Sachin Venkatesh Thakku Saravana, Tchekhovskoy Group
"UNOfying the Scales: Simulating Black Hole Accretion from Event Horizon to Galaxy Scales using Physics-Informed Machine Learning"
Understanding black hole growth and evolution across vast spatio-temporal scales is crucial for modern astrophysics, yet current simulation methods face severe computational limitations. Among the many complexities in simulating accretion and feedback, accurately modeling the entire process in a way that obeys physical constraints, such as symmetries or conservation laws, remains a major challenge. Due to the enormous spatial and temporal range of scales, often spanning up to 9-12 orders of magnitude, even state-of-the-art GRMHD simulators become prohibitively time-consuming when used over time scales relevant to BH evolution. This work introduces a hybrid physics-informed machine learning framework to bridge the scale separations in such simulations by capturing both the small-scale physics near the black hole and the large-scale evolution while adhering to physical laws and constraints.
Dustin Greenwood, Shahriar Group
"Enhancing Sagnac Sensitivity via Superluminal Raman Lasing"
Precision rotation sensing is vital in many areas of both science and engineering from inertial navigation in spacecraft to measuring effects of General Relativity such as the geodetic and frame-dragging effect measured by Gravity Probe B. While high-precision mechanical gyroscopes have set the standard for decades, laser-based gyroscopes offer a robust, scalable alternative. Traditional Helium-Neon ring laser gyroscopes (RLGs) are fundamentally limited by their physical dimensions and the lock-in effect, which creates a deadband at the low rotation rates most relevant to relativistic measurements.
In this talk, I will discuss a new approach utilizing an intra-cavity medium of Rubidium vapor to engineer extreme anomalous dispersion via Raman transitions. By operating in the "superluminal" regime, where the group index approaches zero, we can enhance the Sagnac frequency shift by a factor proportional to the inverse of the group index, which can be very large. I will discuss the basics of the Sagnac effect, the implementation of this non-degenerate active lasing scheme and how it overcomes the limits of a passive cavity approach, and our current progress and difficulties in implementing this table-top sensor.