Effective field theories

An effective field theory is a quantum field theory that is taken to describe the physical world in a limited range of length scales. While a fabled final theory of physics is supposed to describe the world down to arbitrarily small length scales, effective field theories provide a coarse-grained description of the behaviour of quantum fields and particles above some finite length scale. This way of thinking about quantum field theory models arose in the 1970s along with a framework called the renormalisation group. From this, and related techniques, a new methodology has arisen for constructing models of the behaviour of quantum particles at a particular physical scale.

Effective field theories have been connected to a number of epistemological and metaphysical debates in the philosophy of science. Some have seen the effective field theory concept as hostile to scientific realism, while others have attempted to use it to articulate and defend a form of scientific realism. Some have seen the relationship between effective field theories at different scales as exemplifying a form of emergence in physics, while others have argued that it falls under the purview of standard accounts of intertheoretic reduction. While little consensus has been reached on these questions it is, at least, agreed that the effective field theory ideology represents an important conceptual shift in the way that physicists think about scale which philosophers of science need to take into account.