### 1.3 Notation and conventions

Throughout the article we assume the “MTW” [80] conventions. We also generally assume
geometrized units , unless specifically noted otherwise. A coordinate basis will
always be used, with spacetime indices denoted by lowercase Greek letters that range over
(time being the zeroth coordinate), and purely spatial indices denoted by lowercase Latin
letters that range over . Unless otherwise noted, we assume the Einstein summation
convention.