Classical Background Independence

Abstract

Abstract This chapter introduces the concepts of general covariance, diffeomorphism invariance, and background independence, and distinguishes between all three. It then proceeds to consider different possible definitions of background independence, with a particular focus on (a) the existence of certain kinds of ‘fixed’ fields in the formalism of a physical theory; (b) the presence of Andersonian ‘absolute objects’ in a theory; (c) definitions in terms of variational principles; and (d) definitions which involve appropriate ‘matching’ of geometrical and physical degrees of freedom in a theory. This chapter, therefore, develops the toolkit which will be used to assess the background independence of various physical theories in later chapters.