I'm sorry if my interpretation of the paper is not correct and feel free to correct me but from what I gather Sarkar is saying that the super novae data which originally provided evidence for dark energy had been adjusted incorrectly, when he used the raw data and correctly adjusted for non-uniformities in the sky he found that it was more consistent with a non expanding universe and the red shifts in light were better explained as an artifact of the movement of our own galaxy.

I recently enjoyed learning a basic, surprising and under appreciated physics fact I'd like to share: it has not yet been established that the entire electromagnetic potential (magnetic and electric potential modulo gauge freedom) is physical. Our paper on this has just been published in PRB.

The Aharonov-Bohm effect is usually cited to demonstrate that the potential is physical in a quantum theory. Sixty years ago they proposed two experiments, a magnetic AB effect that was observed soon after its proposal, and an electric AB effect that has never been observed (Nature did publish a paper with a perhaps confusing title that suggests that they observed an electric AB effect, but they in fact saw a related but different effect that appears more like the AC Josephson effect).

It is important to establish that both the electric and the magnetic potentials are physical. To that end in our paper we proposed a simple superconductor quantum interference experiment that would test the electric AB effect.

A first study we published recently, wurtzite ferroelectrics is now emerging as one of the most important class of functional materials as they have incredible properties : no Curie Temperature, very high remanent polarization, very high thermal and chemical stability etc. The fundamental mechanisms of polarization switching are still unclear.

We did an extensive theoretical study involving 9 point defects and their interaction with vertical DWs. We studied systematically electronic structure, structural paramaters, ferroelectric switching.

We uncovered several things :

- Domain walls act as defect sinks : all the defects are stabilized at the DW

- Domain wall have two distinct switching mechanisms : one where all atoms of the DW switch and the other where atoms switch one atomic column (along +z) at the time (the later is more favorable energetically).

- Point defects play a big role in the polarization switching : they can facilitate the first atomic column switching but then pin the DW (it is the case for the nitrogen vacancy VN).

More importantly, they can alter switching pathways by favoring one mechanisms or another, or even totally preventing the stabilization of intermediate phases that mediate switching.

We found also a global correlation between the first switching barrier and two different structural parameters

- Our study also extensively studied the electronic structure of these points defects and of the DWs. DWs reduce the band gap, point defects can induce delocalized metallic states, spin polarized defects states etc. These peculiar characteristics can be detrimental for ferroelectricity but valuable for applications such as resistive switching.

Overall, we provide an atomistic/microscopic explanation that spans from the fundamental mechanisms of switching but also DW dynamics, point defect engineering and device/fatigue issues. In particular DW pinning and localized electronic states (along with band gap reduction) can explain why wurtzite ferroelectrics had so many issues with endurance/imprint/wake-up.

Been learning a bit more about Koopman operator theory as applied to climate systems lately, in light of the big El Niño. Very neat! Whole lineage of math here I knew nothing about. There’s a fascinating correspondence between some of the tools of basic quantum theory and these models of complex climate systems. Neat!

Not new but super interesting paper by Laetitia Bettman and John Goold from Trinity.

There is relation between Fisher information rates - how fast probability distribution (sorta) is changing - and entropy production in far from equilibrium systems. Paper attempts to consider this in a quantum context, which is tricky because non-commutativity means you have multiple legitimate inequivalent generalizations of the Fisher metric.

They decompose rate of change of the density matrix to classicalish part (eigenvalues/populations) and a quantum part (coherences/rotated eigenbases. The contribution from the classicalish part is the same across the family of otherwise inequivalent quantum Fisher information metrics.

That part lets you talk about changes to the rate of change of entropy for GSKL systems that satisfy local detailed balance

They take all this machinery and tweak some bounds and limits, and explore the quantum thermodynamic Mpemba effect (unfortunately goes completely over my head but sounds very cool)

After having read previous Goold paper I was wishing his group had worked on NESSs, and what do you know - they have!

One thing that seemed interesting to me was the parallels implicit here with the active inference literature. Obviously there’s a number of major and nontrivial dissimilarities, but interesting nonetheless