Online Classes During COVID-19 Period: A Study of Students’ Experience at Jamia Millia Islamia, New Delhi, India

Abstract

We investigate gravitational lensing in the strong deflection regime by loop quantum gravity (LQG)-motivated rotating black hole (LMRBH) metrics with an additional parameter l besides mass M and rotation a. The LMRBH spacetimes are regular everywhere, asymptotically encompassing the Kerr black hole as a particular case and, depending on the parameters, describe black holes with one horizon only (BH-I), black holes with an event horizon and a Cauchy horizon (BH-II), black holes with three horizons (BH-III), or black holes with no horizons (NH) spacetime. It turns out that as the LQG parameter l increases, the unstable photon orbit radius xps, the critical impact parameter ups, the deflection angle αD(θ) and angular position θ∞ also increases. Meanwhile, the angular separation s decreases, and relative magnitude rmag increases with increasing l for prograde motion but they show opposite behaviour for the retrograde motion. Using supermassive black holes (SMBH) Sgr A* and M87* as lenses, we compare the observable signatures of LMRBH with those of Kerr black holes. For Sgr A*, the angular position θ∞ is ∈ (16.404, 39.8044) µas, while for M87* ∈ (12.3246, 29.9057) µas. The angular separation s, for SMBHs Sgr A* and M87*, differs significantly, with values ranging ∈ (0.008306-0.37573) µas for Sgr A* and ∈ (0.00624-0.282295) µas for M87*. The deviations of the lensing observables ∆θ∞ and ∆s for LMRBH (a = 0.80, l = 2.0) from Kerr black holes can reach up to 10.22µas and 0.241332 µas for Sgr A*, and 7.68344 µas and 0.181317 µas for M87*. The relative magnitude rmag ∈ (0.04724, 1.53831). We estimate the time delay between the first and second relativistic images using twenty supermassive galactic centre black holes as lenses to find, for example, the time delay for Sgr A* and M87* can reach approximately 23.2562 min and 33,261.8 min, respectively. Our analysis concludes that, within the 1σ region, a significant portion of the BH-I and BH-II parameter space agrees with the EHT results of M87* and Sgr A*. The possibility of LRMBH being a BH-III with three horizons has been almost ruled out, except for a small portion of parameter space, by θ sh bounds of Sgr A* and M87* measured by EHT whereas NH without horizon is completely ruled out. We discover that the EHT results of Sgr A* place more stringent limits on the parameter space of LMRBH black holes than those established by the EHT results of M87*.

COVID-19 Vaccine Coverage in India: A District-Level Analysis

“…India is one of the few LMICs that produced COVID-19 vaccines domestically [ 23 ]. In the past decade, India has stood out as one of the largest vaccine producers in the world, with a share of around 60% of vaccine supplies to UNICEF [ 24 , 25 , 26 , 27 , 28 , 29 ]. The COVID-19 vaccination campaign in India has been one of the largest in the world [ 30 , 31 ].…”

Covid-19 Vaccination in India: An Exploratory Analysis

“…Among the LMICs, India is one of the few that produced covid vaccines domestically [20]. In the past decade, India has stood out to be one of the largest vaccine producers in the world with a share of around 60% of vaccine supplies to UNICEF [21,22,23,24,25,26]. Covid vaccination campaign in India was one of the largest in the world [27,28].…”