To be or not to be, the importance of Digital Identity in the networked society

The emergence of the web has had a deep impact at different levels of our society, changing the way people connect, interact, share information, learn and work. In the current knowledge economy, participatory media seems to play an important part in everyday interactions. The term “digital identity” is becoming part of both our lexicon and our lives. This paper explores some of the aspect s regarding approaches and practices of educators, using web technologies to foster their digital identity within their networks and, at the same time, developing a social presence to complement their professional and academic profiles. In fact, we think it is imperative to discuss the relationship between our social presence and our professional life, as online the two are often intertwined. We present the issues the web poses through dichotomies: open or closed, genuine or fake, single or multiple. We also comment on different approaches to these dichotomies through examples extracted from recent projects, drawing from user’s experiences in building their digital identities. This paper looks at the importance of digital identity in the current networked society, by reviewing the contemporaneous scenario of the participatory web, raising a set of questions about the advantages and implication of consciously developing one’s digital identity, thus opening the discussion regarding openness, uniqueness and integrity in connection with one’s digital identity. This paper is also a reflection of thinking and practice in progress, drawing from examples and real-life situations observed in a diversity of projects. The issue could be reduced, perhaps, to whether one consciously becomes a part of the digital world or not, and how that participation is managed. It is up to us to manage it wisely, and guide knowledge workers in their journey to create theirs

Chiral transport equation from the quantum Dirac Hamiltonian and the on-shell effective field theory

We derive the relativistic chiral transport equation for massless fermions and antifermions by performing a semiclassical Foldy-Wouthuysen diagonalization of the quantum Dirac Hamiltonian. The Berry connection naturally emerges in the diagonalization process to modify the classical equations of motion of a fermion in an electromagnetic field. We also see that the fermion and antifermion dispersion relations are corrected at first order in the Planck constant by the Berry curvature, as previously derived by Son and Yamamoto for the particular case of vanishing temperature. Our approach does not require knowledge of the state of the system, and thus it can also be applied at high temperature. We provide support for our result by an alternative computation using an effective field theory for fermions and antifermions: the on-shell effective field theory. In this formalism, the off-shell fermionic modes are integrated out to generate an effective Lagrangian for the quasi-on-shell fermions/antifermions. The dispersion relation at leading order exactly matches the result from the semiclassical diagonalization. From the transport equation, we explicitly show how the axial and gauge anomalies are not modified at finite temperature and density despite the incorporation of the new dispersion relation into the distribution function.Comment: 9 pages, no figures. v2: Some comments and more details added, typos fixed and reference list updated. Final version matching the published articl

Dynamical evolution of the chiral magnetic effect: Applications to the quark-gluon plasma

We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon plasma phase, and analyze the dynamical evolution of the chiral magnetic effect in a very simple toy model. We conclude that an existing chiral fermion imbalance in peripheral heavy ion collisions would affect the magnetic field dynamics, and consequently, the charge dependent correlations measured in these experiments.Comment: 41 pages, 14 figures, 3 appendices. Version 2: new global structure (appendix added), more explanations and additional references. Version accepted for publication in Physical Review D journa

Technological Convergence: a Strategic Perspective

The information and communication technologies (ICT) sectors are in a process of technological convergence. Determinant factors in this process are the liberalisation of the telecommunications markets and technological change. Many firms are engaged in a process of mergers and alliances to position themselves in this new framework. Technological and demand uncertainties are very important. Our objective in this paper is to study the economic determinants of the strategies of the firms. With this aim, we review some key technological and demand aspects. We shed some light on the strategic motivations of the firms by establishing a parallel with the evolution of the retailing sector.Technological Convergence; Demand Uncertainty; technological Uncertainty; Technology Life Cycle; Internet; Multimedia; Strategy

Concepciones de algunos profesores de matemáticas de básica secundaria sobre los decimales y su relación, como representación, con los números racionales

Esta investigación enmarcada en el paradigma interpretativo y con una metodología interpretativa, tiene como propósito identificar y caracterizar las concepciones de algunos profesores de matemáticas de básica secundaria, sobre los decimales como representación de los números racionales