Seminars

Astrophysical jets associated with supermassive black holes (BHs) are believed to derive their power from the rotational energy of the BH itself, akin to how the Crab Nebula is powered by its pulsar. The Blandford-Znajek (BZ) mechanism, an electromagnetic Penrose process, provides a framework for understanding the physics of jet energetics. Specifically, it predicts the jet efficiency—the ratio of outflowing jet power to inflowing accretion power—to scale quadratically with the magnetic flux at and angular velocity of the black hole horizon. For rapidly spinning Kerr BHs, numerical simulations reveal jet efficiencies exceeding unity, a clear indicator of energy extraction from the black hole. At moderate spins, confirmation of energy extraction relies on the alignment of measured jet efficiencies with the BZ prediction. Over the past decade, this prediction has been validated across Kerr BHs with varying spin values. We present new findings from a large suite of magnetohydrodynamics accretion simulations conducted in spinning non-Kerr spacetimes, demonstrating that the BZ mechanism operates universally, extending its applicability to arbitrary BHs.

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TBA

Advancements and upgradations of particle colliders and accelerators made it possible to study the heavy hadrons and tetraquarks. For example the LHCb Collaboration discovered the doubly charm tetraquark (T_cc) in the year 2022, and it also observed the B_s -> K semi leptonic decay in 2021. In this situation it has become important to study these processes on lattice. In our previous works we studied the spectrum of singly, doubly and triply heavy bottom hadron and doubly heavy tetraquark using NRQCD for bottom and HISQ for up/down, strange and charm quark. We also studied the form factors of B_s -> K semileptonic decay. We faced some issues while carrying out those studies and I will discuss how we addressed them.

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