Physics

Jonathan Bain (New York University)
Naturalness, as a guiding principle for effective field theories (EFTs), requires that there be no sensitive correlations between phenomena at low- and high-energy scales. This essay considers three reasons to adopt this principle. The first two are that it has been empirically successful, and that it is consistent with what Williams (2015) calls a "central dogma" of EFTs; namely, that phenomena at widely separated scales should decouple. I argue that these are not compelling reasons: The modest empirical success of naturalness must be balanced by spectacular empirical failures, and a distinction between two types of EFTs, Wilsonian and continuum, suggests that while decoupling may be a central dogma of EFTs, naturalness is not. On the other hand, a third reason to be natural is that it underwrites a non-trivial notion of emergence. Thus to the extent that one desires to interpret EFTs as describing emergent phenomena, one should be natural.

Samuel Fletcher (University of Minnesota, Twin Cities)
The concept of emergence, as it is implemented in modern physics, is commonly invoked but rarely defined; even when it is, it is typically only done so informally. Building on recent influential work by Butterfield (2011a,b), I provide precise formal definitions of emergence concepts as they pertain to properties represented in models, applying them to some basic examples from spacetime and thermostatistical physics. The chief formal innovation I employ, similarity structure, consists in a structured set of similarity relations amongst those models under analysis--and their properties--and is a generalization of topological structure.

Martin King (University of Bonn)
Six years after the 2012 discovery of the Higgs boson, there is still a large number and variety of viable models in particle physics that offer potential explanations of particle masses via electroweak symmetry breaking (EWSB). All of these are, to some degree, still active research avenues in particle physics. The Standard Model (SM) features the simplest implementation of the Higgs mechanism, which is a single doublet with one fundamental scalar particle. Other models treat the fundamental scalar as part of an extended Higgs sector, or have the symmetry breaking role played by a composite, rather than a fundamental, scalar. Though the SM is heavily favoured as the explanation of masses, philosophical accounts of explanation are unable to either accommodate it or it single out. This paper proposes an account that looks to theory in order to maintain a high threshold for explanation and distinguish between the SM Higgs mechanism and other models that are merely potential explanations of particle masses.
I argue that what makes the Higgs mechanism the best available explanation of particle masses is not its realistic representation of causes or structure, but its association with other models in an empirically broad and highly-confirmed scientific theory. A goal of the paper is to singularly pick out the SM explanation as the best available explanation, yet allow for changes in explanatory judgements among the relevant scientific community as that scientific theory is advanced, changed, eventually replaced. The SM Higgs mechanism is a part of the most highly-confirmed theory in particle physics and, I argue, we are therefore highly justified in claiming that it provides an explanatory account of particle masses. 

Elay Shech (Auburn University), Patrick McGivern (University of Wollongong)
We examine arguments for distinguishing between ontological and epistemological concepts of fundamentality, focusing in particular on the role that scale plays in these concepts. Using the fractional quantum Hall effect as a case study, we argue that we can draw a distinction between ontologically fundamental and non-fundamental theories without insisting that it is only the fundamental theories that 'get the ontology right': there are cases where non-fundamental theories involve distinct ontologies that better characterize real systems than fundamental ones do. In order to reconcile these distinct ontologies between fundamental and non-fundamental theories, we suggest that ontology must be understood as scale-dependent.

David Kinney (London School of Economics)
In this article, I consider Curie's Principle from the point of view of graphical causal models, and demonstrate that the usual adequacy conditions for causal graphs---i.e. the Causal Markov Condition and Minimality---do not require anything like Curie's Principle to be true. In light of this finding, I conclude that Curie's Principle is, at best, a useful heuristic for discovering causal structure, rather than a deep truth about the causal structure of nature itself.