In the quest for a unified theory
Despite more than half a century of strenuous efforts, the integration of the force of gravity with the other three fundamental forces has not yet been achieved. The most promising approach has been that of string theory, in which all subatomic particles are represented as different states of mathematical 'strings' vibrating in an abstract space. String theory has given insights into early universe cosmology and models beyond the standard model of particle physics. It has also provided powerful tools for scientists in the UNIFY (Unification of fundamental forces and applications) project to study open problems in theoretical physics and interpret data from the Large Hadron Collider and gravitational waves detection experiments. The aim of the EU-funded project was to enhance knowledge exchange and establish collaborations among internationally recognised experts in Canada, Europe, Japan and the United States. Over its four-year lifetime, the UNIFY network also served as a training platform for young scientists commencing studies on the fundamental workings of nature. Three different lines of research were pursued. Although string theory provides an attractive route to quantum gravity, alternatives were explored towards conformal field theories. Researchers sought to create new links between quantum theory and gravity through the gauge/gravity duality. On the other hand, numerical approaches were adopted to describe cosmological singularities and the nature of dark matter. Importantly, UNIFY has been successful in reviving the bootstrap theory that was eclipsed by the success of the standard model. This theory is based on the idea that nature cannot be reduced to fundamental fields and the corresponding particles. On the contrary, it proposes the concept of particles as interconnections in an inseparable cosmic web, which arises in quantum theory and acquires its dynamic nature in relativity theory. All in all, UNIFY network's efforts have contributed significantly to enhancing our understanding of the physics of strong interaction as well as the physics behind unifying theories that include strong gravitational fields. However, the complete unification of all of physics will not be possible until the fundamental problems of quantum theory are resolved.
Keywords
General relativity, quantum theory, fundamental forces of nature, string theory, UNIFY, bootstrap theory