Qubit authentication

Secure communication requires message authentication. In this paper we address the problem of how to authenticate quantum information sent through a quantum channel between two communicating parties with the minimum amount of resources. Specifically, our objective is to determine whether one elementary quantum message (a qubit) can be authenticated with a key of minimum length. We show that, unlike the case of classical-message quantum authentication, this is not possible.Comment: LaTeX, 8 page

University-industry linkages and the role of the geographical proximity

The main aim of this paper is to exam the local dimension of the university and industry linkages. It is widely recognized in the literature that academic research is an important source of new knowledge to the innovative efforts of the firms. Many authors, such as Audrescht and Feldman (1996), Acs and Varga (2005), Breschi and Lissoni (2009), have shown that academic research is positively correlated with firms’ innovation at the geographical level. There are two reasons that are pointed out for this correlation. First, there are many ways in which knowledge generated by academic research can spill over to the firms, such as research papers, patents and informal contacts. Second, geographical proximity can encourage cooperation between academic researchers and the R&D staff in the firms. In this way, this paper tries to measure empirically the geographical dimension of the university-industry linkages in Brazil, in the same way to the first effort presented in ERSA 2010 (Garcia et al, 2010). To do that, it was used data from the Brazilian Research Council (CNPq), collected at the CNPq Directory of Research Groups of Brazilian universities. The data shows that in 2008 there were 22,797 research groups from 422 institutions. Among these research groups, 2,726 declared that they have interactions with more than 3,800 firms, which means 5,132 interactions between university and industry. Data were organized both in firm-level and in research group-level; allow the identification of the localization of the firm and of the research group. Among the 5,132 interactions between firms and research groups, it was possible to see that 43.6% of interactions occur inside the same city; 51.2% inside the same region; and 75.3% in the same state. These results show the importance of the local dimension of the interactions between academic research of the university and innovative efforts of the firms. In addition, it was done some empirical tests in order to identify the main factors that contribute to foster university-industry linkages.

Spatial Coherence Resonance near Pattern-Forming Instabilities

The analogue of temporal coherence resonance for spatial degrees of freedom is reported. Specifically, we show that spatiotemporal noise is able to optimally extract an intrinsic spatial scale in nonlinear media close to (but before) a pattern-forming instability. This effect is observed in a model of pattern-forming chemical reaction and in the Swift-Hohenberg model of fluid convection. In the latter case, the phenomenon is described analytically via an approximate approach.Comment: 4 pages, 4 figure

Topological vortices in generalized Born-Infeld-Higgs electrodynamics

A consistent BPS formalism to study the existence of topological axially symmetric vortices in generalized versions of the Born-Infeld-Higgs electrodynamics is implemented. Such a generalization modifies the field dynamics via introduction of three non-negative functions depending only in the Higgs field, namely, $G(|\phi|)$, $w(|\phi|)$ and $V(|\phi|)$. A set of first-order differential equations is attained when these functions satisfy a constraint related to the Ampere law. Such a constraint allows to minimize the system energy in such way that it becomes proportional to the magnetic flux. Our results provides an enhancement of topological vortex solutions in Born-Infeld-Higgs electrodynamics. Finally, we analyze a set of models such that a generalized version of Maxwell-Higgs electrodynamics is recovered in a certain limit of the theory.Comment: 8 pages, 8 figures, to appear in EPJ

Desenvolupament d'una aplicació per a l'estudi d'arcs d'obra de fàbrica mitjantçant anàlisi límit

El contingut de la present tesina està estructurat en tres grans blocs. Per una banda hi ha un anàlisi exhaustiu de les tècniques i les teories aparegudes al llarg dels anys per al disseny de construccions amb arcs d’obra de fàbrica. El següent bloc conté l’explicació detallada de l’aplicació creada per analitzar les construccions amb arcs d’obra de fàbrica. Per una banda hi ha una explicació dels mètode utilitzat per a l’elaboració de l’aplicació i els algoritmes, amb les corresponents justificacions per a cada decisió presa, i per l’altra una guia d’ús de l’aplicació que permeti a l’usuari conèixer i entendre totes les eines disponibles. Finalment s’han analitzat dos exemples reals utilitzant l’aplicació elaborada, amb l’objectiu de calibrar-la i validar-ne el seu ús