We construct wormholes in Einstein-vector–Gauss–Bonnet theory where a real massless vector field is coupled to the higher curvature Gauss–Bonnet invariant. We consider three coupling functions which depend on the square of the vector field. The respective domains of existence of wormholes possess as their boundaries (i) black holes, (ii) solutions with a singular throat, (iii) solutions with a degenerate throat and (iv) solutions with cusp singularities. Depending on the coupling function wormhole solutions can feature a single throat or an equator surrounded by a double throat. The wormhole solutions need a thin shell of matter at the throat, in order to be symmetrically continued into the second asymptotically flat region. These wormhole spacetimes allow for bound and unbound particle motion as well as light rings.

Germany

Simon Barton

Claus Kiefer

Burkhard Kleihaus

Jutta Kunz

Symmetric wormholes in Einstein-vector–Gauss–Bonnet theory

We extend recent discussions of singularity avoidance in quantum gravity from isotropic to anisotropic cosmological models. The investigation is done in the framework of quantum geometrodynamics (Wheeler–DeWitt equation). We formulate criteria of singularity avoidance for general Bianchi class A models and give explicit and detailed results for Bianchi I models with and without matter. The singularities in these cases are big bang and big rip. We find that the classical singularities can generally be avoided in these models.

Nick Kwidzinski

Dennis Piontek

Singularity avoidance in Bianchi I quantum cosmology

We show that the complex dynamics of the general Bianchi IX universe in the vicinity of the spacelike singularity can be approximated by a simplified system of equations. Our analysis is mainly based on numerical simulations. The properties of the solution space can be studied by using this simplified dynamics. Our results will be useful for the quantization of the general Bianchi IX model.

Poland

Włodzimierz Piechocki

On the dynamics of the general Bianchi IX spacetime near the singularity