49,090 research outputs found
Weak Pseudo-Rationalizability
This paper generalizes rationalizability of a choice function by a single acyclic binary relation to
rationalizability by a set of such relations. Rather than selecting those options in a menu that are
maximal with respect to a single binary relation, a weakly pseudo-rationalizable choice function
selects those options that are maximal with respect to at least one binary relation in a given
set. I characterize the class of weakly pseudo-rationalizable choice functions in terms of simple
functional properties. This result also generalizes Aizerman and Malishevski's characterization
of pseudo-rationalizable choice functions, that is, choice functions rationalizable by a set of total
orders
The perils of identity fraud
Among the fastest growing crimes in the country, identity fraud involves the acquisition of credit in someone else's name. What can you do to protect yourself? Julia Stewart of the Federal Reserve Bank of Boston explains.Consumer credit ; False personation ; Identification cards - Forgeries ; Fraud
Obligation, Permission, and Bayesian Orgulity
This essay has two aims. The first is to correct an increasingly popular way of misunderstanding Belot's Orgulity Argument. The Orgulity Argument charges Bayesianism with defect as a normative epistemology. For concreteness, our argument focuses on Cisewski et al.'s recent rejoinder to Belot. The conditions that underwrite their version of the argument are too strong and Belot does not endorse them on our reading. A more compelling version of the Orgulity Argument than Cisewski et al. present is available, however---a point that we make by drawing an analogy with de Finetti's argument against mandating countable additivity. Having presented the best version of the Orgulity Argument, our second aim is to develop a reply to it. We extend Elga's idea of appealing to finitely additive probability to show that the challenge posed by the Orgulity Argument can be met
Another Approach to Consensus and Maximally Informed Opinions with Increasing Evidence
Merging of opinions results underwrite Bayesian rejoinders to complaints about the subjective nature of personal probability. Such results establish that sufficiently similar priors achieve consensus in the long run when fed the same increasing stream of evidence. Initial subjectivity, the line goes, is of mere transient significance, giving way to intersubjective agreement eventually. Here, we establish a merging result for sets of probability measures that are updated by Jeffrey conditioning. This generalizes a number of different merging results in the literature. We also show that such sets converge to a shared, maximally informed opinion. Convergence to a maximally informed opinion is a (weak) Jeffrey conditioning analogue of Bayesian “convergence to the truth” for conditional probabilities. Finally, we demonstrate the philosophical significance of our study by detailing applications to the topics of dynamic coherence, imprecise probabilities, and probabilistic opinion pooling
Persistent Disagreement and Polarization in a Bayesian Setting
For two ideally rational agents, does learning a finite amount of shared evidence necessitate agreement? No. But does it at least guard against belief polarization, the case in which their opinions get further apart? No. OK, but are rational agents guaranteed to avoid polarization if they have access to an infinite, increasing stream of shared evidence? No
The case of muddled units in temporal discounting
While parameters are crucial components of cognitive models, relatively little importance has been given to their units. We show that this has lead to some parameters to be contaminated, introducing an artifactual correlation between them. We also show that this has led to the illegal comparison of parameters with different units of measurement – this may invalidate parameter comparisons across participants, conditions, groups, or studies. We demonstrate that this problem affects two related models: Stevens' power law and Rachlin's delay discounting model. We show that it may even affect models which superficially avoid the incompatible units problem, such as hyperbolic discounting. We present simulation results to demonstrate the extent of the issues caused by the muddled units problem. We offer solutions in order to avoid the problem in the future or to aid in re-interpreting existing datasets
Collisions Between Gravity-Dominated Bodies: 1. Outcome Regimes and Scaling Laws
Collisions are the core agent of planet formation. In this work, we derive an
analytic description of the dynamical outcome for any collision between
gravity-dominated bodies. We conduct high-resolution simulations of collisions
between planetesimals; the results are used to isolate the effects of different
impact parameters on collision outcome. During growth from planetesimals to
planets, collision outcomes span multiple regimes: cratering, merging,
disruption, super-catastrophic disruption, and hit-and-run events. We derive
equations (scaling laws) to demarcate the transition between collision regimes
and to describe the size and velocity distributions of the post-collision
bodies. The scaling laws are used to calculate maps of collision outcomes as a
function of mass ratio, impact angle, and impact velocity, and we discuss the
implications of the probability of each collision regime during planet
formation.
The analytic collision model presented in this work will significantly
improve the physics of collisions in numerical simulations of planet formation
and collisional evolution. (abstract abridged)Comment: Version 3, accepted to ApJ in Nov. 2011 published online Dec. 2011.
Abstract abridge
Shock wave propagation in porous ice
We present data on shock wave propagation in porous ice under conditions applicable to the outer solar system. The equation of state of porous ice under low temperature and low pressure conditions agrees well with measurements under terrestrial conditions implying that data on terrestrial snow may be applicable to the outer solar system. We also observe rarefaction waves from small regions of increased porosity and calculate release wave velocities
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