REPRESENTATIVE DEMOCRACY: MAKING IT WORK BETTER

Public Economics,

On Stationary, Self-Similar Distributions of a Collisionless, Self-Gravitating, Gas

We study systematically stationary solutions to the coupled Vlasov and Poisson equations which have `self-similar' or scaling symmetry in phase space. In particular, we find analytically {\it all} spherically symmetric distribution functions where the mass density and gravitational potential are strict power laws in $r$, the distance from the symmetry point. We treat as special cases, systems built from purely radial orbits and systems that are isotropic in velocity space. We then discuss systems with arbitrary velocity space anisotropy finding a new and very general class of distribution functions. These distributions may prove useful in modelling galaxies. Distribution functions in cylindrical and planar geometries are also discussed. Finally, we study spatially spheroidal systems that again exhibit strict power-law behaviour for the density and potential and find results in agreement with results published recently.Comment: 23 pages, regular Tex, figures in separate .uu file to follo

Relaxing and Virializing a Dark Matter Halo

Navarro, Frenk, and White have suggested that the density profiles of simulated dark matter halos have a ``universal'' shape so that a given halo can be characterized by a single free parameter which fixes its mass. In this paper, we revisit the spherical infall model in the hope of recognizing in detail the existence and origin of any such universality. A system of particles is followed from linear perturbation, through first shell crossing, then through an accretion or infall phase, and finally to virialization. During the accretion phase, the system relaxes through a combination of phase mixing, phase space instability, and moderate violent relation. It is driven quickly, by the flow of mass through its surface, toward self-similar evolution. The self-similar solution plays its usual role of intermediate attractor and can be recognized from a virial-type theorem in scaled variables and from our numerical simulations. The transition to final equilibrium state once infall has ceased is relatively gentle, an observation which leads to an approximate form for the distribution function of the final system. The infall phase fixes the density profile in intermediate regions of the halo to be close to r^{-2}. We make contact with the standard hierarchical clustering scenario and explain how modifications of the self-similar infall model might lead to density profiles in agreement with those found in numerical simulations.Comment: 26 pages, Latex, plus 11 figure

Debates in allergy medicine: Specific immunotherapy in children with atopic dermatitis, the "con" view.

Atopic dermatitis (AD) is a common chronic skin condition in children that has a proven association with other atopic conditions and allergies. These associations, like the general pathophysiology of AD, are complex and not fully understood. While there is evidence for the efficacy of specific immunotherapy (SIT) in pediatric asthma and allergic rhinitis (AR), there is a lack of strong data to support its use in AD. IgE has been shown to be elevated in many patients with AD, but it is an unreliable biomarker due to variability and great fluctuation over time, poor positive predictive value for clinically relevant allergy, and poor correlation with disease state. In spite of this, almost all studies of SIT use either positive skin prick testing (SPT) or serum specific IgE levels to guide therapy. Allergen avoidance, with some exceptions, is generally not effective at controlling AD in children. The few studies that have investigated the efficacy of SIT in children with AD have produced conflicting results, and a lack of reproducibility with a standard treatment protocol. Limited studies have shown clinical improvement in mild to moderate AD cases, but no effect on more severe patients. Uncontrolled studies are difficult to interpret, due to the natural history of remission or "outgrowing" of AD over time in many patients without specific interventions. Drawbacks to SIT include the length of treatment, poor compliance, cost, and potential side effect profile. The potential for misdirection of time and energy away from skin directed therapy could negatively impact on AD outcomes

An Elliptical Galaxy Luminosity Function and Velocity Dispersion Sample of Relevance for Gravitational Lensing Statistics

We have selected 42 elliptical galaxies from the literature and estimated their velocity dispersions at the effective radius (\sigma_{\re}) and at 0.54 effective radii (\vff). We find by a dynamical analysis that the normalized velocity dispersion of the dark halo of an elliptical galaxy \vdm is roughly \sigma_{\re} multiplied by a constant, which is almost independent of the core radius or the anisotropy parameter of each galaxy. Our sample analysis suggests that \vdm^{*} lies in the range 178-198 km s$^{-1}$. The power law relation we find between the luminosity and the dark matter velocity dispersion measured in this way is (L/L^{*}) = (\vdm/\vdm^{*})^\gamma, where $\gamma$ is between 2-3. These results are of interest for strong gravitational lensing statistics studies. In order to determine the value of \vdm^{*}, we calculate \mstar in the same \bt band in which \vdm^{*} has been estimated. We select 131 elliptical galaxies as a complete sample set with apparent magnitudes \bt between 9.26 and 12.19. We find that the luminosity function is well fitted to the Schechter form, with parameters \mstar = -19.66 + 5$\cdot\log_{10}h \pm 0.30$, $\alpha = 0.15 \pm 0.55$, and the normalization constant $\phi^{*} = (1.34 \pm 0.30) \times 10^{-3} h^{3}$ Mpc$^{-3}$, with the Hubble constant \hnot = 100 $h$ km s$^{-1}$ Mpc$^{-1}$. This normalization implies that morphology type E galaxies make up (10.8 $\pm$ 1.2) per cent of all galaxies.Comment: 18 pages latex, with ps figs included. accepted by New Astronomy (revised to incorporate referees comments

Comment: Monitoring Networked Applications With Incremental Quantile Estimation

Our comments are in two parts. First, we make some observations regarding the methodology in Chambers et al. [arXiv:0708.0302]. Second, we briefly describe another interesting network monitoring problem that arises in the context of assessing quality of service, such as loss rates and delay distributions, in packet-switched networks.Comment: Published at http://dx.doi.org/10.1214/088342306000000600 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

When does a major outbreak become a Public Health Emergency of International Concern?

The process of determining whether a Public Health Emergencies of International Concern (PHEIC) exists and should be declared has drawn increasing criticism over the past few years with allegations that it is more political than technical. Delaying declaration, where appropriate, means that the opportunity of garnering international solidarity and necessary resources in the early phases of epidemics, when public health measures may be more effective, is lost. A reform agenda aimed at enhancing WHO/Emergency Committee transparency and objectivity for the PHEIC declaration process is required

Trust in scientists on climate change and vaccines

On climate change and other topics, conservatives have taken positions at odds with a strong scientific consensus. Claims that this indicates a broad conservative distrust of science have been countered by assertions that while conservatives might oppose the scientific consensus on climate change or evolution, liberals oppose scientists on some other domains such as vaccines. Evidence for disproportionately liberal bias against science on vaccines has been largely anecdotal, however. Here, we test this proposition of opposite biases using 2014 survey data from Oregon and New Hampshire. Across vaccine as well as climate change questions on each of these two surveys, we find that Democrats are most likely to say they trust scientists for information, and Tea Party supporters are least likely, contradicting the proposition of opposite bias. Moreover, partisan divisions tend to widen with education. Theoretical explanations that have been offered for liberal trust or conservative distrust of science in other specific domains such as climate change or environmental protection fit less well with these results on vaccines. Given the much different content of climate change and vaccine issues, the common political pattern appears more consistent with hypotheses of broader ideological divisions on acceptance of science

Structure and Properties of Hughston's Stochastic Extension of the Schr\"odinger Equation

Hughston has recently proposed a stochastic extension of the Schr\"odinger equation, expressed as a stochastic differential equation on projective Hilbert space. We derive new projective Hilbert space identities, which we use to give a general proof that Hughston's equation leads to state vector collapse to energy eigenstates, with collapse probabilities given by the quantum mechanical probabilities computed from the initial state. We discuss the relation of Hughston's equation to earlier work on norm-preserving stochastic equations, and show that Hughston's equation can be written as a manifestly unitary stochastic evolution equation for the pure state density matrix. We discuss the behavior of systems constructed as direct products of independent subsystems, and briefly address the question of whether an energy-based approach, such as Hughston's, suffices to give an objective interpretation of the measurement process in quantum mechanics.Comment: Plain Tex, no figure