relevant results from the study of physical models. Recent examples concern Stochastic Löwner Evolution (SLE) and the interesting ramifications in mathematics of studies of supersymmetric lattice models. The research theme ‘mathematical physics’ is by no means restricted to Program 2: very similar issues are explored in the context of high-energy physics.

In the area of Complex Systems, the institute has initiated research in the properties of granular matter. This has moved from granular gases to granular solids, and will be continued with the investigation of yield/jamming behavior and sound in granular media. Part of this research is done in collaboration with the Soft Matter group of the WZI.