14,837 research outputs found
Quantum causal models, faithfulness and retrocausality
Wood and Spekkens (2015) argue that any causal model explaining the EPRB
correlations and satisfying no-signalling must also violate the assumption that
the model faithfully reproduces the statistical dependences and
independences---a so-called "fine-tuning" of the causal parameters; this
includes, in particular, retrocausal explanations of the EPRB correlations. I
consider this analysis with a view to enumerating the possible responses an
advocate of retrocausal explanations might propose. I focus on the response of
N\"{a}ger (2015), who argues that the central ideas of causal explanations can
be saved if one accepts the possibility of a stable fine-tuning of the causal
parameters. I argue that, in light of this view, a violation of faithfulness
does not necessarily rule out retrocausal explanations of the EPRB
correlations, although it certainly constrains such explanations. I conclude by
considering some possible consequences of this type of response for retrocausal
explanations
Relativistic Constraints for a Naturalistic Metaphysics of Time
The traditional metaphysical debate between static and dynamic views in the
philosophy of time is examined in light of considerations concerning the nature
of time in physical theory. Adapting the formalism of Rovelli (1995, 2004), I
set out a precise framework in which to characterise the formal structure of
time that we find in physical theory. This framework is used to provide a new
perspective on the relationship between the metaphysics of time and the special
theory of relativity by emphasising the dual representations of time that we
find in special relativity. I extend this analysis to the general theory of
relativity with a view to prescribing the constraints that must be heeded for a
metaphysical theory of time to remain within the bounds of a naturalistic
metaphysics
Retrocausality at no extra cost
One obstacle faced by proposals of retrocausal influences in quantum mechanics is the perceived high conceptual cost of making such a proposal. I assemble here a metaphysical picture consistent with the possibility of retrocausality and not precluded by the known physical structure of our reality. I conclude that given the right mix of some reasonable metaphysical and epistemological ingredients there is no conceptual cost to such a picture
Extending the 'Institutional' Turn: Property, Politics and Development Trajectories
development, institutions, comparative political economy
Unspeakable Suspicions: Challenging the Racist Consensual Encounter
[Excerpt] In recent years, law enforcement officials have honed a new technique for fighting the War on Drugs: the suspicionless police sweep of stations and vehicles involved in interstate mass transportation. Single officers or groups of officers approach unfortunate individuals in busses, trains, stations and airline terminals. A targeted traveller is requested to show identification and tickets, explain the purpose of his or her travels, and finally, at times, to consent to a luggage search. As long as a reasonable person would understand that he or she could refuse to cooperate, the encounter between the law-enforcement official and the traveller is deemed consensual, not subject to the constraints of the Fourth Amendment
Diffusion and Velocity Auto-Correlation in Shearing Granular Media
We perform numerical simulations to examine particle diffusion at steady
shear in a model granular material in two dimensions at the jamming density and
zero temperature. We confirm findings by others that the diffusion constant
depends on shear rate as with , and set out to
determine a relation between and other exponents that characterize the
jamming transition. We then examine the the velocity auto-correlation function,
note that it is governed by two processes with different time scales, and
identify a new fundamental exponent, , that characterizes an algebraic
decay of correlations with time
Asymmetric velocity correlations in shearing media
A model of soft frictionless disks in two dimensions at zero temperature is
simulated with a shearing dynamics to study various kinds of asymmetries in
sheared systems. We examine both single particle properties, the spatial
velocity correlation function, and a correlation function designed to separate
clockwise and counter-clockwise rotational fields from one another. Among the
rich and interesting behaviors we find that the velocity correlation along the
two different diagonals corresponding to compression and dilation,
respectively, are almost identical and, furthermore, that a feature in one of
the correlation functions is directly related to irreversible plastic events
Holographic graphene in a cavity
The effective strength of EM interactions can be controlled by confining the fields to a cavity and these effects might be used to push graphene into a strongly coupled regime. We study the similar D3/probe D5 system on a compact space and discuss the gravity dual for a cavity between two mirrors. We show that the introduction of a conformal symmetry breaking length scale introduces a mass gap on a single D5 sheet. Bilayer configurations display exciton condensation between the sheets. There is a first order phase transition away from the exciton condensate if a strong enough magnetic field is applied. We finally map out the phase structure of these systems in a cavity with the presence of mirror reflections of the probes - a mass gap may form through exciton condensation with the mirror image
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