Prof. Arnold studies the theory of the strong, weak, and electromagnetic interactions at extremely high, relativistic temperatures, such as in the very early Universe (less than a millionth of a second after the Big Bang) or in relativistic collisions in heavy ion accelerators. Topics he has studied include investigating why there is significantly more matter than anti-matter in the Universe and understanding the properties of quark-gluon plasmas. The theoretical methods used for these very high energy problems (as much as a quadrillion degrees Kelvin) can also be applied to certain problems at very low temperatures (less than a millionth of a degree above absolute zero). In this vein, Prof. Arnold has also made some detours from his usual work on particle theory to study the transition temperature for Bose-Einstein condensation of dilute gases of extremely cold atoms.
For lay descriptions of some of Prof. Arnold’s research, click here (quark-gluon plasmas) and here (older work on the problem of matter/anti-matter asymmetry). For Prof. Arnold’s HEP-related publications,