First-principles study of lithium-doped carbon clathrates under pressure

We present a theoretical study on the behavior under pressure of the two hypothetical C$_{46}$ and Li$_8$C$_{46}$ type-I carbon clathrates in order to bring new informations concerning their synthesis. Using \textit{ab initio} calculations, we have explored the energetic and structural properties under pressure of these two carbon based cage-like materials. These low-density meta-stable phases show large negative pressure transitions compared to diamond which represent a serious obstacle for their synthesis. However, we evidence that a minimum energy barrier can be reached close to 40 GPa, suggesting that the synthesis of the Li-clathrate under extreme conditions of pressure and temperature may be possible. Electronic band structure with related density of states behavior under pressure as well as the dependence of the active Raman modes with pressure are also examined

Unity of pomerons from gauge/string duality

We develop a formalism where the hard and soft pomeron contributions to high energy scattering arise as leading Regge poles of a single kernel in holographic QCD. The kernel is obtained using effective field theory inspired by Regge theory of a 5-d string theory. It describes the exchange of higher spin fields in the graviton Regge trajectory that are dual to glueball states of twist two. For a specific holographic QCD model we describe Deep Inelastic Scattering in the Regge limit of low Bjorken x, finding good agreement with experimental data from HERA. The observed rise of the effective pomeron intercept, as the size of the probe decreases, is reproduced by considering the first four pomeron trajectories. In the case of soft probes, relevant to total cross sections, the leading hard pomeron trajectory is suppressed, such that in this kinematical region we reproduce an intercept of 1.09 compatible with the QCD soft pomeron data. In the spectral region of positive Maldelstam variable t the first two pomeron trajectories are consistent with current expectations for the glueball spectrum from lattice simulations

Confianza en noticias y fragmentación de mercado: el caso español

The Internet has led to the emergence of new channels of information forming alternatives to traditional media brands, which have changed consumer habits and generated an unprecedented information supply. In this new scenario, some questions have arisen about the relationship between trust and the media. Based on focus groups and a survey of 2,104 people at Spain, this research shows there is a relationship between the degree of perceived trust and the preferences of information consumption. In particular, those who get information from traditional channels show greater trust than those who do through alternative channels such as social media or digital-native media (especially young people). This paper also concludes that the perceived value of traditional journalistic brands with respect to digital-native media is modest in terms of trust, although people still prefer the legacy media when informing themselves about complex and important issues.Internet ha propiciado el nacimiento de nuevos canales de información alternativos a los tradicionales soportes, que han alterado los hábitos de consumo y han generado una oferta informativa sin precedentes. En este nuevo escenario, cabe preguntarse si la opinión pública ha cambiado la relación entre confianza y medios de comunicación. Basada en grupos de discusión y una encuesta a 2.104 españoles, esta investigación demuestra que existe una relación entre el grado de confianza percibido y las preferencias de consumo informativo. En concreto, aquellos que se informan por canales tradicionales muestran mayor confianza que los que lo hacen (sobre todo jóvenes) a través de canales alternativos como los medios sociales o los medios nativos digitales. Asimismo, este artículo expone que el valor percibido de las marcas periodísticas tradicionales respecto a los medios nativos digitales es modesto en términos de confianza, si bien se siguen prefiriendo para estar informados de asuntos complejos e importantes.Internet ha propiciat el naixement de nous canals d'informació alternatius als suports tradicionals, que han alterat els hàbits de consum i han generat una oferta informativa sense precedents. En aquest nou escenari, cal preguntar-se si l'opinió pública ha canviat la relació entre confiança i mitjans de comunicació. Basada en grups de discussió i una enquesta a 2.104 espanyols, aquesta investigació demostra que hi ha una relació entre el grau de confiança percebut i les preferències de consum informatiu. En concret, aquells que s'informen per canals tradicionals mostren més confiança que els que ho fan (sobretot joves) a través de canals alternatius com els mitjans socials o els mitjans nadius digitals. D'altra banda, aquest article exposa que el valor percebut de les marques periodístiques tradicionals pel que fa als mitjans nadius digitals és modest en termes de confiança, tot i que se segueixen preferint per estar informats d'assumptes complexos i importants