John Barrow: Some Generalities About Generality

John D. Barrow - via commons

On 1 December 2014 I had the pleasure of attending a lecture by John David Barrow at the "Enriques" Department of Mathematics in Milano. Very kind person, when I approached him to be able to shake his hand and take a picture of him, he granted me both honors with great simplicity. Unfortunately that photo has now been lost among smartphone changes, perhaps kept in some hard disk stored somewhere, nor did I publish it on one of my social networks, but I still wanted to pay homage to it by offering you the abstract of an article from 2015, the fifth chapter of the book The Philosophy of Cosmology (arXiv):

We survey a variety of cosmological problems where the issue of generality has arisen. This is aimed at providing a wider context for many claims and deductions made when philosophers of science choose cosmological problems for investigation. We show how simple counting arguments can be used to characterise parts of the general solution of Einstein's equations when various matter fields are present and with different spatial topologies. Applications are described to the problem of singularities, static cosmological models, cosmic no hair theorems, the late-time isotropisation of cosmological models, and the number of parameters needed to describe a general astronomical universe.