Quantum Corrections to the Energy Density of a Homogeneous Bose Gas

Quantum corrections to the properties of a homogeneous interacting Bose gas at zero temperature can be calculated as a low-density expansion in powers of $\sqrt{\rho a^3}$, where $\rho$ is the number density and $a$ is the S-wave scattering length. We calculate the ground state energy density to second order in $\sqrt{\rho a^3}$. The coefficient of the $\rho a^3$ correction has a logarithmic term that was calculated in 1959. We present the first calculation of the constant under the logarithm. The constant depends not only on $a$, but also on an extra parameter that describes the low energy $3\to 3$ scattering of the bosons. In the case of alkali atoms, we argue that the second order quantum correction is dominated by the logarithmic term, where the argument of the logarithm is $\rho a \ell_V^2$, and $\ell_V$ is the length scale set by the van der Waals potential.Comment: 29 pages + 6 figures; section 5.3 rewritte

Effective field theory approach to N=4 supersymmetric Yang-Mills at finite temperature

We study the perturbation expansion of the free energy of N=4 supersymmetric SU(N) Yang-Mills at finite temperature in powers of 't Hooft's coupling g^2 N in the large N limit. Infrared divergences are controlled by constructing a hierarchy of two 3 dimensional effective field theories. This procedure is applied to the calculation of the free energy to order (g^2 N)^(3/2), but it can be extended to higher order corrections.Comment: LaTeX, 10 pages, 1 figure, uses eps

Managing 2.0 newsrooms: insight stories of spontaneous innovation and improvisation

Nowadays audiences love live communication (Deuze, 2011), the possibility of reaching news in real time, receiving contents without the effort of having to search for them. The concept “news now” (Sheller, 2014) is an audience imperative. Previous research show that media have developed in the last decade a great dependence on social networks (Singer et alt, 2011). Source of new audiences, social media are also a space for the verification and localization of new contents. Sometimes these functions has forced to alter editorial models to host viral topics, necessary to try to overcome the crisis of attention particularly concerning in the context of the young people (Boczkowski and Mitchelstein, 2016). Digital media estimate that one third of their visits come from Facebook (Somaya, 2014), a figure that forces them to create specific strategies that ensure the reputation and growth of the company in the 2.0 sphere because the atomization of content causes fragmented and decontextualized audiences to consume individual news. Recently, Emily Bell (2018) confirmed also that Facebook is reshaping newsrooms. From the point of view of the audience, the number of users of Facebook or Twitter in Spain is not reached by any mass media. This context generates a strange symbiosis, which combines the need and the competition that we consider relevant to analyze. One of the routines which come from this relationship has been the integration of soft news on the front page of online media. This practice has also affected media credibility.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Renormalization Effects in a Dilute Bose Gas

The low-density expansion for a homogeneous interacting Bose gas at zero temperature can be formulated as an expansion in powers of $\sqrt{\rho a^3}$, where $\rho$ is the number density and $a$ is the S-wave scattering length. Logarithms of $\rho a^3$ appear in the coefficients of the expansion. We show that these logarithms are determined by the renormalization properties of the effective field theory that describes the scattering of atoms at zero density. The leading logarithm is determined by the renormalization of the pointlike $3 \to 3$ scattering amplitude.Comment: 10 pages, 1 postscript figure, LaTe

A Hybrid Parameterization Technique for Speaker Identification

Classical parameterization techniques for Speaker Identification use the codification of the power spectral density of raw speech, not discriminating between articulatory features produced by vocal tract dynamics (acoustic-phonetics) from glottal source biometry. Through the present paper a study is conducted to separate voicing fragments of speech into vocal and glottal components, dominated respectively by the vocal tract transfer function estimated adaptively to track the acoustic-phonetic sequence of the message, and by the glottal characteristics of the speaker and the phonation gesture. The separation methodology is based in Joint Process Estimation under the un-correlation hypothesis between vocal and glottal spectral distributions. Its application on voiced speech is presented in the time and frequency domains. The parameterization methodology is also described. Speaker Identification experiments conducted on 245 speakers are shown comparing different parameterization strategies. The results confirm the better performance of decoupled parameterization compared against approaches based on plain speech parameterization