Speaker: Andrew Coates (Tubingen U., IAAT)
Title: Prospects for testing two quantum gravity inspired deviations from general relativity
Abstract:
The first is a discussion of the potential observational signatures of the "area quantization" scenario. This comes from a proposal by Bekenstein and Mukhanov (separately) that the areas of black holes should be quantized. It was recently argued that this should lead to a largely reflective horizon and thus to graviational wave echoes (among other effects). In a recent PRL we argued that, for astrophysical black holes, the proposed reflectivity should be extremely weak (if it were to exist at all). I will also briefly discuss an ongoing project to strengthen this result. The second is based on the fact that efeffective field theory (EFT) considerations and direct quantum gravity considerations lead generically to violations of the weak equivalence principle (WEP). Of course, giving up the WEP introduces a huge number of possible couplings and an essentially intractable problem outside of vacuum (how would one go from a WEP violating extension of the standard model + whatever gravity sector to an equation of state for neutron stars for example?). There is also the further information that we know the WEP is valid to extreme precision in the solar system, so any such effort seems to be a waste.I will explain how, with a toy model, we have demonstrated that the WEP in strong gravity is not guaranteed by solar system experiments and also that the effects can be large in strong gravity, even with small WEP violating parameters. I will then go on to discuss ongoing work and the general future direction I see for this project.
Room: Zoom videoconference (contact justin.feng@tecnico.ulisboa.pt for URL)