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ETSF Correlation Team

The substantial growth in the number of researchers within the ETSF since its creation prompted the ETSF to adopt a new way of collaborating. In particular, its annual workshop had become too large for a dynamic collaborative research work. It appeared necessary to create smaller groups –collaboration teams- around challenges related to theoretical spectroscopy, sized for breakthroughs. Therefore several collaboration teams were created in 2010 such as the team working on electron correlation.

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The description, comprehension, and prediction of the effects of electron correlation in real materials is nowadays one of the greatest challenges for the theoreticians of condensed matter. The difficulty lies in the fact that one deals with so-called  many-body  phenomena, intrinsically due to the interaction among all the (~ $10^{23}$) electrons in a system.

A way to treat the many-body problem is to use Green's functions (GFs). A very popular class of methods is based on the solution of an integral equation for the GF containing an effective potential, the so-called self-energy, which needs to be approximated. The well-known GW approximation belongs to this class; this approximation is the method of choice for calculating band structures, but it also shows several shortcomings, such as the wrong description of satellites in photoemission spectra, in particular in so-called strongly-correlated materials. Therefore more refined levels of approximations are needed to keep the pace with the advances made in experiments.

Recently much progress has been made in this direction both by going beyond standard methods and also exploring completely novel routes to calculate GFs. The ETSF Correlation Team has been created precisely in this spirit. From the regular meetings of the Correlation Team it has become clear that a new wave of original ideas, understanding, and solutions has pervaded the field, and that it is timely to gather these new concepts in a workshop.

A CECAM workshop called “Green's functions methods: the next generation" will bring together experts and young promising scientists involved in the challenging new developments in the field June 4 to 7, 2013 in Toulouse, France.