'Emergence and Mechanism in the
Fractional Quantum Hall Effect' For
some authors, an adequate notion of emergence
must include an account of a mechanism by means
of which emergent behavior is realized.This
appeal to mechanism is problematic in the case
of the fractional
quantum Hall effect (FQHE)There
is a consensus among physicists that the FQHE
exhibits emergent phenomena, but there are at
least four alternative explanations of the
latter that, arguably, appeal to ontologically
distinct mechanisms, both at the microphysics
level and at the level of general organizing
principles.In light of this underdetermination of
mechanism, one is faced with the following
options:(I)
deny that emergence is present in the FQHE; (II)
argue for the priority of one mechanistic
explanation over the others; or (III) temper the
desire for a mechanism-centric account of
emergence.I will argue that there are good reasons
to reject (I) and (II) and accept (III).In
particular, I will suggest that a law-centric
account of emergence does just fine in
explaining the emergent phenomena associated
with the FQHE.

2015.

'Pragmatists and
Purists on CPT Invariance in Relativistic
Quantum Field Theories' Greenberg (2002) claims that the
violation of CPT invariance in an interacting RQFT
entails the violation of Lorentz invariance.This
claim is surprising since standard proofs of the CPT theorem require more
assumptions than Lorentz invariance, and are
restricted to non-interacting, or at best,
unrealistic interacting theories.This
essay analyzes Greenberg's claim in the context of
the debate between pragmatist approaches to RQFTs,
which trade mathematical rigor for the ability to
derive predictions from realistic interacting
theories, and purist approaches, which trade the
ability to formulate realistic interacting
theories for mathematical rigor.

Research on
quantum gravity
(QG) has historically relied on appeals to
guiding principles.This
essay frames three such principles within the
context of the condensed matter approach to
QG.I
first identify two distinct versions of this
approach, and then consider the extent to
which the principles of asymptotic
safety, relative
locality, and holography
are supported by these versions.The
general hope is that a focus on distinct
versions of a single approach may provide
insight into the conceptual and foundational
significance of these principles.

2013e.

'Emergence in Effective Field
Theories'
This essay considers the extent to which a
concept of emergence can be associated with effective field
theories (EFTs). I suggest
that such a concept can be characterized by
microphysicalism and novelty underwritten by the
elimination of degrees of freedom from a
high-energy theory, and argue that this makes
emergence in EFTs distinct from other concepts
of emergence in physics that have appeared in
the recent philosophical literature.

2013d.

'CPT,
Spin and Statistics, and the Ontology of
Relativistic Quantum Field Theories' CPT invariance
and the spin-statistics
connection are
typically taken to be essential
properties in relativistic quantum
field theories (RQFTs), insofar as the CPT and
Spin-Statistics theorems entail that any state
characterized by an RQFT must possess these
properties. Moreover, in the physics
literature, they are typically taken to be
properties of particles. But there is a
Received View among philosophers that RQFTs cannot
fundamentally be about particles. This essay
considers what proofs of the CPT and
Spin-Statistics theorems suggest about the
ontology of RQFTs, and the extent to which this is
compatible with the Received View.

2013c.

The Emergence of
Spacetime in Condensed Matter Approaches to
Quantum Gravity' Condensed matter
approaches to quantum gravity suggest that
spacetime emerges in the low-energy sector of a
fundamental condensate.This
essay investigates what could be meant by this
claim.In particular,
I offer an account of low-energy emergence that is
appropriate to effective field theories in
general, and consider the extent to which it
underwrites claims about the emergence of
spacetime in effective field theories of condensed
matter systems of the type that are relevant to
quantum gravity.

2013b.

'Category-Theoretic
Structure and Radical Ontic Structural
Realism'
Radical Ontic Structural Realism
(ROSR) claims that structure exists independently
of objects that may instantiate it. Critics
of ROSR contend that this claim is conceptually
incoherent, insofar as, (i) it entails there can
be relations without relata, and (ii) there is a
conceptual dependence between relations and relata.
In this essay I suggest that (ii) is motivated by
a set-theoretic formulation of structure, and that
adopting a category-theoretic
formulation may provide ROSR with more
support. In particular, I consider how a
category-theoretic formulation of structure can be
developed that denies (ii), and can be made to do
work in the context of formulating theories in
physics.

2013a.

'Effective Field
Theories'
An effective field
theory
(EFT) of a physical system is a theory of the
dynamics of the system at energies small compared
to a given cutoff. For some systems,
low-energy states with respect to this cutoff are
effectively independent of ("decoupled from")
states at high energies. Hence you can study
the low-energy sector of the theory without the
need for a detailed description of the high-energy
sector (this makes calculations easier, plus you
don't have to worry about thorny issues like
renormalizability). Many physicists
currently think that the Standard Model of
particle physics is an example of an EFT of an, as
yet, unknown high-energy theory. This essay
is a general review of EFTs; in particular, it
identifies two conceptually distinct types
("Wilsonian" and "continuum"), and considers how
they might be interpreted, and also what they say
(and do not say) about the notion of emergence.

2011.

'Quantum Field
Theories in Classical Spacetimes and
Particles'
According to a Received View among philosophers,
relativistic quantum field theories (RQFTs) do not
admit particle interpretations. This view
requires that particles be localizable and
countable, and that these characteristics be given
mathematical expression in the forms of local and
unique total number operators. Various
results (the Reeh-Schlieder
theorem, the Unruh Effect,
Haag's Theorem)
then indicate that formulations of RQFTs do not
support such operators. These mathematical
results, however don't hold for non-relativistic
quantum field thelories (NQFTs). I point out
that this is due to the absolute temporal
structure of the classical spacetimes associated
with NQFTs. This seems to suggest that the
choices that the Received View makes in
mathematically representing its intuitions about
the nature of particles are (implicitly) informed
by non-relativistic intuitions.

2010.

'Relativity and
Quantum Field Theories'
Relativistic quantum field theories (RQFTs) are
invariant under the action of the symmetry group
of a Lorentzian
spacetime -- a spacetime that admits a Lorentzian
(i.e.,
"relativistic") metric. Non-relativistic
quantum field theories (NQFTs) are invariant under
the action of the symmetry group of a classical
spacetime -- a spacetime that minimally admits
separate absolute spatial and temporal
metrics. This essay is concerned with
cashing out two implications of this basic
difference. First, it suggests that a
Received View that claims RQFTs cannot support
particle interpretations is perhaps implicitly
biased with non-relativistic intuitions (this is
argued for in more detail in 2011a). Second,
the relations between RQFTs and NQFTs also suggest
that routes to quantum gravity are more varied
than is typically acknowledged. In
particular, they suggest it should be conceptually
possible to construct a quantum theory of gravity
by taking the "thermodynamic limit" of a
relativistic quantum "particle" (i.e., finite
degrees of freedom) theory of gravity (although I
have no idea how this might be made more precise).

2008.

'Condensed
Matter Physics and the Nature of
Spacetime'
Some condensed matter systems exhibit
low-energy behavior that can be described by
effective field theories that are formally
similar to field theories that appear in other
areas of physics. The "acoustic"
spacetime research programme, for instance, is
based on modeling general relativity by the
low-energy behavior of superfluid Helium 4
(and similar systems). Aspects of the Standard
Model of particle physics can be modeled by
the low-energy behavior of superfluid Helium
3-A, and aspects of conformal field theories
(for which twistors
come in handy) can be modeled by the
low-energy behavior of the edge of
4-dimensional quantum Hall liquids. This
paper evaluates such examples and considers
what they have to tell us about the nature of
spacetime; in particular, how they might
impact the debate between substantivalists and
relationalists.

2006.

'Spacetime
Structuralism'
This paper goes hog-wild with a number
of different mathematical formalisms (twistors,
Einstein algebras, geometric algebra)
that can be used to formulate classical field
theories. The point is to indicate that
if you're predisposed to read ontology off of
your formalism, then you'd be advised to dig
deep and go for some notion of structure,
seeing as how alternative formalisms can be
very different beasts, indeed.

2004.

'Theories of
Newtonian Gravity and Empirical
Indistinguishability'
There's not just one, but many
theories of Newtonian gravity. Some are
in flat spacetime, others are in curved
spacetime. Are they really different
theories, or just different ways of
formulating the same basic theory?
Inquiring minds want to know...

2003.

'Einstein Algebras
and the Hole Argument'
Einstein algebras are abstract
algebras that encode the essential structure
associated with general relativity (GR).
They've been suggested, and rejected, as a way
to avoid the Infamous Hole Argument
against one way of interpreting GR. This
paper points out that some physicists are
trying to use them to construct theories of
quantum gravity, and that this gives them a
bit more respectability than they've typically
been afforded.

'Weinberg on
QFT: Demonstrative Induction and
Underdetermination'
This paper reviews an argument by
Steven Weinberg that seeks to establish a
particular formulation of quantum field theory
as the only type of quantum theory in accord
with the relevent evidence and satisfying two
basic physical principles. The paper
reconstructs Weinberg's argument as a
demonstrative induction and indicates it’s
role as a (potential) foil to the
underdetermination arugment in the debate over
scientific realism.

'Motivating
Structural Realist Interpretations of
Spacetime'
Our best theory of spacetime, general relativity
(GR), admits different mathematical formulations
which, if read literally, disagree at the level of
individuals-based ontology. This suggests a
structural realist
interpretation of GR that commits to the structure
that all such alternative formulations have in
common. However, some authors have observed
that different formulations of the same theory not
only underdetermine individuals-based
interpretations, but also the structure these
individuals instantiate; hence appeals to
alternative formalisms cannot motivate structural
realism. This essay offers a response by
distinguishing between the dynamical
structure associated with a theory in physics, and
its kinematical
structure. This enables a distinction to be
made between a structural realist interpretation
of a given theory, and a structural realist
interpretation of spacetime, as described by a
given theory. I claim that structural
realist interpretations of different formulations
of GR do not suffer from underdetermination of
dynamical structure; and while different
formulations of GR admit different structural
realist interpretations of spacetime, the
underdetermination involved is less severe than
that associated with individuals. Whereas
the individuals-based ontologies associated with
alternative formulations of spacetime are
in-principle underdetermined, the structures they
instantiate are open to empirical investigation in
the form of extensions of GR. Finally, I
offer a category-theoretic
formulation of kinematical structure and indicate
how this formulation deflects recent criticism of
the ontic structural realist concept of structure
as "relations without relata".

'Towards Structural
Realism'
A paper that's been stewing in its own
juices for a while. It suggests an
epistemological leg for structural
realism to stand on, based on
formal learning theory.