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Publications
1.
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'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. |
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'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.
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3.
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'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...
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4.
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'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.
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5.
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'What
Should Philosophers of Science Learn
from the History of the Electron?' (with John Norton)
That it's structure that's retained across
theory-change, and that structure is kinda hard to define in a precise
way (although we do make an effort).
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6.
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'Against
Particle/Field Duality: Asymptotic Particle States and
Interpolating
Fields in Interacting QFT (or: Who's Afraid of Haag's Theorem?)'
This paper tries to indicate how the LSZ
formalism that's used by practicing physicists suggests ways of
interpreting fuzzy concepts like "particle" and "localization" in
quantum field theory (as well as dealing with Haag's Theorem).
And that these ways are to be preferred to
the ways suggested by more abstract (and expressively incomplete)
formalisms (like the algebraic formalism).
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7.
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'The
Coordinate-Independent 2-component Spinor Formalism and the
Conventionality
of Simultaneity'
Some philosophers of spacetime have claimed
that the structure associated with half-integer-spin (fermionic) fields
can settle the debate over the conventionality
of simultaneity. This paper disputes this claim, in
particular by calling attention to how fermionic fields can be
represented in a manifestly coordinate-independent way.
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8.
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'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.
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9.
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'Whitehead's
Theory of Gravity'
Everything you ever wanted to know about
Whitehead's theory of gravity...
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Drafts
1.
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'Relativity
and Quantum Field Theories'
Relativistic quantum field theories (RQFTs) are invariant under the
action of the Poincaré group, the symmetry group of Minkowski
spacetime. Non-relativistic quantum field theories (NQFTs) are
invariant under the action of the symmetry group of a classical
spacetime; i.e., a spacetime
that minimally admits absolute spatial and temporal metrics. This
essay is concerned with cashing out two implications of this basic
difference. First, under a Received View, RQFTs do not admit
particle interpretations. I argue that the concept of particle
that informs this view is motivated by non-relativistic intuitions
associated with the structure of classical spacetimes, and hence should
be abandoned. Second, the relations between RQFTs and NQFTs also
suggest that routes to quantum gravity are more varied than is
typically acknowledged. The second half of this essay is
concerned with mapping out some of this conceptual space. |
| 2. |
'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 results, however, do not hold for
non-relativistic quantum field thelories (NQFTs). I argue that
this is due to the absolute structure of the classical spacetimes
associated with such theories. This suggests that the intuitions
that underlie the Received View are non-relativistic. Thus, to
the extent that such intuitions are inappropriate in the relativistic
context, they should be abandoned when it comes to interpreting RQFTs. |
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'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". |
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'Condensed
Matter Physics and the
Nature of Spacetime, Version 1'
The bloated companion to Publication #1 above.
Includes
reviews
of some 2-dim EFTs in condensed matter systems.
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5.
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'Algebraic
Substantivalism and the Hole Argument'
The bloated companion to Publication #4 above.
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6.
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'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.
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Projects
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'Effective Field Theories and
Intertheoretic Relations'
This
essay provides a review of effective field theoretic
techniques and their philosophical import with respect to issues such
as reduction, explanation, and intertheoretic relations. 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 cut-off. For some systems, low-ener'gy
states with respect to this cut-off are effectively independent of
("decoupled from") states at high energies. Hence one may study
the low-energy sector of the theory without the need for a detailed
description of the high-energy sector. Systems that admit EFTs
appear in both relativistic quantum field theory and condensed matter
physics. In the latter case, the "fundamental" theory is
typically known, and the effective theory may be obtained by taking an
appropriate low-energy limit. In the former case, the fundamental
theory may not be known, and the effective theory can only be obtained
by imposing symmetry and "naturalness" constraints on candidate
Langrangians.
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