image of M82 Starburst galaxy courtesy of Hubble
Dark matter & AXIONS
What is the dark matter? This is one of the biggest questions in physics. It turns out that most of the matter in the Universe isn't the every day stuff that Earth is made of. Rather, the amount of matter that we can count based on collecting light in telescopes does not match with our calculations of how much should be there. As a result, we believe that there is something called the dark matter making up the majority of matter -- over 80% -- in the universe.
Over the years, theoretical physicists have suggested many candidates for the dark matter. One such candidate is the hypothetical axion, which is a particle that helps to resolve a completely separate problem in particle physics. This is one reason the axion is such a great candidate: it's a twofer!
Most recently, my research into the axion has focused on whether it forms an exotic matter phase called a Bose-Einstein condensate, where a large number of axions would act as if they were one particle, like a hive mind. Whether axions form this matter state or not could have implications for how galaxies and ultimately every structure in the universe was formed.
Why is the universe so big but essentially the same everywhere? This important question is likely addressed by a phenomenon called inflation where, when the universe was just a fraction of a second old, spacetime expanded faster than the speed of light. This does not violate the universal speed limit because that limit only applies to the contents of spacetime, not spacetime itself. Although we have a general understanding of inflation, the exact nature of the equations that describe it remain elusive. Further, we don't know much about what happened immediately afterward. This time period immediately after inflation is known as reheating, and some of my work focuses on models of this era.
The Edge of Quantum Field Theory
Quantum Field Theory (QFT) is the mathematical framework that we use to describe all of particle physics. It evolved as the intersection of Einstein's special relativity, which describes matter when it is moving very fast, and quantum mechanics, which describes matter at microscopic scales. Together they describe particles, which are small and often moving fast. There is still much we don't understand about how to do QFT calculations, especially when we add in the wrinkle that spacetime is not always as it is described in special relativity, flat. Sometimes it is curved, and this leads to fun new phenomena, like the fact that it's not possible to define a region of space that has no particles. One of my areas of interest is helping to push the boundaries of what we can calculate.