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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 show 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.

BIO

Prof. Jeremy Jin Leong Lim from University of Hongkong    :

1984: BSc. at Macquarie University, Sydney, NSW, Australia

1985: BSc. (Hons) at Macquarie University, Sydney, NSW, Australia

1991: PhD at Macquarie University, Sydney, NSW, Australia & CSIRO Division of Radiophysics & Australia Telescope National Facility

1991-1992: Postdoctoral Fellow, University of Maryland

1992-1994: Research Fellow, CalTech

1994-1995: Postdoctoral Fellow, ASIAA

1995-1996: Academia Sinica Fellow, ASIAA

1996-2000: Assistant Research Fellow, ASIAA

1999-2000: Adjunct Assistant Professor, NCU

2000-2009: Associate Research Fellow, ASIAA

2007-2009: Adjunct Associate Professor, NTU

2009: Research Fellow, ASIAA

2009-present: Associate Professor, University of Hong Kong

Research interest:

Radio Interferometry

Star Formation (Low-Mass, High-Mass, and Binary Systems)

Evolved Stars (Red Giants and Planetary Nebulae)

Active Galaxies (AGNs, QSOs, and Radio Galaxies)

Cosmology (Sunyaev-Zeldovich effect)

Host: Dandan Xu