Within the perimeter of the Triangle de la Physique, theoreticians abound, whether they are grouped in several large theoretical physics laboratories well identified at the UPS (LPT, LPTMS), the CEA (IPhT) or the “Ecole Polytechnique” (CPhT), or immersed within larger units, working with experimentalists (LUMAT, LPS).

They develop both conceptual researches and novel numerical simulation methods, in more or less direct connection with the experiments. The considerable increase in computing power and the development of algorithmic tools have combined in order to make numerical simulation a branch of its own of research in physics.

A large number of theoreticians from the four large laboratories (LPT, LPTMS, CPhT, IPhT) are grouped in an informal statistical physics network of the south of the Paris region (PHYSTAT-Sud). The main goal of this structure is to set up a centre of excellence with greater visibility internationally than each of its components. A common monthly seminar has been held since 2006. Mention should be made of other initiatives grouping teams of theorists in the Triangle de la Physique. Bringing ETSF-France (LSI) closer to expert teams on materials with strong electronic correlations made possible the establishment of a centre of excellence with international stature in the field of electronic structure calculations ab initio. The synergies of such a centre with the experimental activities of the Plateau de Saclay (at the LPS, SOLEIL, and LLB for example) in the field of complex materials and nanomaterials are numerous. Another example is the network that was set up for structuring through regular organization of workshops on thematic issues, a numerical simulation activity developed with the Lumat federation by about forty researchers. The horizontal issues which were dealt with express common problems and the success of efforts for defining a standard for the local computing environment.

The international reputation of the Triangle de la Physique’s theoreticians has also led them to assuming a role of coordination in European structures. In particular, mention should be made of the Nanoquanta Network of Excellence, in which a team of theoreticians from the LSI (Polytechnique/CEA) make up the French component of a European Theoretical Spectroscopy Facility (ETSF), which might in the future associate all the relevant RTRA teams. Several other European networks of the RTN type also deserve mention.

Furthermore, statistical physics is known as being rich in interdisciplinary applications, ranging from physics of materials to finance and social sciences. Some of these activities, like the application of statistical physics concepts in algorithmic or in combinatorial optimization (error correcting codes, NP-complete problems), may form a point of common interest with Digiteo.

Finally, we cannot finish without mentioning the presence within the Triangle de la Physique of IDRIS (Institute for the Development of Research in Scientific Computer Science). This national centre of the CNRS, a coordinator of the European project DEISA (Distributed European Infrastructure for Supercomputing Applications) and member of HPC-Europa (Pan-European research infrastructure on High Performance Computing), actually makes available to researchers, on the basis of project tenders, advanced supercomputers, along with high quality training and support services. This is an essential asset for the theoreticians of the Triangle de la Physique.