Special Events

Stefano Lucat, Utrecht University
Cosmological singularities and bounce in Cartan-Einstein theory

I will discuss the dynamics of a collapsing (homogeneous and isotropic) universe, and show that torsion induced interactions can prevent the universe from reaching a singularity, but lead to a regular bounce. This dynamic can be understood as the formation of fermionic condensate(s), which lowers the energy density of the fermions effectively slowing down the gravitational collapse. Before a singularity is reached, in fact, the null energy condition gets violated, and the energy density of the fermionic field reaches zero. At this point all the initial energy has been converted in a negative pressure, which causes the universe to re-expand. This process is possible because the energy density lost by the fermionic field is simply converted in the more energetically favourable condensate state, and will eventually come back as the universe cools down and gets bigger. I will discuss both classical and semi-classical treatment of this problem.

Markus Kunesch, Queen Mary University of London
Investigating singularities with numerical relativity

Our recent numerical simulations demonstrated that in higher dimensions even asymptotically flat black holes can break and give rise to naked singularities. This shows that if cosmic censorship were to hold in our universe, it would be a special property of four dimensional spacetimes. I will describe these results and outline other applications of the same numerical relativity code to cosmology, astrophysics, and AdS/CFT.