Concepts of Emergence Appropriate for Effective Field Theories

Abstract

This talk considers the extent to which the intertheoretic relation between an EFT and its (possibly hypothetical) high-energy theory supports a notion of emergence. When a high-energy theory exists, this relation is based on a process that involves the elimination of high-energy degrees of freedom. This elimination results in an EFT that formally bears little resemblance to the high-energy theory. I investigate the extent to which this lack of formal resemblance underwrites notions of novelty and autonomy that may be appropriately associated with emergence. I'll begin by reviewing the method by which an EFT is constructed from a high-energy theory by means of integrating out high-energy degrees of freedom from the latter. I'll then review a number of attempts in the philosophical literature to explicate the notion of emergence. I'll first consider general phillosophical accounts that identify emergence as supervienience without reduction, or as associated with various notions of autonomy (reductive, predictive, causal, and/or explanatory). I'll then consider more specific accounts related to physics in particular, including Batterman's (2002) notion of the failure of a limiting relation, and Mainwood's (2006)description of the concept of emergence associated with the claims of condensed matter physicists (e.g., Anderson 1972). This account conceives emergence as microphysicalism (the claim that emergent properties/entities are ultimately composed of microphysical properties/entities) coupled with novelty cashed out in terms of a mechanism (in this case spontaneous symmetry breaking) that produces a reduced phase space supporting (emergent) properties that are not explicitly defined on the initial phase space. A similar account is given by Wilson (2010), who explicates novelty in terms of an elimination of degrees of freedom. I'll suggest that Batterman's account does not quite succeed in the context of EFTs (simply put, the relation between an EFT and its high-energy theory cannot be described in terms of the failure of a limiting relation), and while the elimination of degrees of freedom does occur in EFTs, this process is different from the process described by Mainwood and Wilson (in particular, the phase space of an EFT is not, in general, a reduced phase space of a high-energy theory). This suggests that a notion of emergence as microphysicalism coupled with novelty can be applicable to the EFT context, as long as an appropriate mechanism that underwrites novelty, other than spontaneous symmetry breaking, can be identified. This mechanism perhaps can be identified simply as the particular approximation scheme employed in the construction of an EFT.