Talks

Compact objects like neutron stars and black holes host extreme conditions that cannot be replicated in terrestrial laboratories or even by the most ambitious future particle colliders. These conditions make them unparalleled natural laboratories for exploring new physics. Neutron stars stand out due to their incredibly strong electromagnetic fields, some of the most intense in the universe. This makes them ideal for testing the limits of electromagnetism and for probing physics beyond the Standard Model, including axions and dark photons, which are among the leading dark matter candidates. In this talk, I will highlight recent advancements in using pulsars to detect axions and discuss ongoing efforts to probe axions using magnetars, ultra-magnetic neutron stars that are the most magnetic objects in the Universe.

The calm of the quiescent sky is regularly interrupted by bursts of light that can outshine the entire galaxy. These powerful explosions are associated with mergers of compact objects, the collapse of stars, and rapidly accreting black holes, where gravitational binding energy is released and efficiently converted into radiation. The advent of electromagnetic time-domain surveys, high-energy telescopes, and gravitational-wave detectors is unveiling how matter works at these extreme conditions, offering insight into fundamental questions such as: How do compact objects form and acquire their magnetic fields? Which mechanisms launch outflows and jets? What determines the nature of the remnants they leave behind?  What are the main sites of heavy-element production?

The good books on GR agree on certain aspects of the theory that we could consider to be its “core” features. Beyond the core, however, we do not know exactly what GR should allow or not allow physically. For example, should we consider spacetimes with closed causal loops as part of physical GR or not? Are spacetimes with certain types of boundaries or singularities part of GR?  Most people expect that the answer to these sorts of questions will be answered by quantum gravity when we have it.  We can start to address them within different quantum gravity approaches even at their current partial state of their development. Within the framework of the path integral for quantum gravity and a Feynmanian heuristic for the recovery of the classical approximation, I will sketch out how answers may arise. I will use the example of causal set quantum gravity but I suggest that the ideas are applicable to other path integral approaches.