School of Natural Sciences
A classic problem posed by long gamma ray bursts (GRB) is that the energy output requires gravitational energy release so deep within the host star that the prompt gamma rays should, upon naive consideration, have been obscured. It is suggested that photons emitted along the direction of the emitting plasma's motion are indeed geometrically blocked by optically thick baryonic matter, and that we usually see the photons that are emitted nearly backward in the frame of the emitting plasma. Many puzzling observations concerning GRB then fall into place.
We will discuss the notion of loops in linguistic structures, mainly in dictionaries. In a simplified view, a dictionary is a graph that links every word (vertex) to a set of alternative words (the definition) which in turn point to further descendants. Iterating through definitions, one may loop back to the original word. We will examine possible links between such definitional loops and the emergence of new concepts during the evolution of languages. Potential relation to living systems will be briefly discussed.
Our present framework for physics is difficult to modify without destroying its marvelous, successful properties. This provides a strong check on theoretical speculations and helps guide us to a small set of candidates for new laws. In this talk, Nima Arkani-Hamed, Professor in the School of Natural Sciences, illustrates these ideas in action by explaining why theoretical physicists knew the Higgs boson had to exist long before it was discovered at the Large Hadron Collider in July 2012. While the discovery of the Higgs is a triumph for both experimental and theoretical physics, its existence opens up a set of profound conceptual paradoxes, whose resolution is likely to involve radical new ideas. The talk concludes with a description of possible avenues of attack on these mysteries, and what we might learn from the LHC in this decade.