# Physics of interacting spin-2 fields and its applications

Project leader

Funding source

Swedish Research Council - Vetenskapsrådet (VR) |

Project Details

Description

Elementary particles and the fields that mediate interactions between them are classified based on their "spin". At the fundamental level we encounter fields of spin 0, 1/2, 1 and 2. By now, we have consistent theories for fields of spin 0, 1/2 and 1 and these are the building blocks of the Standard Model of particle physics (SM). For spin 2, until recently we had a consistent theory only for a single massless spin 2 field. This is the gravitational field described by Einstein's theory of General Relativity (GR). By now there are indications, both theoretical and experimental, for new physics beyond SM and GR. Since many of these indications are related to gravitational physics, it is natural to consider extending the gravitational sector to address the new issues. But attempts to write a theory for two or more interacting spin-2 fields generically led to inconsistencies. Thus spin-2 physics becomes a challenging area in theoretical physics. We recall that a central activity in theoretical physics has been to construct consistent theories that can be used as building blocks in models of nature. Examples are the Dirac theory of electron, Higgs model and Yang-Mills theory, all first constructed as consistent theories at an abstract level. More recent examples are work on Supersymmetry and String Theory. The aim of the current project is to construct and study consistent theories of interacting spin 2 fields and investigate their physical implications. In this way, one obtains new, non-trivial but still natural, theoretical frameworks for exploring physics beyond General Relativity and the Standard Model. Only recently it has become possible to construct basic theories of interacting spin 2 fields, in large part due to our recent work in the field. Spin 2 fields of this type interact with gravity and change its behaviour, hence their presence in nature will have consequences for gravity and cosmology. The hope is that, if successfully implemented, some of the intractable puzzles associated with gravitational physics could be addressed more effectively in the framework of extended spin-2 theories.