To address these fundamental problems of current high-energy physics, many new ideas have been put forward; among the best developed ones are supersymmetry, extra dimensions, and string theory. Physicists at Nordita are actively participating in this research, in particular supersymmetry and string theory.
String theory asserts that elementary particles have an internal structure: Each particle is a string curled into a ring of a very small size. Different particles are just different vibrations of this string. These very simple assumptions have far-reaching consequences. Perhaps the most remarkable feature of string theory is its relationship to quantum gravity: In contrast to the Standard Model, string theory is capable of explaining all known particles and all types of interactions, including gravity. String theory has also proved to be mathematically very rich, and in the last decade has given rise to a whole new area of research, known as holographic duality.