Some Highlights from The Week

Nov 14

In popular media

Natalie Wolchove wrote an interesting and contemporary take on the process of theoretical physics in Quanta Magazine. In it she explores two distinct attempts to understand the framework behind quantum field theory: entanglement entropy and the Amplituhedron. It's a peak behind the scenes of a field that's been struggling to advance in recent years.

Los Alamos National Lab published a neat article on their website about some work studying extreme lightning events.

Finally, I just cracked open cosmologist Katie Mack’s new book, “The End of Everything (Astrophysically Speaking).” And I’m immediately impressed. Her use of Robert Frost’s Fire and Ice was an outstanding, textured introduction to the mathematical forecasts for the late time behavior - and possible end - of the universe.

On the arXiv

Geometrizing TTbar by Per Kraus and friends.

I’ve been looking for a way into this TTbar deformation business, and having read a lot of Per’s work in the past, I figured it was a reasonable place to start. The local structure of TTbar theories isn’t clear, which makes the AdS/CFT correspondence a pretty natural - if naive - framework to study it. The authors reframe the construction in terms of AdS3/CFT2, which gives you the full power behind two-dimensional conformal field theory to play with. It looks like they’re limited in scope here to observables that remain fixed on the boundary, so it’s not clear what exactly we’re learning here. Much more to read, for sure.

A New Spin on the Weak Gravity Conjecture by Gary Shiu and friends.

The Weak Gravity Conjecture (WGC) basically amounts to demanding that gravity is always the weakest force, no matter what. When scaling to really small distance scales - where the gravitational coupling likely starts to grow - you could imagine a cross over effect or some other such weirdness on the renormalization group flows. The WGC is a principle the demands that not happen (for various, motivated reasons), and we can then turn that conjecture into a constraint and see if that helps us get a better handle on what the physics might do.

An important result from this is the implication that extremal, charged black holes can actually decay unless there is some additional symmetry protecting against higher dimensional operators in the UV. Of course, rotating black holes also have a notion of “extremality”, which is supposed to prevent decay at tree level. Gary and friends dug into the study of rotating black holes (particularly in the BTZ case… hello again AdS_3!), and related the WGC to the c-theorem associated to the boundary CFT, essentially proving it. Which is kind of neat! Surely, surely there is a story to the associated Kerr/CFT studies here.

The VERY NEXT DAY, this popped up: