Talks

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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Information-theoretic insights have proven fruitful in many areas of quantum physics. But can the fundamental dynamics of quantum systems be derived from purely information-theoretic principles, without resorting to Hilbert space structures such as unitary evolution and self-adjoint observables? Here we provide a model where the dynamics originates from a condition of informational non-equilibrium, the deviation of the system’s state from a reference state associated to a field of identically prepared systems. Combining this idea with three basic information-theoretic principles, we derive a notion of energy that captures the main features of energy in quantum theory: it is observable, bounded from below, invariant under time-evolution, in one-to-one correspondence with the generator of the dynamics, and quantitatively related to the speed of state changes. Our results provide an information-theoretic reconstruction of the Mandelstam-Tamm bound on the speed of quantum evolutions, establishing a bridge between dynamical and information-theoretic notions.

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The mass and nature of neutrinos play an important role in theories beyond the standard model. The nuclear beta decay and double beta decay can provide the information on absolute effective mass of the neutrinos. At present, neutrinoless double beta decay (NDBD) is perhaps the only experiment that can tell us whether the neutrino is a Dirac or a Majorana particle. Given the significance of the NDBD, there is a widespread interest worldwide employing a variety of novel techniques. This talk will present a brief report of ongoing and proposed NDBD experiments and will highlight Indian efforts towards the feasibility study of search for NDBD in 124Sn.

I will first discuss how neutrino detectors such as SNO, SNO+, BOREXINO and MAJORANA Demonstrator can be repurposed to perform direct detection of dark matter in the Galactic halo via scattering and/or absorption. Then I will describe how "neutron shining through a wall" searches can be performed to smoke out dark sectors in neutrino facilities such as IsoDAR, COHERENT, SNS, and STEREO.