“Bulletin Board”

 School of Physics - September 1, 2022

Distinguishing a Slowly Accelerating Black Hole by Differential Time Delays of Images


 Dr. Mohammad B. Jahani Poshteh and Prof. Amjad Ashoorioon from the School of Physics of IPM along with their collaborator Prof. Robert B. Mann from the University of Waterloo, in a Physical Review Letter paper, proposed a method for determining the acceleration of black holes (BHs) by exploiting the fact that differential time delays associated with lensed images are substantially different with respect to the case of non-accelerating BHs. This small value of acceleration does not change the shadow of the BH significantly, nor does it change the angular positions of images in a lensing effect by the BH. Their results imply that it may be feasible to measure the acceleration of the supermassive BH at the center of the M87 galaxy. For such a small acceleration, it was assumed that a ray of light that is coming from a source behind the BH, for example, M87*, and is passing the BH, stays on or near the equatorial plane of the BH in the whole time during its travel.  Cosmic strings can break or fray to produce pairs of BH. These BHs will be accelerating due to the tension of the string. On the other hand, primordial BHs might have been produced in the early Universe. These BHs might get attached to the cosmic string. Then, they would be accelerating, too, due to the tension of the string. BHs connected to cosmic strings could evolve into supermassive BHs. However, if they are going to play a role in structure formation and be captured by galaxies, their velocity should be very small, which means that the acceleration should be small too.  Their results are published in  Journal: Phys.Rev.Lett. 129 (2022) 3, 031102   DOI: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.031102  
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