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Welcome! to my webpage, hosted by the Department of Physics & Astronomy at the University of Utah. I am a Professor, working in theoretical and computational astrophysics, with focus on planet formation, galactic dynamics, as well as some relativistic astrophysics. Here you will find information about my research, recent courses, and other things that I do at The U.
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Research
Highlights and animations
| Cosmic voids! Margaret Geller and I revisited the orbital dynamics of seemingly empty bubbles in the vast cosmic web of galaxies, galaxy clusters and superclusters. We explored a broad range of cosmological models to understand the motion of galaxies inside voids where the contribution from enigmatic dark energy is comparatively strong. This arxiv link leads to a description of our work. Also, please have a look at our animation, showing the evolution of structure within the cosmic web. | |
| Dust as a solar shield. Sameer Khan, Scott Kenyon, and I explored the potential of using dust clouds or streams for slightly dimming the sun from Earth's perspective. Our work demonstrates that large amounts dust, comparable to the output of open pit mines here on Earth, could temporarily reduce the amount of solar radiation by a percent or so. Please check out our PLOS Climate article and the wide range of responses to our work. | |
 | Origin of Pluto's moons. Our favorite binary planet, Pluto-Charon, has four moons -- Styx, Nix, Kerberos, and Hydra -- packed together on nearly perfect, "almost circular" orbits. Scott Kenyon and I have worked to understand how they formed. Please see our latest manuscript about Pluto-Charon, and this animated "drive-thru" of the PC system. | |
| Black holes and hypervelocity stars! Warren Brown, Margaret Geller, Scott Kenyon, and I study the origin of hypervelocity stars, which travel so fast that they are escaping our Galaxy. . Some may have started out as members of binary stars in the Galactic Center, and got flung out when they strayed too close to the Galaxy's supermassive black hole. What happens to the binary partner? Here's one idea.... | |
| Flyby! The Sun might have captured planets from a passing star. Animations that Scott Kenyon and I made (like THIS ONE!) show how this could happen. |
Teaching
| PHYS 3010 (lab) | Physics 4's Computer Lab (2023 [S=Spring]) |
| PHYS 3730+6720 | Intro to Computers in Physics (1998–2000 [F=Fall],2006 [F],2013 [F], 2014 [F], 2020 [S]) |
| ASTR/PHYS 7730 | Statistical and Computational Methods in Physics & Astronomy (2018 [S]) |
| ASTR 2500 | Foundations of Astronomy (2013 [F], 2014 [F[, 2015 [F[) |
| PHYS 1905 | Einstein in the 20th Century and Beyond (2005 [F], 2006 [F]) |
| MATH 6790 | Case Studies in Computational Engineering and Sciences (2002 [S) |
| PHYS 2220 | Physics for Scientists and Engineers II (Intro E&M; 2001–2013 [F,S]) |
| PHYS 6730 | Computational Physics I (1999–2001 [S]) |
Service
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Executive Committee (2018-present) | Physics & Astronomy |
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Associate Chair (2015-2016, 2019-present) | Physics & Astronomy |
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Chair (2016-2018) | Physics & Astronomy |
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Astronomy Task Force (2011–2014; 2018-present) | Utah Astronomy Group |
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Director of Graduate Studies
(2005–2007; 2010–2012) | Physics & Astronomy |
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Graduate Council (2011–2014) | The Graduate School |
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Undergraduate Council (2005–2006) | Office of Undergraduate Studies |
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Misc. Committees (1998–present) |
Admissions, Advising, Curriculum, ..., Policy Board, ... (Physics & Astronomy) |
| Referee/reviewer | Funding: DFG, NSF, NASA; Journals: Astrophys. J., Astron. J., MNRAS, A&A, Nature. |
