# Is the idea of integrability the key to “what keeps the world together at its core”?

**String theories **are currently the preferred models throughout the world for clearing up one of the “last open questions” of fundamental physics: How can Einstein’s relativity theory be reconciled with quantum mechanics and the Standard Model of elementary particles? This unity can be attained through the strings; however, the exact definition of these theories remains mysterious. The question as to exactly what a string really is also remains unanswered. In order to gain a better understanding of the secret of strings it is perhaps a good idea to take a look at their movement in an idealized environment in contrast to the real world. A particularly symmetrically and mathematically suitable environment is based on the curved Anti-de-Sitter Space (AdS), which also plays an important role in cosmological models. Around ten years ago, the astounding assumption was proposed that in this case a dual description through a specific super-symmetrical particle model was possible. Could strings actually be, within the framework of this “AdS/CFT-Correspondence” as the duality is called, also particles and vice versa?

This particle theory, the “maximum super-symmetrical gauge theory”, is in turn an idealized version of exactly those theories that define the Standard Model of elementary particles which have been verified so successfully and with great precision. If there actually is a coherency with the strings this would open up manifold possibilities to make use of our extensive knowledge in particle physics to track down the strings. Conversely, we can also hope that, with the help of the strings, new research methods can be developed for the mathematically extremely difficult particle theories and, especially, for the theory of strong nuclear force. The reason: Despite great success in the computation of experimental consequences of the Standard Model, there are still many open questions that cannot be answered at all through the currently available mathematical methods.

**The “Bethe Ansatz” in string theory and particle physics - overseen symmetries**The discovery of Bethe’s integrable structures at this interface of strings and particles is thus an unexpected gift - and the conference at the Albert Einstein Institute has set itself the goal to use the consequences of the resulting new computing methods in an interdisciplinary manner. In particular, one can hope for, in the near future, constructive proof of the AdS/CFT- Correspondence with the already mentioned ramifications for our understanding of the fundamental interpretation of strings, as well as for the development of new quantitative methods for analyzing the theoretical components of the Standard Model of elementary particle physics. Moreover, it cannot be ruled out that the discovery of Bethe’s solvable structures in high-energy physics will also ultimately prove advantageous for solid state physics. Cause for hope in this respect is provided by the extremely subtle and attractive symmetries from the string and gauge theories, which had, to date, been overlooked in the sold-state theory.

**International cooperation**The topic that will be discussed at the conference at the AEI, is an outstanding example of excellent basic research in Europe: The innovative applicability of the “Bethe Ansatz” is being researched across all disciplinary boarders in European collaborative projects - these are leading the way all over the globe in this area. In addition to the Potsdam-based AEI, the formal and informal research networks include, among other institutions, the University Uppsala/Sweden, the ENS Paris/France, University Utrecht/Netherlands, Trinity College, Dublin/Ireland, the Universidad Autonoma in Madrid/Spain, the Niels Bohr Institute Copenhagen/Denmark and the University Krakow/Poland.

**Experts at the AEI**With Niklas Beisert and Matthias Staudacher, two internationally recognized experts for gauge and string theory are based at the AEI. Matthias Staudacher has just received, for his work in this area, the highly respected Academy Prize of the Berlin-Brandenburg Academy of Sciences and Humanities; in 2007, Niklas Beisert was awarded the prestigious Gribov Medal of the European Physical Society.