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Publications (45)
The notions of two-dimensional area, Killing fields and matter flux are introduced in the setting of causal fermion systems. It is shown that for critical points of the causal action, the area change of two-dimensional surfaces under a Killing flow in null directions is proportional to the matter flux through these surfaces. This relation generaliz...
I argue that, contrary to the standard view, one cannot understand the structure and nature of our knowledge in physics without an analysis of the way that observers (and, more generally, measuring instruments and experimental arrangements) are modeled in theory. One upshot is that standard pictures of what a scientific theory can be are grossly in...
quantum-gravity corrections (in the form of a minimal length) to the Feynman propagator for a free scalar particle in R D are shown to be the result of summing over all dimensions D ′ ≥ D of R D ′ , each summand taken in the absence of quantum gravity.
We study black holes produced via collapse of a spherically symmetric charged scalar field in asymptotically flat space. We employ a late time expansion and argue that decaying fluxes of radiation through the event horizon imply that the black hole must contain a null singularity on the Cauchy horizon and a central spacelike singularity.
Quantum-gravity corrections (in the form of a minimal length) to the Feynman propagator for a free scalar particle in $\mathbb{R}^D$ are shown to be the result of summing over all dimensions $D'\geq D$ of $\mathbb{R}^{D'}$, each summand taken in the absence of quantum gravity.
The notions of two-dimensional area, Killing fields and matter flux are introduced in the setting of causal fermion systems. It is shown that for critical points of the causal action, the area change of two-dimensional surfaces under a Killing flow in null directions is proportional to the matter flux through these surfaces. This relation generaliz...
We numerically solve Einstein’s equations coupled to a scalar field in the interior of Kerr black holes. We find shock waves form near the inner horizon. The shocks grow exponentially in amplitude and need not be axisymmetric. Observers who pass through the shocks experience exponentially large tidal forces and are accelerated exponentially close t...
I argue that, contrary to the standard view, one cannot understand the structure and nature of our knowledge in physics without an analysis of the way that observers (and, more generally, measuring instruments and experimental arrangements) are modeled in theory. One upshot is that standard pictures of what a scientific theory can be are grossly in...
I argue that, contrary to the standard view, one cannot understand the structure and nature of our knowledge in physics without an analysis of the way that observers (and, more generally, measuring instruments and experimental arrangements) are modeled in theory. One upshot is that standard pictures of what a scientific theory can be are grossly in...
We study black holes produced by the collapse of a spherically symmetric charged scalar field in asymptotically flat space. We employ a late time expansion and show decaying fluxes of radiation through the event horizon imply the black hole must contain a null singularity on the Cauchy horizon and a central spacelike singularity.
Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevan...
The question of the existence of gravitational stress-energy in general relativity has exercised investigators in the field since the inception of the theory. Folklore has it that no adequate definition of a localized gravitational stress-energetic quantity can be given. Most arguments to that effect invoke one version or another of the Principle o...
We numerically solve Einstein's equations coupled to a scalar field in the interior of Kerr black holes. We find shock waves form near the inner horizon. The shocks grow exponentially in amplitude and need not be axisymmetric. Our numerical results are consistent with the geometry inside the inner horizon exponentially collapsing to zero volume, me...
Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevan...
Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevan...
The analysis of theory-confirmation generally takes the form: show that a theory in conjunction with physical data and auxiliary hypotheses yield a prediction about phenomena; verify the prediction; provide a quantitative measure of the degree of theory-confirmation this yields. The issue of confirmation for an entire framework (e.g., Newtonian mec...
An energy condition, in the context of a wide class of spacetime theories (including general relativity), is, crudely speaking, a relation one demands the stress-energy tensor of matter satisfy in order to try to capture the idea that “energy should be positive”. The remarkable fact I will discuss in this paper is that such simple, general, almost...
I examine the debate between substantivalists and relationalists about the ontological character of spacetime and conclude it is not well posed. I argue that the Hole Argument does not bear on the debate, because it provides no clear criterion to distinguish the positions. I propose two such precise criteria and construct separate arguments based o...
Every physical theory has (at least) two different forms of mathematical equations to represent its target systems: the dynamical (equations of motion) and the kinematical (kinematical constraints). Kinematical constraints are differentiated from equations of motion by the fact that their particular form is fixed once and for all, irrespective of t...
The standard argument for the uniqueness of the Einstein field equation is
based on Lovelock's Theorem, the relevant statement of which is restricted to
four dimensions. I prove a theorem similar to Lovelock's, with a physically
modified assumption: that the geometric object representing curvature in the
Einstein field equation ought to have the ph...
I state and prove, in the context of a space having only the
metrical structure imposed by the geometrized version of Newtonian
gravitational theory, a theorem analagous to that of Weyl's in a
Lorentzian space. The theorem, loosely speaking, says that a
projective structure and a suitably defined compatible conformal
structure on such a space joint...
General relativity poses serious problems for counterfactual propositions
peculiar to it as a physical theory. Because these problems arise solely from
the dynamical nature of spacetime geometry, they are shared by all schools of
thought on how counterfactuals should be interpreted and understood. Given the
role of counterfactuals in the characteri...
I examine the debate between substantivalists and relationalists about the ontological character of spacetime and conclude it is not well posed. I argue that the hole argument does not bear on the debate, because it provides no clear criterion to distinguish the positions. I propose two such precise criteria and construct separate arguments based o...
In the early 1970s it is was realized that there is a striking formal analogy
between the Laws of black-hole mechanics and the Laws of classical
thermodynamics. Before the discovery of Hawking radiation, however, it was
generally thought that the analogy was only formal, and did not reflect a deep
connection between gravitational and thermodynamica...
The question of the existence of gravitational stress-energy in
general relativity has exercised investigators in the field since
the inception of the theory. Folklore has it that no adequate
definition of a localized gravitational stress-energetic quantity
can be given. Most arguments to that effect invoke one version or
another of the Principle o...
An energy condition, in the context of a wide class of spacetime theories
(including general relativity), is, crudely speaking, a relation one demands
the stress-energy tensor of matter satisfy in order to try to capture the idea
that "energy should be positive". The remarkable fact I will discuss in this
paper is that such simple, general, almost...
In the early 1970s it is was realized that there is a striking
formal analogy between the Laws of black-hole mechanics and the Laws
of classical thermodynamics. Before the discovery of Hawking
radiation, however, it was generally thought that the analogy was
only formal, and did not reflect a deep connection between
gravitational and thermodynamica...
General relativity poses serious problems for counterfactual
propositions peculiar to it as a physical theory, problems that have
gone unremarked on in the physics and in the philosophy literature.
Because these problems arise from the dynamical nature of spacetime
geometry, they are shared by all schools of thought on how
counterfactuals should be...
I do not think the notion of rigidity in designation can be correct, at least not in any way that can serve to ground a semantics purports both to be fundamental in a semiotical sense and to the best science of the day. A careful examination of both content and the character of our best scientific knowledge not cannot support anything like what the...
I explain the difficulty of making various concepts of and relating
to probability precise, rigorous and physically significant when
attempting to apply them in reasoning about objects
(e.g., spacetimes) living in infinite-dimensional
spaces, working through many examples from cosmology. I focus on
the relation of topological to measure-theoretic n...
One can (for the most part) formulate a model of a classical system
in either the Lagrangian or the Hamiltonian framework. Though it is
often thought that those two formulations are equivalent in all
important ways, this is not true: the underlying geometrical
structures one uses to formulate each theory are not isomorphic.
This raises the question...
The vague accuracies of events dancing two and two with language which they forever surpass William Carlos Williams Paterson In theory, there's no difference between theory and practice. In practice, there is. Yogi Berra ABSTRACT I argue that an adequate semantics for physical theories must be grounded on an account of the way that a theory provide...
One can (for the most part) formulate a model of a classical system in either the Lagrangian or the Hamiltonian framework. Though it is often thought that those two formulations are equivalent in all important ways, this is not true: the underlying geometrical structures one uses to formulate each theory are not isomorphic. This raises the question...
The question of the existence of gravitational stress-energy in general
relativity has exercised investigators in the field since the inception of the
theory. Folklore has it that no adequate definition of a localized
gravitational stress-energetic quantity can be given. Most arguments to that
effect invoke one version or another of the Principle o...
I argue that, contrary to the recent claims of physicists and philosophers of physics, general relativity requires no interpretation in any substantive sense of the term. I canvass the common reasons given in favor of the alleged need for an interpretation, including the difficulty in coming to grips with the physical significance of diffeomorphism...
The dispute over the viability of various theories of relativistic,
dissipative fluids is analyzed. The focus of the dispute is
identified as the question of determining what it means for a theory
to be applicable to a given type of physical system under given
conditions. The idea of a physical theory's regime of
propriety is introduced, in an atte...
Thesis (Ph. D.)--University of Chicago, Dept. of Philosophy, June 2005. Includes bibliographical references.
Much controversy surrounds the question of the proper definition of %ingularity' in general relativity, and the question of whether the prediction of such entities constitutes a crisis for the theory. I argue that a definition in terms of curve incompleteness is adequate, and that the idea that singularities correspond to missing points' faces insu...
I argue that all current research programs in quantum gravity conform to the 17th century hypothetico-deductive model of scientific inquiry, perhaps of necessity given the current state of technology. In so far as they do not recognize and advertise the shortcomings of the research method they use, they do a disservice to the integrity of science,...
alpha 1-Antitrypsin (alpha 1AT) deficiency is a hereditary disorder associated with reduced serum alpha 1AT levels and the development of pulmonary emphysema. An alpha 1AT gene is defined as "Null" when no alpha 1AT in serum is attributed to that alpha 1AT gene. Although all alpha 1AT Null genes have identical phenotypic consequences (i.e. no detec...
Those who make causality one of the original uralt elements in the universe or one of the fundamental categories of thought,—of whom you will find that I am not one,—have one very awkward fact to explain away. It is that men's conceptions of a Cause are in different stages of scientific culture entirely different and inconsistent. The great princip...