Alexey Golovnev (Saint Petersburg State University)
New ideas in massive gravity
Massive gravity dates back to the classical paper of Fierz and Pauli in which it has been shown how to get rid off the sixth (ghost) polarisation of the massive graviton, at the linear level. However, for quite a long time it was widely believed that the Boulware-Deser ghost inevitably comes back with non-linear corrections. This obstacle was surmounted in 2010 at the price of introducing a square root of a matrix into the action which naturally entails certain existence and uniqueness issues. I will review modern theories of massive gravity and their problems, and also will give a new formulation of the model, directly in terms of elementary symmetric polynomials of eigenvalues instead of the matrices themselves. It turns out that the new construction has a wider range of applicability.