Talks

From quenched physical systems to simple optimization algorithms, descent in an energy or cost landscape is thought to underpin many interesting phenomena. Likewise, the geometry of this landscape is thought to explain diverse outcomes of this descent: in those with few minima, the lowest are easily found; while in those with very many, getting stuck among a proliferation of high minima is overwhelmingly likely. In mean-field spin glasses and inference problems, we can hope to use geometry to explain when transitions between these behaviors occur and which kind of minima will typically be found. I will describe the past success of this approach in the simplest spin glass models and its recent failure in slightly less simple ones. I will share several new results on the statistics and arrangement of metastable states and saddle points which together indicate that traditional mean-field geometric tools may not be able to answer everything. Finally, I share some thoughts on what extensions might be needed to precisely predict where descent goes.

In the current epoch of neutrino physics, many experiments are aiming for precision measurements of oscillation parameters. Thus, various new physics scenarios which alter the neutrino oscillation probabilities in matter deserve careful investigation. Recent results from NOvA and T2K show a slight tension on their reported values of the CP violating phase $\delta_{CP}$, which may hint towards the possible role of New Physics. The upcoming long-baseline experiments DUNE and T2HK not only perform precision neutrino measurements but also possibly unveil new interactions and symmetries beyond those predicted in the Standard Model. In this context, I will discuss the exploration of some of the popular beyond the Standard Model scenarios with the current and the upcoming neutrino oscillation experiments.

Strongly coupled confining theories are well-motivated in many BSM frameworks. The early universe cosmological history of these theories provides possibilities for observable signals. These theories undergo confinement deconfinement phase transition in the early universe, which can result in gravitational wave signals, observable in upcoming experiments. Using AdS/CFT, these theories have been studied in the Randall-Sundrum framework, and various quantitative aspects of the phase transition have been calculated. In the models that have been considered, the rate of transition from the deconfined phase to the confined phase is very small and leads to a period of supercooling. This enhances the gravitational wave signal, but presents a tension between a low confinement scale and fitting to the standard picture of BBN. In this talk, I will briefly review the calculations leading to these conclusions, and argue that some of the issues are specific to the simplified models that have been studied. I will present two modifications that are expected on general grounds, motivated by including strong IR effects systematically. Such effects change the results significantly. In particular, new qualitative features appear which have been missed in previous investigations. I will briefly comment on the phenomenological implications and open questions. The talk will be based on 2309.10090 and 2401.09633.

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Fueling and feedback couple supermassive black holes (SMBHs) to their host galaxies across many orders of magnitude in spatial and temporal scales, making this problem notoriously challenging to simulate. We use a multi-zone computational method based on the general relativistic magneto-hydrodynamic (GRMHD) code KHARMA that allows us to span 7 orders of magnitude in spatial scale, to simulate accretion onto a non-spinning SMBH from an external medium with Bondi radius ~ 2e5 G*M/c^2, where M is the SMBH mass. For the classic idealized Bondi problem, spherical gas accretion without magnetic fields, our simulation results agree very well with the general relativistic analytic solution. Meanwhile, when the accreting gas is magnetized, the SMBH magnetosphere becomes saturated with a strong magnetic field. The density profile varies as ~ r^(-1) rather than r^(-3/2) and the accretion rate is consequently suppressed by over 2 orders of magnitude below the Bondi rate. We find continuous energy feedback from the accretion flow to the external medium at a level of 1% of the accreted rest mass energy (~ 0.01 Mdot * c^2). Energy transport across these widely disparate scales occurs via turbulent convection triggered by magnetic field reconnection near the SMBH. Thus, strong magnetic fields that accumulate on horizon scales transform the flow dynamics far from the SMBH and naturally explain observed extremely low accretion rates compared to the Bondi rate, as well as at least part of the energy feedback.

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In this talk I will present an update on my work with Ben Gammage and Aaron Mazel-Gee on the 2-categories of boundary conditions in the A and B-twists. In particular I will explain how 2-categorical 3d mirror symmetry decategorifies to the Koszul duality of hypertoric categories O discovered by Braden-Licata-Proudfoot-Webster.

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