# Unravelling the ‘superstring’

EU-funded scientists made important advances in understanding and applying concepts relevant to string theory, purported by many to be the ‘long-sought ‘theory of everything’. Such complex mathematics is slowly unravelling the secrets of the Universe.

Many prominent theoretical physicists support the potential of string theory to explain the fundamental nature of the Universe. General relativity has yielded a wealth of information about the orbit of planets, the evolution of stars, the Big Bang and even black holes. However, the Theory of General Relativity only applies when quantum mechanics is ignored, basically at astronomical distances. Conversely, the relativistic quantum field theory only works when gravity is so weak that it can be ignored. String theory can be thought of as a theory of quantum gravity, seen by many to unite the Theory of General Relativity with quantum physics. In string theory, the fundamental particles of the Universe are not points but tiny one-dimensional (1D) loops behaving like vibrating, oscillating strings. The average size of a string, if it exists, is incredibly small. Thus, scientists must often use theoretical methods rather than experimental ones to study the concepts of string theory and test them. European scientists supported by funding of the ‘Covariant quantization of the superstring’ (Puresp) project sought to study string propagation in so-called Ramond-Ramond (RR) fields in the 10D space-time of type II superstring theory.String quantisation, assigning quantum states to the string itself, related to string propagation in RR fields was poorly solved until recently. Although a formal description now exists, many questions still remain regarding the solution and its applications. Scientists evaluated and disproved a conjecture related to the form of RR couplings relevant to applications such as computation of corrections to the entropy of black holes. Researchers also studied so-called holographic correspondence for RR-related spaces resulting in calculation of transport properties (viscosity) of very high temperature plasma with remarkable agreement to the viscosity of real quantum plasma produced by heavy ion collisions. EU-funded scientists thus made important advances in understanding quantisation of superstring propagation in background fluxes for RR fields with potential applications to black holes and other astrophysical concepts.