Quantum wideband traveling-wave analysis of a degenerate parametric amplifier

We develop a wideband traveling-wave formalism for analyzing quantum mechanically a degenerate parametric amplifier. The formalism is based on spatial differential equations-spatial Langevin equations-that propagate temporal Fourier components of the field operators through the nonlinear medium. In addition to the parametric nonlinearity, the Langevin equations include absorption and associated fluctuations, dispersion (phase mismatching), and pump quantum fluctuations. We analyze the dominant effects of phase mismatching and pump quantum fluctuations on the squeezing produced by a degenerate parametric amplifier

Product Variety and Demand Uncertainty

We show that demand uncertainty leads to vertical product differentiation even when consumers are homogeneous. When a firm anticipates that its inventory or capacity may not be fully utilized, product variety can reduce its expected costs of excess capacity. When the firm offers a continuum of product varieties, the highest quality product has the highest profit margins but the lowest percentage margin, while the lowest quality product has the highest percentage margin but the lowest absolute margin. We derive these results in both a monopoly model and a variety of different competitive models. We conclude with a discussion of empirical predictions together with a brief discussion of supporting evidence available from marketing studies.

Graphical description of the action of Clifford operators on stabilizer states

We introduce a graphical representation of stabilizer states and translate the action of Clifford operators on stabilizer states into graph operations on the corresponding stabilizer-state graphs. Our stabilizer graphs are constructed of solid and hollow nodes, with (undirected) edges between nodes and with loops and signs attached to individual nodes. We find that local Clifford transformations are completely described in terms of local complementation on nodes and along edges, loop complementation, and change of node type or sign. Additionally, we show that a small set of equivalence rules generates all graphs corresponding to a given stabilizer state; we do this by constructing an efficient procedure for testing the equality of any two stabilizer graphs.Comment: 14 pages, 8 figures. Version 2 contains significant changes. Submitted to PR

Rudder-Propeller-Hull Interaction: The Results of Some Recent Research, In-Service Problems and their Solutions

The paper describes some recent rudder research that has been carried out by Lloyd’s Register that underlines the importance of rudder-propeller-hull interaction in design, both in terms of the flow field properties around the rudder and also the implications for the rudder’s contribution to the overall propulsion efficiency. Within this consideration both conventional and variable geometry rudder forms are discussed. Additionally, some recent rudder based problems for a variety of ship types are discussed within the paper together with the lessons learnt. The paper is based on the results of sea trials, computational fluid dynamics studies and model tests and gives recommendations for the alleviation of such problems in the future

The evolution of the star forming sequence in hierarchical galaxy formation models

It has been argued that the specific star formation rates of star forming galaxies inferred from observational data decline more rapidly below z = 2 than is predicted by hierarchical galaxy formation models. We present a detailed analysis of this problem by comparing predictions from the GALFORM semi-analytic model with an extensive compilation of data on the average star formation rates of star-forming galaxies. We also use this data to infer the form of the stellar mass assembly histories of star forming galaxies. Our analysis reveals that the currently available data favour a scenario where the stellar mass assembly histories of star forming galaxies rise at early times and then fall towards the present day. In contrast, our model predicts stellar mass assembly histories that are almost flat below z = 2 for star forming galaxies, such that the predicted star formation rates can be offset with respect to the observational data by factors of up to 2-3. This disagreement can be explained by the level of coevolution between stellar and halo mass assembly that exists in contemporary galaxy formation models. In turn, this arises because the standard implementations of star formation and supernova feedback used in the models result in the efficiencies of these process remaining approximately constant over the lifetime of a given star forming galaxy. We demonstrate how a modification to the timescale for gas ejected by feedback to be reincorporated into galaxy haloes can help to reconcile the model predictions with the data.Comment: 30 Pages, 16 Figures, MNRAS accepte

International terrorism and the american dream: A dialectical fairytale

La construcción que hoy día se hace del terrorismo en el sistema internacional es parte de nuestros mundos de ensueño de consumo masivo confrontado con las imágenes del sueño americano. Estos mundos ideales proporcionan los discursos hegemónicos de una política paneuropea y universalista que asesina a un gran número de civiles inocentes con fines políticos, actos de terrorismo, al mismo tiempo que niega que tales actos constituyan terrorismo. La violencia utilizada se representa como un sacrificio compartido y necesario para el sueño americano, sugiriendo una unidad, de otra manera inexistente, supuestamente en “defensa propia” frente al terrorismo. En realidad, lo que se está consumando no son acciones contra el terrorismo y la guerra de agresión, sino guerra de agresión y terrorismo en sí mismos haciéndose pasar por la defensa de las comunidades imaginadas de la nación y “Occidente”. El artículo hace hincapié especialmente en los medios de comunicación y en las películas de Hollywood, incluyendo las redes sociales. El trabajo se basa en el análisis del sistema-mundo, académicos de Relaciones Internacionales y teóricos de la cultura, los medios y la comunicación para analizar los usos del terrorismo hoy en día. Al mismo tiempo, el artículo se basa en teóricos críticos y en intelectuales públicos, desde Edward Said a Judith Butler o el Papa Francisco, para criticar las oposiciones binarias y orientalistas de los discursos paneuropeos actuales sobre terrorismo internacional, de manera que queden expuestas sus complejidades y realidades, históricamente y en la actualidadToday’s framing of terrorism in the international system is part of our contemporary dreamworlds of mass consumption set against images of the American Dream. These dreamworlds provide the hegemonic discourses of a European universalist foreign policy that kills huge numbers of innocent non-combatants for political purposes, acts of terrorism, while denying that such acts constitute terrorism. The violence used is represented as a necessary and shared sacrifice for the American Dream, suggesting a unity, otherwise lacking, supposedly in “self-defense” against terrorism. In reality, what is being consumed are not actions against terrorism and aggressive war, but aggressive war and terrorism themselves masquerading as a defense of the imagined communities of the nation and “the West”. The focus of this article is especially on media and Hollywood films, including social media. The work draws on both world-systems analysis, international relations scholars, and theorists of culture, media and communication to analyze the uses of terrorism today. Simultaneously the article draws on critical theorists and public intellectuals, from Edward Said to Judith Butler to Pope Francis, to critique the binary Orientalist oppositions of today’s pan-European discourses on international terrorism, in ways that expose their complexities and realities, historically and currentl