Wednesday Colloquium


"Putting Infinity on the Grid"

David Hilditch (CENTRA, Technical University of Lisbon)

I will talk about an ongoing research program relying on a dual frame approach to treat numerically the field equations of GR (in generalized harmonic gauge) on compactified hyperboloidal slices. These slices terminate at future-null infinity, and the hope is to eventually extract gravitational waves from simulations there. The main obstacle to their use is the presence of ’infinities’ coming from the compactified coordinates, which have to somehow interact well with the assumption of asymptotic flatness so that we may arrive at regular equations for regular unknowns. I will present a new ’subtract the logs’ regularization strategy for a toy nonlinear wave equation that achieves this goal, and outline how this strategy can be applied to GR.


"Spectroscopic characterisation of very young systems in our Galaxy: from stellar clusters and young associations, down to sub-stellar objects."

Valentina D'Orazi (INAF - Astronomical Observatory of Padova, Italy)

Large spectroscopic surveys are (and will be ) providing us with a plethora of information on atmospheric parameters and detailed chemical composition (light, proton-capture, iron-peak and neutron-capture elements) in different populations across the Galactic components (bulge, thick disk and thin disc) for field and cluster stars. Interestingly, less attention has been devoted to the study of the chemical composition of very young stars (hereinafter stars younger than ~100 - 200 Myr). Two major issues are currently affecting our comprehension of these systems: the lack of young metal-rich stars/clusters in the solar surrounding and the so-called barium puzzle. I will review the status of the field and will present new results on both topics. General implications on Galactic chemical evolution and planet formation will be discussed. Finally, I will present SHARKs -a new facility with coronagraphic and spectroscopic capabilities that is under construction at INAF and will be mounted at LBT (Arizona, US) during Summer 2021. Scientific cases include exoplanet detection and characterisation, circumstellar discs and jets, AGN and solar system bodies.


"What was the last Nobel Prize in Physics given for?"

Marek Abramowicz (CAMK, Warsaw)