On the reflection and transmission of circumferential waves through nozzles

This paper presents a mathematical model for predicting the propagation of circumferential waves (acoustic, entropy and vorticity waves) through an annular nozzle. Combustion chambers in modern aero-engines are typically annular, and so a model for circumferential waves is essential for understanding and predicting both combustion noise and thermoacoustic instabilities for such geometries. The linearised Euler equations are solved using the Magnus expansion to obtain the reflection and transmission coefficients of the annular nozzle for acoustic, entropy and vorticity perturbations. Predictions which account for flow physics, such as a non-zero mean flow angle and the generation of vorticity noise, are obtained for the first time. Results are compared with two numerical methods, showing that the mathematical model is able to predict the transmission and reflection of waves for both compact and non-compact frequencies. The model is used to prove one particularly interesting and relevant feature of annular geometries: the generation of a vorticity wave by the acceleration of a circumferential entropy wave. It is shown that this phenomenon originates from the baroclinic torque in the vorticity equation.</jats:p

Properties of holographic dark energy at the Hubble length

We consider holographic cosmological models of dark energy in which the infrared cutoff is set by the Hubble's radius. We show that any interacting dark energy model, regardless of its detailed form, can be recast as a non interacting model in which the holographic parameter $c^{2}$ evolves slowly with time. Two specific cases are analyzed. We constrain the parameters of both models with observational data, and show that they can be told apart at the perturbative level.Comment: 4 pages, 6 figures. Contribution to the Proceedings ERE201

Crítica a la distinció cultural

This article is a critical reading of the work of Pierre Bourdieu on cultural distinction (La Distinction, 1979). It starts from the premise that the forms of distinctions in each country and in each period of history are extremely different and extraordinarily rich and varied. It must be noted, though, that it is extremely difficult to speak of the phenomenon of distinction in general terms —as Bourdieu does—. The complexity of the phenomenon does not mean, however, that it is impossible to formulate a general theory about the phenomenon of distinction. The criticism of Bourdieu’s work permits us to go a bit further and to propose, modestly, an alternative theory on cultural distinction.En este artículo se realiza una lectura crítica de la obra de Pierre Bourdieu sobre la distinción cultural (La distinción, 1979). Se parte del supuesto que las formas de distinción, en cada país y en cada etapa histórica, adoptan formas particulares extraordinariamente ricas y variadas. Es preciso destacar la dificultad de tratar el tema de la distinción en términos generales —como lo hace Bourdieu—. La complejidad del fenómeno no significa que no se pueda intentar formular una teoría general sobre la distinción. La crítica a la obra de Bourdieu nos permite esbozar, modestamente, una teoría alternativa sobre la distinción cultural

Del sentit de l'honor al sentit de la distinció. Sobre el caràcter fràgil i subtil de la distinció postmoderna

El professor Busquet analitza al llarg d'aquest article la diferència semàntica entre el concepte d'honor i el concepte de distinció en el marc de la societat postmoderna. A partir de diferents reflexions sociològiques contemporànies, Jordi Busquet aporta elements i criteris rigorosos per aclarir ambdós conceptes en un context cultural caracteritzat per l'ambivalència i la pèrdua de cànons