Time：2:00pm（Special time 2pm）, Apr.21th (Thursday)

Zoom ID：898 2287 1525，密码：6360

Speaker：Prof. Philip Hopkins（California Institute of Technology）

Title：From Micro to Macro: Stars, Dust, Cosmic Rays, and how they Change the Universe

Abstract: The fundamental challenge in understanding galaxy and star formation, and the physics of the interstellar, circum and inter-galactic medium (ISM/CGM/IGM) lies in the fact that while gravity acts in a "top-down" fashion,  other "micro-physics" on scales as small as stellar interiors and below has effects which propagate "back up" to alter the Universe on cosmological scales. I'll give a brief review of some of the work our group has been doing in the last few years to bridge this tremendous range of scales in the context of star and galaxy formation, particularly with respect to the effects of "feedback" (jets, outflows, supernovae) from stars. I'll then discuss two specific examples -- interstellar cosmic rays and dust -- where fundamental uncertainties in "micro-physics" on sub-AU scales produce qualitatively different macroscopic behaviors of gas accretion, star formation, and outflows in star forming regions and galaxies. I'll review how new micro-physical instabilities and processes may change the "textbook" stories of these constituents of the ISM and resolve some long-standing puzzles, and how we might hope to make progress given the enormously disparate range of scales involved.

Brief CV：Prof. Philip Hopkins is a professor of theoretical astrophysics at Caltech, with research interests in the formation of galaxies, stars, planets, blackholes, astrophysical fluid dynamics, plasma physics, cosmology and dark matter. Prof. Hopkins obtained his PhD from Harvard in 2008, and moved to University of California Berkeley as a Miller and  Einstein Fellow from 2008 to 2013. Prof. Hopkins became an assistant professor at Caltech in 2013, and was promoted to full professor in 2017. Prof. Hopkins is a recipient of many awards, including the highly-prestigious American Astronomical Society Helen B. Warner Prize for Astronomy. Prof. Hopkins has published ~380 peer-reviewed papers (~120 lead-author) with total citations exceeding 33,700 (~16,000 lead-author) and an h-index of 96 (62 lead-author).

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