~~~Title: Baryons, Dark Matter, and Light Scalars ~~~Abstract:The appearance of scalar fields with small masses is ubiquitous in physics beyond the Standard Model. In this talk I will describe how such light scalars can play important roles in cosmology, especially in connection to the origin of the baryons and dark matter of our universe. With regard to the baryons, I will show that a scalar with an approximate shift symmetry, such as the QCD axion, can naturally induce baryogenesis. For dark matter, I will present cosmological constraints on scalar dark matter obtained from analyses of the Lyman-alpha forest and the cosmic microwave background; here I will particularly focus on the ultralight regime and examine the long-standing claim that ultralight scalar dark matter may solve the small-scale issues of the CDM paradigm.
~~~ Slides: download