I'm currently an HQI postdoc at Harvard University.

[The following is what I wrote when I joined the site as a PhD student. Leaving it here as a time capsule :)] An unsolicited list of some of my favourite concepts in physics:

• Topological phases of matter
• Pretty much all incarnations of topology in physics
• Pretty much all topology
• Relation between entanglement and geometry
• Renormalization and effective theories (okay okay pretty standard stuff from a curriculum point of view, but so beautiful...)
• Anything John Baez has written about
• Most things Penrose has written about
• How scattering amplitudes in spacetime can be rewritten as holomorphic knot invariants in twistor space (!)
• Boltzmann's entropic reasoning
• Shape dynamics (coincides with GR in most ways but is conceptually more pleasing and also gives radical re-interpretations of black holes etc)
• Pilot-wave theory (it's mainly great for explicitly showing that quantum mechanics at least allows for a realistic interpretation, but I realize most people don't care; under-appreciated is the fact that it can be useful for semi-classical descriptions)
• ...