Analytic DC thermo-electric conductivities in holography with massive gravitons

We provide an analytical derivation of the thermo-electric transport coefficients of the simplest momentum-dissipating model in gauge/gravity where the lack of momentum conservation is realized by means of explicit graviton mass in the bulk. We rely on the procedure recently described by Donos and Gauntlett in the context of Q-lattices and holographic models where momentum dissipation is realized through non-trivial scalars. The analytical approach confirms the results found previously by means of numerical computations.Comment: 9 pages, no figures, minor comments added, version to appear on PR

Electromagnetic response of strongly coupled plasmas

We present a thorough analysis of the electromagnetic response of strongly coupled neutral plasmas described by the gauge/gravity correspondence. The coupling of the external electromagnetic field with the tower of quasi-normal modes of the plasmas supports the presence of various electromagnetic modes with different properties. Among them we underline the existence of negative refraction with low dissipation for a transverse non-hydrodynamical mode. Previous hydrodynamical approaches have shown the ubiquitous character of negative refraction in charged plasmas and the absence thereof in neutral plasmas. Our results here extend the analysis for neutral plasmas beyond the hydrodynamical regime. As an application of these new insights we briefly discuss the case of the quark gluon plasma in the temperature dominated regime.Comment: 29 pages, 15 figure

An Improved Calculation of the Non-Gaussian Halo Mass Function

The abundance of collapsed objects in the universe, or halo mass function, is an important theoretical tool in studying the effects of primordially generated non-Gaussianities on the large scale structure. The non-Gaussian mass function has been calculated by several authors in different ways, typically by exploiting the smallness of certain parameters which naturally appear in the calculation, to set up a perturbative expansion. We improve upon the existing results for the mass function by combining path integral methods and saddle point techniques (which have been separately applied in previous approaches). Additionally, we carefully account for the various scale dependent combinations of small parameters which appear. Some of these combinations in fact become of order unity for large mass scales and at high redshifts, and must therefore be treated non-perturbatively. Our approach allows us to do this, and to also account for multi-scale density correlations which appear in the calculation. We thus derive an accurate expression for the mass function which is based on approximations that are valid over a larger range of mass scales and redshifts than those of other authors. By tracking the terms ignored in the analysis, we estimate theoretical errors for our result and also for the results of others. We also discuss the complications introduced by the choice of smoothing filter function, which we take to be a top-hat in real space, and which leads to the dominant errors in our expression. Finally, we present a detailed comparison between the various expressions for the mass functions, exploring the accuracy and range of validity of each.Comment: 28 pages, 13 figures; v2: text reorganized and some figured modified for clarity, results unchanged, references added. Matches version published in JCA

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Pacific Rim Magazine 2011

The 2011 issue of Pacific Rim Magazine includes the cover stories "Dayton Boots' Canadian Sale," "Angus An Gets Grilled," "Mars to Venus: Thailand's Third Gender," and "David Y. H. Lui.

The International Opening of Small District Firms. Flexibility Vs. Consolidation in Channel Relations

none2The following study is concerned with an Italian industrial district that has been studied for a period of 18 years. This has made possible the construction of a taxonomy based on dynamic profiles of exporting firms, whose characters have been examined in their main changing patterns. The results of the research attest the presence of definite district economies along the distribution channels, that allow the enterprises to increase their competitiveness on a flexibility base, in spite of efficiency. The study tries to understand how much this condition, that prevents a radication in market relations, could remain an internationalization alternative model and a complementary behavior compared with those characterized by aopenC. Pepe ; F. MussoC., Pepe; Musso, Fabi