Physics

How big can a star get? Why would a star only pretend to explode? Can you hide one star inside another?

Take a tour of some of the strangest stellar phenomena in the universe during this talk featuring Emily Levesque. From the biggest, brightest, and most volatile stars to the explosive fireworks of core-collapse supernovae and the fascinating physics of gravitational waves, "weird" stars serve as a common thread for exploring our universe's history, evolution, and extremes. Levesque will discuss the history of stellar astronomy, present-day observing techniques, and exciting new discoveries, and explore some of the most puzzling and bizarre objects being studied by astronomers today.

Red supergiants (RSGs) are the helium-fusing evolved descendants of moderately massive (10-25Mo) stars, the result of a near-horizontal evolution across the top of the Hertzsprung-Russell diagram following their time on the main sequence. As the coldest and largest (in physical size) members of the massive star population, these stars represent a significant evolutionary extreme and serve as ideal "magnifying glasses" for scrutinizing our current understanding of massive stars and their role in the universe. RSGs are significant dust producers in young stellar populations, the observationally-confirmed progenitors of core-collapse supernovae, and a crucial step in the formation and population statistics of massive interacting binaries (including those that will ultimately produce compact object binaries and gravitational waves). Observations of RSGs can also be used to test stellar evolution and population models and as metallicity indicators in nearby galaxies. This talk will provide an overview of our field's knowledge of RSGs, identify some of the most pressing current questions about these stars, and consider the importance of RSGs in the coming decade as the next generation of observatories - including JWST, WFIRST, and the ELTs - comes online.

The study of black holes has revealed a deep connection between quantum information and spacetime geometry. Its origin must lie in a quantum theory of gravity, so it offers a valuable hint in our search for a unified theory. Precise formulations of this relation recently led to new insights in Quantum Field Theory, some of which have been rigorously proven. An important example is our discovery of the first universal lower bound on the local energy density. The energy near a point can be negative, but it is bounded below by a quantity related to the information flowing past the point.

One of the most enduring mysteries in particle physics is the nature of the non-baryonic dark matter that makes up 85% of the matter in the universe. For several decades, most searches for this mysterious substance have focused on Weakly Interacting Massive Particles (WIMPs). Recently, there has been a surge in theoretical interest in ultra-light-field dark matter candidates, including QCD axions (spin 0 bosons) and hidden photons (spin 1 bosons), which can be probed through their coupling to electromagnetism or nuclear spin. I will discuss general principles of efficiently searching for the direct detection of the electromagnetic coupling of these candidates, how the sensitivity of these experiments can be improved by the exploitation of quantum correlations in the electromagnetic signals that they produce, and describe the Dark Matter Radio, and experiment searching for axions and hidden photons in the frequency range of 1 kHz through 100 MHz.