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Astronomy Lunch Seminar Series

Astronomy Lunch Seminar Series

Davey 538

2025-09-23

Abstract: GRMHD simulations of accretion disks provide the bedrock for interpreting many modern observations of black hole accretion, especially direct radio imaging, which relies on large simulations libraries. Unfortunately, even with the most careful choices for initial conditions, simulations can retain an imprint of those biasing choices even at late times. Reconciling this intrinsic bias, which may not well represent actual astrophysical behavior, remains an outstanding and, I will argue, under-addressed theoretical problem. By making new, but not radically different choices in these initial conditions, I will demonstrate accretion disk simulations we have performed that represent a cost-saving approach to reaching long evolution timescales, and which demonstrate significant differences in comparison to the traditional approach. I will explain the fundamentals of our approach, a suite of new simulations of hot accretion flows in full 3D-GRMHD, and how these simulations may shift our interpretation of observations. In this library, we also explore the effect of high horizon-scale magnetization, but less than the Magnetically Arrested Disk (MAD) state.

TimeSpeakerTitle
12:00Mark AvaraSimulations of Black Hole Accretion: unusual behavior at the transition between SANE and MAD disks
About our wordmark
Monica The IGC wordmark was created by Monica Rincon Ramirez, while she was a graduate student at the Institute for Gravitation and the Cosmos (IGC). Monica enjoys drawing new connections between fundamental theory and observations. Her graduate work includes specialized topics in general relativity, loop quantum gravity, and quantum fields in cosmological backgrounds. In particular, her thesis work focused on finding effective quantum corrections to gravitational phenomena from spinfoams, and applications to cosmology. She received her PhD in 2024.

The wordmark symbolizes the scope and variety of research at the IGC. The base of the image represents quantum gravity, evoking the quantum geometrical picture from spinfoams and loop quantum gravity. These are among the approaches to fundamental questions studied at the Center for Fundamental Theory. The middle of the image represents the Center for Theoretical and Observational Cosmology by galaxies embedded in a smooth surface, characteristic of spacetime in general relativity and the much larger physical scales studied in cosmology. Finally, at the top, the surface curves to an extreme, representing a supermassive black hole accompanied by an energetic jet. These elements depict an active galactic nucleus, inspired by Centaurus A. Just to the right, a pair of black holes approaches merger. This top portion of the wordmark represents the Center for Multimessenger Astrophysics, which specializes in the study of high-energy phenomena in the universe.