Abstract:
Dark Matter (DM) is the clearest sign that the Standard Model of particle physics is incomplete. A determination of the DM particle mass will rule out entire classes of hypothetical extensions to the Standard Model, thus pointing the correct path towards New Physics. In this talk, I describe how gravitational lensing can differentiate between the two top contenders for DM: ultra-massive (WIMPs) versus ultra-light (Axion or Axion-like) particles, both hypothesized in different theoretical extensions to the Standard Model. Specifically, I focus on how DM in the form of ultra-light particles (mass ~10-22 eV) can resolve a two-decade old problem in
gravitational lensing, whereby galaxy DM models based on ultra-massive particles leave discrepancies between the predicted and observed properties of multiply-lensed images. The increasing success of ultra-light DM particles in explaining astronomical observations, naturally predicting cores in dwarf galaxies and a suppression of low-mass halos thus resolving the missing satellite problem, together with observational evidence for solitonic cores in galaxies, is starting to tilt the scale to new physics involving ultra-light particles.
Biography:
Amruth Alfred, originally from the island of Sri Lanka, is a URC Postdoctoral Fellow at the University of Hong Kong. Amruth is the recipient of the 2023 Hong Kong Young Scientist Award which is given annually to the best PhD research in Hong Kong within Physics, Chemistry and Mathematics, along with the 2023 IAU PhD Prize Honorable Mention which is given to the most remarkable PhD theses of the year. His research focuses on uncovering the nature of Dark Matter (DM), a mysterious substance that comprises a staggering 85% of mass in our Universe, through the technique of Gravitational Lensing - the phenomenon of how mass bends light as predicted by Einstein's General Relativity. By providing a credible explanation for resolving the two-decade long lensing anomaly problem that has plagued the community, Amruth's research has provided a new avenue to test the potential for ultralight particles, as opposed to ultramassive particles, to be a promising candidate for DM. This work was featured on the front cover for the June 2023 issue of Nature Astronomy, and has been rated as within the top 1% among all research articles across all journals for online attention.
Alternative online link： https://meeting.tencent.com/dm/u5gHxD1ObpKA ID：168853960