Motivated by recent interest in the status and consequences of competition between the U.S. and China in A.I. research, we analyze 60 years of abstract data scraped from Scopus to explore and quantify trends in publications on A.I. topics from instit
utions affiliated with each country. We find the total volume of publications produced in both countries grows with a remarkable regularity over tens of years. While China initially experienced faster growth in publication volume than the U.S., growth slowed in China when it reached parity with the U.S. and the growth rates of both countries are now similar. We also see both countries undergo a seismic shift in topic choice around 1990, and connect this to an explosion of interest in neural network methods. Finally, we see evidence that between 2000 and 2010, Chinas topic choice tended to lag that of the U.S. but that in recent decades the topic portfolios have come into closer alignment.
Despite possessing a local spin $2$ moment on the iron site and a Curie-Weiss temperature of $45K$, the A site spinel FeSc$_2$S$_4$ does not magnetically order down to 50mK. Previous theoretical work by Chen and Balents advanced an explanation for th
is observation in the form of the $J_2$-$lambda$ model which places FeSc$_2$S$_4$ close to a quantum critical point on the disordered side of a quantum phase transition between a N{e}el ordered phase and a Spin-Orbital Liquid in which spins and orbitals are entangled, quenching the magnetization. We present new theoretical studies of the optical properties of the $J_2$-$lambda$ model, including a computation of the dispersion relation for the quasiparticle excitations and the form of the collective response to electric field. We argue that the latter directly probes a low energy excitation continuum characteristic of quantum criticality, and that our results reinforce the consistency of this model with experiment.
