General Relativity for Pedestrians -- First 6 lectures

TL;DR

This paper provides an accessible overview of gravitational waves, discussing their flux, luminosity, black hole thermodynamics, and recent observational events, aimed at making complex concepts understandable for a broad audience.

Contribution

It offers a pedagogical introduction to gravitational wave physics, connecting recent discoveries with fundamental theoretical concepts and astrophysical phenomena.

Findings

GW luminosity can reach the Planck luminosity c^5/G.

GW event GW150914 is consistent with Hawking's area theorem.

Estimated GW amplitude from plasma bullets near V Hydrae.

Abstract

The 2017 Nobel Prize in physics awarded to Rainer Weiss, Barry C. Barish and Kip S. Thorne has generated unprecedented interest in gravitational waves (GWs). These notes are based on my lectures on various occasions - in the University of Delhi as well as in different GW schools held in India following the exciting direct detection of GWs. I discuss GW flux and luminosity while pointing out a curious aspect associated with the latter - physical dimensions of $c^5/G$ as well as third time derivative of mass quadrupole moment are that of luminosity. Formation of primordial black holes in the early universe and progenitors of fast radio bursts could have generated GW luminosity comparable to the Planck luminosity, $c^5/G$. I also address the issue of black hole thermodynamics in connection with the GW150914 event, demonstrating that this event is consistent with Hawking's black hole area theorem. In the last section, as an illustrative exercise, I estimate the GW amplitude expected from the fast moving plasma bullets that have been shot out from the vicinity of the carbon star V Hydrae, as reported recently by Sahai et al. (2016).