De retibus socialibus et legibus momenti

Online Social Networks (OSNs) are a cutting edge topic. Almost everybody --users, marketers, brands, companies, and researchers-- is approaching OSNs to better understand them and take advantage of their benefits. Maybe one of the key concepts underlying OSNs is that of influence which is highly related, although not entirely identical, to those of popularity and centrality. Influence is, according to Merriam-Webster, "the capacity of causing an effect in indirect or intangible ways". Hence, in the context of OSNs, it has been proposed to analyze the clicks received by promoted URLs in order to check for any positive correlation between the number of visits and different "influence" scores. Such an evaluation methodology is used in this paper to compare a number of those techniques with a new method firstly described here. That new method is a simple and rather elegant solution which tackles with influence in OSNs by applying a physical metaphor.Comment: Changes made for third revision: Brief description of the dataset employed added to Introduction. Minor changes to the description of preparation of the bit.ly datasets. Minor changes to the captions of Tables 1 and 3. Brief addition in the Conclusions section (future line of work added). Added references 16 and 18. Some typos and grammar polishe

Affinity Paths and Information Diffusion in Social Networks

Widespread interest in the diffusion of information through social networks has produced a large number of Social Dynamics models. A majority of them use theoretical hypothesis to explain their diffusion mechanisms while the few empirically based ones average out their measures over many messages of different content. Our empirical research tracking the step-by-step email propagation of an invariable viral marketing message delves into the content impact and has discovered new and striking features. The topology and dynamics of the propagation cascades display patterns not inherited from the email networks carrying the message. Their disconnected, low transitivity, tree-like cascades present positive correlation between their nodes probability to forward the message and the average number of neighbors they target and show increased participants' involvement as the propagation paths length grows. Such patterns not described before, nor replicated by any of the existing models of information diffusion, can be explained if participants make their pass-along decisions based uniquely on local knowledge of their network neighbors affinity with the message content. We prove the plausibility of such mechanism through a stylized, agent-based model that replicates the \emph{Affinity Paths} observed in real information diffusion cascades.Comment: 11 pages, 7 figure

Critical Market Crashes

This review is a partial synthesis of the book ``Why stock market crash'' (Princeton University Press, January 2003), which presents a general theory of financial crashes and of stock market instabilities that his co-workers and the author have developed over the past seven years. The study of the frequency distribution of drawdowns, or runs of successive losses shows that large financial crashes are ``outliers'': they form a class of their own as can be seen from their statistical signatures. If large financial crashes are ``outliers'', they are special and thus require a special explanation, a specific model, a theory of their own. In addition, their special properties may perhaps be used for their prediction. The main mechanisms leading to positive feedbacks, i.e., self-reinforcement, such as imitative behavior and herding between investors are reviewed with many references provided to the relevant literature outside the confine of Physics. Positive feedbacks provide the fuel for the development of speculative bubbles, preparing the instability for a major crash. We demonstrate several detailed mathematical models of speculative bubbles and crashes. The most important message is the discovery of robust and universal signatures of the approach to crashes. These precursory patterns have been documented for essentially all crashes on developed as well as emergent stock markets, on currency markets, on company stocks, and so on. The concept of an ``anti-bubble'' is also summarized, with two forward predictions on the Japanese stock market starting in 1999 and on the USA stock market still running. We conclude by presenting our view of the organization of financial markets.Comment: Latex 89 pages and 38 figures, in press in Physics Report

Accelerated modernity

This paper aims to show how current undergraduate students use social media in their daily lives, taking the first ten minutes of the day as a concentrated insight into their priorities of practice. The work draws on primary data from four focus groups of UK business students in higher education. Through the application of Rosa’s construct of social acceleration, initial findings indicate a hierarchy of priorities, shaped by economic, cultural and structural drivers in what social media is engaged with, in what sequence, and for what purpose. These choices reflect acceleration in the changes to the technology, the pace of social changes and the accelerated expectations of the pace of life. This article seeks to reimagine transmedia in the context of social media identity in an accelerated modernity. Here we have the intersection of three important rapidly changing constructs for the analysis of the use of media. These are the widespread, ubiquitous use of social media, the acceleration of late modernity and the impact of transmedia practice on how users engage with media

Do tablets cure the pedagogy headache?

Tablet devices have made a huge impact in schools and in 2015 they were predicted to outsell personal computers (Gartner, 2014). 70 per cent of UK schools are estimated to be using tablets (BBC, online) and across Europe, “laptops, tablets and net-books are becoming pervasive” (EU schoolnet, 2014). As these devices become established in schools they both support and develop existing practice (Burden, Hopkins, Male, Martin and Trala, 2012; Baran, 2014), but are also starting to challenge some existing models of thinking and pedagogy (Fullan and Langworth, 2014; Kearney, Schuck, Burden and Aubusson, 2012) and also teachers’ attitudes towards learning and teaching (Ertmer, 1999; Burden and Hopkins, 2015). In offering opportunities for learning to become more authentic, personal and collaborative (Kearney et al., 2012) there are opportunities for teachers to start to redesign the ways in which learning is taking place (Puentedura, 2010; McCormick and Scrimshaw, 2001). Traxler defines mobile learning as “an educational process, in which handheld devices or palmtops are the only or dominant used technology tools” (2007: 2) and Kearney et al. (2012) argue that it has the potential to revolutionise the learning process in allowing individuals to determine their own independent paradigms and frameworks of learning. These devices are also sophisticated producers of digital artefacts and children and teachers are capable of being co-producers of learning materials

Explaining the stellar initial mass function with the theory of spatial networks

The distributions of stars and prestellar cores by mass (initial and dense core mass functions, IMF/DCMF) are among the key factors regulating star formation and are the subject of detailed theoretical and observational studies. Results from numerical simulations of star formation qualitatively resemble an observed mass function, a scale-free power law with a sharp decline at low masses. However, most analytic IMF theories critically depend on the empirically chosen input spectrum of mass fluctuations which evolve into dense cores and, subsequently, stars, and on the scaling relation between the amplitude and mass of a fluctuation. Here we propose a new approach exploiting the techniques from the field of network science. We represent a system of dense cores accreting gas from the surrounding diffuse interstellar medium (ISM) as a spatial network growing by preferential attachment and assume that the ISM density has a self-similar fractal distribution following the Kolmogorov turbulence theory. We effectively combine gravoturbulent and competitive accretion approaches and predict the accretion rate to be proportional to the dense core mass: $dM/dt \propto M$. Then we describe the dense core growth and demonstrate that the power-law core mass function emerges independently of the initial distribution of density fluctuations by mass. Our model yields a power law solely defined by the fractal dimensionalities of the ISM and accreting gas. With a proper choice of the low-mass cut-off, it reproduces observations over three decades in mass. We also rule out a low-mass star dominated "bottom-heavy" IMF in a single star-forming region.Comment: 8 pages, 5 figures, v2 matches the published versio