arXiv subjects
Publications and source records attributed to Alejandro Rivero.
We report a mass rule of Koide type with inverse shape, \[m_i=M^{(d)} (w_0+w_i)^{-2}.\] It applies to the down-quark sector with numerical precision comparable to that of the direct charged-lepton sum rule $m_i=M^{(l)} (z_0+z_i)^{2}$. For central mass values, Koide ratio reaches exactly $2/3$ near 280 TeV under Standard Model renormalisation-group running. We also review other rules of the direct kind involving quarks.
We propose an interpretation for the adjoint representation of the $SO(32)$ group to classify the scalars of a generic Supersymmetric Standard Model having just three generations of particles, via a flavour group $SU(5)$. We show that this same interpretation arises from a simple postulate of self-consistence of composites for these scalars. The model looks only for colour and electric charge, and it pays the cost of an additional chiral $+4/3$ quark per generation.
We collect and analyse messages exchanged in Twitter using two of the platform's publicly available APIs (the search and stream specifications). We assess the differences between the two samples, and compare the networks of communication reconstructed from them. The empirical context is given by political protests taking place in May 2012: we track online communication around these protests for the period of one month, and reconstruct the network of mentions and re-tweets according to the two samples. We find that the search API over-represents the more central users and does not offer an accurate picture of peripheral activity; we also find that the bias is greater for the network of mentions. We discuss the implications of this bias for the study of diffusion dynamics and collective action in the digital era, and advocate the need for more uniform sampling procedures in the study of online communication.
Between the new physics candidates proposed to explain the $t \bar t$ asymmetry measured in the Tevatron, there are some scalar diquarks with electric charge +4/3. This kind of diquark is also needed to classify all the scalars of the supersymmetric standard model, with three generations, under a global flavour symmetry.
The recent wave of mobilizations in the Arab world and across Western countries has generated much discussion on how digital media is connected to the diffusion of protests. We examine that connection using data from the surge of mobilizations that took place in Spain in May 2011. We study recruitment patterns in the Twitter network and find evidence of social influence and complex contagion. We identify the network position of early participants (i.e. the leaders of the recruitment process) and of the users who acted as seeds of message cascades (i.e. the spreaders of information). We find that early participants cannot be characterized by a typical topological position but spreaders tend to me more central to the network. These findings shed light on the connection between online networks, social contagion, and collective dynamics, and offer an empirical test to the recruitment mechanisms theorized in formal models of collective action.
With the negative sign for $\sqrt m_s$, the quarks strange, charm and bottom make a Koide tuple. It continues the c-b-t tuple previously found by Rodejohann and Zhang and, more peculiar, it is quasi-orthogonal to the original lepton triplet.
Social media have provided plentiful evidence of their capacity for information diffusion. Fads and rumors, but also social unrest and riots travel fast and affect large fractions of the population participating in online social networks (OSNs). This has spurred much research regarding the mechanisms that underlie social contagion, and also who (if any) can unleash system-wide information dissemination. Access to real data, both regarding topology --the network of friendships-- and dynamics --the actual way in which OSNs users interact--, is crucial to decipher how the former facilitates the latter's success, understood as efficiency in information spreading. With the quantitative analysis that stems from complex network theory, we discuss who (and why) has privileged spreading capabilities when it comes to information diffusion. This is done considering the evolution of an episode of political protest which took place in Spain, spanning one month in 2011.
The number of people using online social networks in their everyday life is continuously growing at a pace never saw before. This new kind of communication has an enormous impact on opinions, cultural trends, information spreading and even in the commercial success of new products. More importantly, social online networks have revealed as a fundamental organizing mechanism in recent country-wide social movements. In this paper, we provide a quantitative analysis of the structural and dynamical patterns emerging from the activity of an online social network around the ongoing May 15th (15M) movement in Spain. Our network is made up by users that exchanged tweets in a time period of one month, which includes the birth and stabilization of the 15M movement. We characterize in depth the growth of such dynamical network and find that it is scale-free with communities at the mesoscale. We also find that its dynamics exhibits typical features of critical systems such as robustness and power-law distributions for several quantities. Remarkably, we report that the patterns characterizing the spreading dynamics are asymmetric, giving rise to a clear distinction between information sources and sinks. Our study represent a first step towards the use of data from online social media to comprehend modern societal dynamics.
We consider Koide's equation for charged leptons jointly with hypotheses implied in the ancient Dual Quark-Gluon model. The focus is to motivate the possibility of a supersymmetric framework akin to the one of D=11 maximal supergravity.
We suggest a very simple but general operator to break mass degeneration between representations of the Poincare group having spin 1 and 1/2. A quantity very similar, at experimental 0.13 $σ$ level, to Weinberg's angle, appears during the process.
Asking very elementary relativistic quantum mechanics to meet quantums of area and time, it is possible to observe at a general level: a) the seesaw bound for the mass of neutrinos, and b) the need of a gauge group at energies below Planck mass.
We revisit Sakurai's remark on the regularities of lepton-pair widths for mesons, extending the panorama to radiative $X \to γγ$ and total decays. The regularities persist, and somehow surprisingly some of them seem to relate with Fermi's constant -or $Z^0$-.
We note that hadronic susy (empirical quark-diquark) symmetry can be expanded into the lepton sector, and that for three generations the counting of degrees of freedom is the one we need to build charged supermultiplets. For this to cure hierarchy, Higgs modeling becomes restricted.
The GUT value of Weinberg's angle is also the value that minimises the total square matrix elements of $Z^0$ decay, independently of any GUT consideration, and thus the one that maximises the neutrino branching ratio against total width. We review the proof of this result and some related facts.
We inquire if the total decay rate of neutral vector mesons can contain relevant off-shell contributions from the triangle anomaly. The answer seems to be affirmative for the case of J/Psi, and as a byproduct we get estimates of the decay width for neutral pions.
We present a short historical and bibliographical review of the lepton mass formula of Yoshio Koide, as well as some speculations on its extensions to quark and neutrino masses, and its possible relations to more recent theoretical developments.
Assuming a minimum value for area measurement, the emergence of quantum mechanics can be easily motivated from naive consideration of gravitational force. Here we provide some pedagogical examples and extensions. At the same time, the role of Planck mass is shown to be of some theoretical influence even at low energies.
We present a fit to the experimental charged lepton masses as coming from radiative corrections in QED.