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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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'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
Current/Ongoing Projects
1.
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'Intertheoretic Implications of
Non-Relativistic Quantum Field Theories'
This essay considers what non-relativistic quantum field theories
(NQFTs) suggest
about the intertheoretic relations between classical and quantum
theories of particles and fields, both in the presence and in the
absence of gravitational effects. In the absence of gravity,
interacting NQFTs exist for which Haag's theorem, the CPT theorem, and the Spin-Statistics theorem all do
not apply; and
while the Reeh-Schlieder theorem is valid,
it does not have the same
implications as it does in the relativistic context. Moreover, a
consistent NQFT exists that includes gravitational
effects. This "Newtonian" quantum theory of gravity is an example
of an NQFT in a classical curved spacetime, and is not afflicted by the
conceptual problems surrounding relativistic QFTs in curved
spacetimes. These examples provide clues to how the fundamental
theories in physics relate to each other and to the quest of
formulating a fully relativistic quantum theory of gravity.
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2.
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'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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3.
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'Motivating Structural Realist
Interpretations of Spacetime'.
Our best theory of spacetime, general relativity (GR), admits
alternative 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 philosophers (e.g.,
Pooley 2006) have observed that, in general, different formulations of
the same theory not only underdetermine individuals-based
interpretations of the theory, but also the structure these individuals
instantiate. In response, I first distinguish between a
structural realist interpretation of a given theory, versus a
structural realist interpretation of spacetime, as described by a given
theory. I claim that structural realist interpretations of
different formulations of a single theory do not suffer from
underdetermination of structure, appropriately construed. Second,
while different formulations of GR (for instance) 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. For instance, different approaches to
quantum gravity suggest different formulations of GR, which
subsequently suggest different types of spacetime structure. Thus
a semantic realist, who desires to read our best theories literally,
should commit to no more than a structural realist interpretation of
spacetime, allowing that just what this structure is may be empirically
determined by future theories.
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