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【DoA Colloquium】February 18th by Bohua Li
Description
Title: New cosmological probes of ultralight dark matter
Speaker: Bohua Li
Abstract:
Ultralight scalar field dark matter (SFDM) has become one of the most studied dark matter candidates over the last decade. As a viable alternative to cold dark matter (CDM), ultralight SFDM mimics CDM on large scales, while resolving some of the small-scale challenges to the CDM model potentially due to its quantum nature. The propotypical ultralight SFDM—ultralight axions—described by a free real scalar field has been subject to various observational tests and the Lyman-alpha forest data provide the strongest constraint so far. In this talk, I will present several new cosmological probes of ultralight SFDM and an extended ultralight SFDM model described by a complex scalar field. Ultralight SFDM delays the formation of first dwarf halos and thus affects the 21cm signal from the Cosmic Dawn and the Epoch of Reionization. A possible early kination phase from the scalar field dynamics can amplify the primordial gravitational-wave background and explain the recent pulsar timing array results. Finally, I will show that the complex SFDM model acquires two novel elements compared with ultralight axions: the imperfect-fluid nature and the Noether current associated with the U(1) symmetry. I will discuss their dynamical implications for large-scale structure of the universe.
Bio: Dr. Bohua Li is an assistant professor at Guangxi Univerity. He received his PhD from the University of Texas at Austin in 2017. He was then a postdoc fellow at Tsinghua University under the International Postdoctoral Exchange Fellowship Program, before joining Guangxi University in 2021. His research interests focus primarily on the nature of dark matter, its theoretical predictions and observatonal tests.
Time: 14:00-15:00, 18/February, Tuesday
Venue: Room 506 (Large seminar room), Department of Astronomy
