Brief science items - September 2026 edition

Several science items of interest from recent weeks.  As always, apologies for missing some, which I'm sure to have done.

• A month ago, Premi Chandra, Piers Coleman, and Clare Yu published a really nice memorial biography of Phil Anderson, one of the great scientists and characters of 20th century physics.
• A few days ago Dam Son, an outstanding condensed matter theorist at U Chicago, posted a paper on his site that resolves a math issue that had been lingering related to a well-known paper from back in the heyday of anyon superconductivity.  The authors had always been afraid that their approach accidentally violated a sum rule.  It turns out, the authors had just misplaced a factor of 1/2, and their approach was actually exactly right.  The really novel bit here is that the paper is written as if it is single-authored by Claude, and acknowledges Dr. Son for prompts that led to the result.  See here for an interesting twitter thread on this via Sankar Das Sarma.  
• Tangentially related, Anthropic and Matt von Hippel achieved a new result, a 9-loop perturbation theory calculation based on N=4 super Yang-Mills theory.  These kinds of mathematically virtuosic calculations are exactly the sort of task that AI tools to which are extremely well suited now.  
• Three weeks ago, a neat paper appeared in Science Advances.  These folks used quantum interference of a Bose-Einstein condensate to test the equivalence principle in a quantum system.  The basic idea is, you take an ultracold atomic gas in a well-defined quantum state.  You split it and toss one component of it upward, while you hold the other component of it fixed in the lab frame. (This work is a descendent of this approach, which was happening in the lab above mine in back when I was in grad school.) The upward-thrown component accumulates quantum phase as it rises in the lab gravitational field, slows to a stop, and comes back down.  There is a specific amount of phase difference between the two components predicted by the equivalence principle (which says that inertial mass and gravitational mass should be exactly the same), and that's what the authors find.
• A couple of weeks ago, this paper appeared (shoutout to the first author, who is a Rice undergrad alum).   The authors fabricated a nanomechanical resonator made out of LiNbO3 and coupled it to a qubit to act as a measurement device.  Remarkably, through the qubit they are able to see transitions between individual vibrational quantum numbers in this many-atom mechanical resonator.  This is quite impressive, and it opens up many possibilities for transduction between different quantum degrees of freedom.  

More soon.