Do the Electrons and Ions in X-ray Clusters Share the Same Temperature?

The virialization shock around an X-ray cluster primarily heats the ions, since they carry most of the kinetic energy of the infalling gas. Subsequently, the ions share their thermal energy with the electrons through Coulomb collisions. We quantify the expected temperature difference between the electrons and ions as a function of radius and time, based on a spherical self-similar model for the accretion of gas by a cluster in an Omega=1, h=0.5 universe. Clusters with X-ray temperatures T=(4-10)*10^7 K, show noticeable differences between their electron and ion temperatures at radii >2 Mpc. High resolution spectroscopy with future X-ray satellites such as Astro E may be able to determine the ion temperature in intracluster gas from the width of its X-ray emission lines, and compare it to the electron temperature as inferred from the free-free emission spectrum. Any difference between these temperatures can be used to date the period of time that has passed since the infalling gas joined the cluster.Comment: 18 pages, 3 figures, submitted to Ap

Prioritized Metric Structures and Embedding

Metric data structures (distance oracles, distance labeling schemes, routing schemes) and low-distortion embeddings provide a powerful algorithmic methodology, which has been successfully applied for approximation algorithms \cite{llr}, online algorithms \cite{BBMN11}, distributed algorithms \cite{KKMPT12} and for computing sparsifiers \cite{ST04}. However, this methodology appears to have a limitation: the worst-case performance inherently depends on the cardinality of the metric, and one could not specify in advance which vertices/points should enjoy a better service (i.e., stretch/distortion, label size/dimension) than that given by the worst-case guarantee. In this paper we alleviate this limitation by devising a suit of {\em prioritized} metric data structures and embeddings. We show that given a priority ranking $(x_1,x_2,\ldots,x_n)$ of the graph vertices (respectively, metric points) one can devise a metric data structure (respectively, embedding) in which the stretch (resp., distortion) incurred by any pair containing a vertex $x_j$ will depend on the rank $j$ of the vertex. We also show that other important parameters, such as the label size and (in some sense) the dimension, may depend only on $j$. In some of our metric data structures (resp., embeddings) we achieve both prioritized stretch (resp., distortion) and label size (resp., dimension) {\em simultaneously}. The worst-case performance of our metric data structures and embeddings is typically asymptotically no worse than of their non-prioritized counterparts.Comment: To appear at STOC 201

Blackbox Quantization of Superconducting Circuits using exact Impedance Synthesis

We propose a new quantization method for superconducting electronic circuits involving a Josephson junction device coupled to a linear microwave environment. The method is based on an exact impedance synthesis of the microwave environment considered as a blackbox with impedance function Z(s). The synthesized circuit captures dissipative dynamics of the system with resistors coupled to the reactive part of the circuit in a non-trivial way. We quantize the circuit and compute relaxation rates following previous formalisms for lumped element circuit quantization. Up to the errors in the fit our method gives an exact description of the system and its losses

First-Degree Discrimination by a Duopoly: Pricing and Quality Choice

The paper examines under what conditions vertically differentiated duopolists engage in first-degree price discrimination. Each firm decides on a pricing regime at a first stage and sets prices at a second stage. The paper shows that when unit cost is an increasing and convex function of quality, the discriminatory regime is the unique subgame-perfect equilibrium of such two-stage game. In contrast to the case of horizontal differentiation, the discriminatory equilibrium is not necessarily Pareto-dominated by a bilateral commitment to uniform pricing. Also, the quality choices of perfectly discriminating duopolists are welfare maximizing. The paper explains why a threat of entry may elicit price discrimination by an incumbent monopolist.competition in pricing regimes, duopoly, quality choice

Competition Policy and Innovation

L'article analyse les complémentarités et les tensions entre la concurrence et l'innovation tant du point de vue des instruments d'analyse que du point de vue des politiques économiques.competition for the market; patent thicket; pools

First degree discrimination in a competitive setting : pricing and quality choice

The paper investigates competition in price schedules among vertically differentiated producers. First order price discrimination leading to personalized prices are the perfect equilibrium of the two-stage game where firms choose at the first stage to commit or not to a uniform price and compete at the second stage. Whether the profits earned by both firms are larger or smaller under discrimination than under uniform pricing depends on the quality gap between firms and on the disparity of consumer preferences. Finally, firms engaged in first degree discrimination choose quality levels that are optimal from a welfare perspective.Price discrimination, price schedules, personalized prices, vertical differentiation.

Immigrant Integration and Social Solidarity in a Time of Crisis: Europe and the United States in a Postwelfare State

A cloud has settled over the immigration regimes of the European welfare states and the United States. Confidence has waned in the viability and value of integrating newcomers into a system of social solidarity. The weakening of civic nationalism and secular constitutional patriotism has unsettled national identities and undermined efforts to facilitate the inclusion of immigrants, especially Muslims. More forceful integration policies might better sustain the welfare state, but individual liberties and group recognition make this more difficult. Ironically, immigrants may now fare better in more unjust neoliberal societies such as the United States than in the advanced welfare states. This article looks at Europe (Germany in particular) and the United States to assess recent developments. Current arrangements are inadequate to resolve the dual crisis of integration and solidarity at the very moment that social equality is increasingly undermined by fiscal crises and aggressive neoliberal social policies

Responses of Phycomyces indicating optical excitation of the lowest triplet state of riboflavin

Phototropic and light growth responses of the sporangiophore of Phycomyces have been elicited using tunable laser stimulation from 575 to 630 nm. The growth response shows additional components of the action spectrum with a sharp peak at 595 nm, a sharp cut-off at 585 nm, and a tail extending beyond 630 nm. The integral over the electronic transition (f-value) is 1.5 x 10^-9 times that at 455 nm. These parameters indicate a direct transition from the ground state to the lowest triplet state of riboflavin

Self-avoiding Tethered Membranes at the Tricritical Point

The scaling properties of self-avoiding tethered membranes at the tricritical point (theta-point) are studied by perturbative renormalization group methods. To treat the 3-body repulsive interaction (known to be relevant for polymers), new analytical and numerical tools are developped and applied to 1-loop calculations. These technics are a prerequisite to higher order calculations for self-avoiding membranes. The cross-over between the 3-body interaction and the modified 2-body interaction, attractive at long range, is studied through a new double epsilon-expansion. It is shown that the latter interaction is relevant for 2-dimensional membranes at the theta-point.Comment: 57 pages, gz-compressed ps-fil