The first direct detections of gravitational waves have had a strong impact on attempts to extend GR in the cosmological regime. In particular, GW170817 effectively ruled out some significant chunks of the modified gravity model space. I’ll summarise what the theoretical options for extensions of GR are, and what we’ve learnt about them from gravitational waves so far. I’ll also talk briefly...
Both observations and deeply theoretical considerations indicate that general relativity, our elegant standard model of gravity, requires modifications at high curvatures scales. Candidate theories of quantum gravity, in their low-energy limit, typically predict couplings to additional fields or extensions that involve higher curvature terms.
At the same time, the breakthrough discovery of...
Since the first detections of gravitational waves (GW) from merging binary black holes (BH), there has been a renewed interest in the possibility that at least some of these BHs could be primordial in origin. I will briefly discuss motivations for such primordial black holes (PBHs), formed from the collapse of large over-densities in the early Universe. I will then examine the on-going debate...
We will briefly review how supermassive black holes (SMBH) are modelled in galactic-scale simulations. Recently, large-scale cosmological simulations have been used to predict the gravitational wave background. These simulations typically rely on semi-analytic models to describe the small-scale black hole binary dynamics and gravitational wave emission, as these processes cannot be directly...
Our best estimate of the Universe's current expansion rate (the Hubble constant) from the local Universe (via the Cepheid distance ladder) is in four-sigma tension with the value extrapolated from cosmic microwave background data assuming the standard cosmology. Whether this discrepancy represents physics beyond the Standard Model or deficiencies in our understanding of the data is the subject...
I will give an overview on gravitational waves from phase transitions, and then focus on specific hidden sector scenarios such as dark photons or axions, and discuss how they could be probed by future gravitational wave observations in pulsar timing arrays, space and ground based detectors.
In this talk I will discuss experimental probes of dark compact objects in the new era of gravitational wave astrophysics. Such proposed objects include scalar (boson) stars, Q-balls, and dark matter clumps inside neutron stars. I will review the properties that will help us distinguish them from astrophysical objects, and the resulting gravitational wave phenomenology. I will also discuss...
