Research interests
My research is focused on strongly-interacting systems with unusual transport properties. An example from particle physics is the quark-gluon plasma, the hot soup of quarks an gluons that existed micro-seconds after the Big Bang, and is reproduced. The quark-gluon plasma has a shear viscosity lower than any other known fluid. An example from condensed matter physics are the ``strange metal’’ states of heavy fermion compounds and high-temperature superconductors. These materials have an electrical resistivity scaling as the square of temperature, unlike the linear scaling of most metals. Few reliable techniques exist to study such systems. As a result, the origins of their unusual properties remain mysterious.
To study such systems, I use a novel technique, discovered in string theory, called holography. Holography is the statement that certain strongly-interacting systems are equivalent, in a precise mathematical sense, to Einstein’s theory of gravity in one higher dimension. In other words, by calculating things in Einstein’s theory of gravity, we can learn about the quark-gluon plasma, strange metals, and more!
To be clear, the systems involved in holography are purely theoretical, and do not describe any particular real system. However, they have the potential to reveal general principles applicable to real systems. In other words, holography provides “toy models” that may reveal patterns characteristic of strongly-interacting systems. Indeed, holography already has a success story: all fluids described by holography have the same ratio of shear viscosity to entropy density, of roughly 0.1. That value is shockingly close to the value estimated for the quark-gluon plasma, which is also roughly 0.1. Holography thus revealed a general principle: a ratio of shear viscosity to entropy density of roughly 0.1 is characteristic of strongly-interacting fluids.
The goal of my research is to find similar ``universal’’ properties. Indeed, with various collaborators I have discovered substantial evidence for generic, if not completely universal, properties of the electrical resistivity, impurity physics, entanglement, and more in many holographic systems. Above all, I have learned that holography and string theory have much to teach us about strongly-interacting systems!
2016-20 Module Coordinator for Final Year Synoptic Physics PHYS3017 and PHYS6015
2021 Module Coordinator for Linear Algebra for Physics PHYS1203
