Our Gravity group lead by Tomi Koivisto investigates the general theory of relativity and its extensions. An aim is to develop a general-relativistic theory of quantum mechanics and particle physics, and the group also studies the possible cosmological implications of extended gravity theory.
This work is done in strong collaboration with researchers at the University of Tartu.
We have developed a gauge theory of gravitation and spacetime. The Standard Model of particle physics describes interactions in terms of the so called Yang-Mills gauge fields, the structure of the interactions being determined by the symmetry group of the Yang-Mills gauge theory. We have found that the emergence of spacetime and gravitational interaction therein can be described in the same framework, when taking the Lorentz group to define the fundamental symmetry of the gauge theory. The concept is illustrated in the following figure:
Some new ingredients of the theory with respect to some earlier theories of gravity are the realisation of spontaneous symmetry breaking and the chiral structure of spacetime. The Lorentz symmetry, or, in more rigorous terms Spin(4)=SU(2)xSU(2), implies the possible separation of interactions into left-handed and right-handed sectors, and the maximal separation for gravity is implied by the propagation of the observed gravitational waves. An analogous left-right asymmetry occurs for the weak interaction in particle
physics, which might be a hint towards the hypothetical unity of interactions, and towards the possible unification of the Higgs mechanism with the gravitational symmetry breaking. Pursuing this hint is one our current activities.
Besides the gauge approach to gravity theory, we have studied various different geometrical modifications and extensions of the general theory of relativity. New gravity models, new matter field models, and new models of coupling matter fields to gravity can result in dynamics that could explain dark energy, dark
matter or the hypothetical inflationary expansion of the very early Universe – and importantly, predict observational signatures that can be used to rule out, constrain or confirm the new models by their confrontation with the available precision data from the Solar system, astrophysical, cosmological, and gravitational wave experiments.
