# Posts

14 December / /

## How to Organize your Deep Reinforcement Learning Agents: The Importance of Communication Topology

Authors: Dhaval Adjodah, Dan Calacci, Abhimanyu Dubey, Peter Krafft, Esteban Moro, Alex `Sandy’ Pentland Journal: Preprint (2018). arXiv Abstract: In this empirical paper, we investigate how learning agents can be arranged in more efficient communication topologies for improved learning. This is an important problem because a common technique to improve speed and robustness of learning in deep reinforcement learning and many other machine learning algorithms is to run multiple learning agents in parallel.
07 November / /

## ScamCoins, S*** Posters, and the Search for the Next Bitcoin(TM): Collective Sensemaking in Cryptocurrency Discussions

Authors: Eaman Jahani, Peter M. Krafft, Yoshihiko Suhara, Esteban Moro, Alex “Sandy” Pentland Journal: Proc. ACM Hum.-Comput. Interact. 2, CSCW, Article 79 (November 2018), 28 pages. LINK Abstract: Participants in cryptocurrency markets are in constant communication with each other about the latest coins and news releases. Do these conversations build hype through the contagiousness of excitement, help the community process information, or play some other role? Using a novel dataset from a major cryptocurrency forum, we conduct an exploratory study of the characteristics of online discussion around cryptocurrencies.
01 September / /

## Attack Tolerance of Link Prediction Algorithms: How to Hide Your Relations in a Social Network

Authors: Marcin Waniek, Kai Zhou, Yevgeniy Vorobeychik, Esteban Moro, Tomasz P Michalak, Talal Rahwan Journal: Preprint (2018). arXiv Abstract: Link prediction is one of the fundamental research problems in network analysis. Intuitively, it involves identifying the edges that are most likely to be added to a given network, or the edges that appear to be missing from the network when in fact they are present. Various algorithms have been proposed to solve this problem over the past decades.
19 June / /

Authors: David Garcia, Yonas Mitike Kassa, Angel Cuevas, Manuel Cebrian, Esteban Moro, Iyad Rahwan, and Ruben Cuevas Journal: PNAS June 19, 2018. 201717781. LINK Abstract: Online social media are information resources that can have a transformative power in society. While the Web was envisioned as an equalizing force that allows everyone to access information, the digital divide prevents large amounts of people from being present online. Online social media, in particular, are prone to gen- der inequality, an important issue given the link between social media use and employment.
28 April / /

## Weather impacts expressed sentiment

Authors: Patrick Baylis, Nick Obradovich, Yury Kryvasheyeu, Haohui Chen, Lorenzo Coviello, Esteban Moro, Manuel Cebrian, James H. Fowler Journal: PLoS ONE 13(4): e0195750 (2018) LINK Abstract: We conduct the largest ever investigation into the relationship between meteorological con- ditions and the sentiment of human expressions. To do this, we employ over three and a half billion social media posts from tens of millions of individuals from both Facebook and Twitter between 2009 and 2016.
24 April / /

## MemeSequencer: Sparse Matching for Embedding Image Macros

Authors: Abhimanyu Dubey, Esteban Moro, Manuel Cebrian, Iyad Rahwan Journal: WWW’18 Proceedings of the Web Conference 2018 LINK Abstract: The analysis of the creation, mutation, and propagation of social media content on the Internet is an essential problem in computational social science, affecting areas ranging from marketing to political mobilization. A first step towards understanding the evolution of images online is the analysis of rapidly modifying and propagating memetic imagery or ‘memes’.
28 June / /

## Temporal patterns behind the strength of persistent ties

Authors: Henry Navarro, Giovanna Miritello, Arturo Canales, Esteban Moro Journal: EPJ Data Science (2017) 6:31 LINK Abstract: Social networks are made out of strong and weak ties having very different structural and dynamical properties. But what features of human interaction build a strong tie? Here we approach this question from a practical way by finding what are the properties of social interactions that make ties more persistent and thus stronger to maintain social interactions in the future.
07 March / /

## Twitter Session Analytics: Profiling Users’ Short-Term Behavioral Changes

Authors: Farshad Kooti, Esteban Moro, and Kristina Lerman Journal: Proceedings of SocInfo 2016 LINK Abstract: Human behavior shows strong daily, weekly, and monthly patterns. In this work, we demonstrate online behavioral changes that occur on a much smaller time scale: minutes, rather than days or weeks. Specifically, we study how people distribute their effort over different tasks during periods of activity on the Twitter social platform. We demonstrate that later in a session on Twitter, people prefer to per- form simpler tasks, such as replying and retweeting others’ posts, rather than composing original messages, and they also tend to post shorter messages.
14 March / /

## Fully nonlinear dynamics of stochastic thin-film dewetting

Authors: S. Nesic, R. Cuerno, E. Moro, and L. Kondic Journal: Physical Review E 92, 061002(R) LINK | PDF Abstract: The spontaneous formation of droplets via dewetting of a thin fluid film from a solid substrate allows materials nanostructuring. Often, it is crucial to be able to control the evolution, and to produce patterns characterized by regularly spaced droplets. While thermal fluctuations are expected to play a role in the dewetting process, their relevance has remained poorly understood, particularly during the nonlinear stages of evolution that involve droplet formation.
14 March / /

## Rapid assessment of disaster damage using social media activity

Authors: Yury Kryvasheyeu1, Haohui Chen, Nick Obradovich, Esteban Moro, Pascal Van Hentenryck, James Fowler and Manuel Cebrian Journal: Science Advances 11 Mar 2016: Vol. 2, no. 3, e1500779 (2016) LINK Abstract: Could social media data aid in disaster response and damage assessment? Countries face both an increasing frequency and an increasing intensity of natural disasters resulting from climate change. During such events, citizens turn to social media platforms for disaster-related communication and information.
13 October / /

## Daily rhythms in mobile telephone communication

Authors:Talayeh Aledavood , Eduardo López, Sam G. B. Roberts, Felix Reed-Tsochas, Esteban Moro, Robin I. M. Dunbar, Jari Saramäki Journal: PLoS ONE 10(9), e0138098 (2015) LINK Abstract: Circadian rhythms are known to be important drivers of human activity and the recent availability of electronic records of human behaviour has provided fine-grained data of temporal patterns of activity on a large scale. Further, questionnaire studies have identified important individual differences in circadian rhythms, with people broadly categorised into morning-like or evening-like individuals.
07 May / /

## From Seconds to Months: multi-scale dynamics of mobile telephone calls

Authors:Jari Saramaki, Esteban Moro Journal: Eur. Phys. J. B (2015) 88: 164 LINK | **arXiv Abstract: Big Data on electronic records of social interactions allow approaching human behaviour and sociality from a quantitative point of view with unforeseen statistical power. Mobile telephone Call Detail Records (CDRs), automatically collected by telecom operators for billing purposes, have proven especially fruitful for understanding one-to-one communication patterns as well as the dynamics of social networks that are reflected in such patterns.
07 May / /

## Social media fingerprints of unemployment

Authors:Alejandro Llorente, Manuel García-Herránz, Manuel Cebrián and Esteban Moro Journal: PLoS ONE 10(5): e0128692 (2014) LINK Summary: Publicly available social media data can be used to quantify deviations from typical patterns of behavior and uncover how these deviations signal the socio-economical status of regions. Using data from geolocalized Twitter messages, we find that unemployment is correlated with technology adoption, daily activity, diversity in mobility patterns and correctness in communication style.
03 November / /

## Macroscopic Response to Microscopic Intrinsic Noise in Three-Dimensional Fisher Fronts

Authors:Svetozar Nesic, Rodolfo Cuerno, and Esteban Moro Journal: Physical Review Letters 113, 180602 (2014) LINK Summary We study the dynamics of three-dimensional Fisher fronts in the presence of density fluctuations. To this end we simulate the Fisher equation subject to stochastic internal noise, and study how the front moves and roughens as a function of the number of particles in the system, N. Our results suggest that the macroscopic behaviour of the system is driven by the microscopic dynamics at its leading edge where number fluctuations are dominated by rare events.
22 April / /

## Comunidades de partidarios en redes sociales: estudio de las elecciones catalanas de 2010 y 2012

Authors: Esteban Moro Book: Cotarelo, R. & Olmeda, J.A. (Comps.) (forthcoming). La democracia del siglo XXI. Política, medios de comunicación, internet y redes sociales. Actas de las II Jornadas españolas de ciberpolítica, 28 de mayo de 2013. Madrid: Centro de Estudios Políticos y Constitucionales. [pdf] Abstract: En los últimos años hemos asistido a un incremento notable de eventos de carácter político y/o social que han sido promovidos (cuando no originados) a través de medios de comunicación electrónicos.
09 April / /

## Using Friends as Sensors to Detect Global-Scale Contagious Outbreaks

Authors: Manuel Garcia-Herranz, Esteban Moro, Manuel Cebrian, Nicholas A. Christakis and James H. Fowler Journal: PLoS ONE 9(4): e92413 (2014) LINK SummaryRecent research has focused on the monitoring of global–scale online data for improved detection of epidemics, mood patterns, movements in the stock market political revolutions, box-office revenues, consumer behaviour and many other important phenomena. However, privacy considerations and the sheer scale of data available online are quickly making global monitoring infeasible, and existing methods do not take full advantage of local network structure to identify key nodes for monitoring.
13 February / /

## Performance of Social Network Sensors During Hurricane Sandy

Authors: Yury Kryvasheyeu, Haohui Chen, Esteban Moro, Pascal Van Hentenryck, Manuel Cebrian Journal: PLoS ONE 10(2): e0117288 (2015) LINK Summary Information flow during catastrophic events is a critical aspect of disaster management. Modern communication platforms, in particular online social networks, provide an opportunity to study such flow, and a mean to derive early-warning sensors, improving emergency preparedness and response. Performance of the social networks sensor method, based on topological and behavioural properties derived from the “friendship paradox”, is studied here for over 50 million Twitter messages posted before, during, and after Hurricane Sandy.
17 May / /

## Time allocation in social networks: correlation between social structure and human communication dynamics

Authors: Giovanna Miritello, Rubén Lara, and Esteban Moro Book: “Temporal Networks”, Springer, 2013. Series: Understanding Complex Systems. Holme, Petter; Saramaki, Jari (Eds.) **[PDF]((http://arxiv.org/pdf/1305.3865v1.pdf)** Summary Recent research has shown the deep impact of the dynamics of human interactions (or temporal social networks) on the spreading of information, opinion formation, etc. In general, the bursty nature of human interactions lowers the interaction between people to the extent that both the speed and reach of information diffusion are diminished.
18 April / /

## The predictability of consumer visitation patterns

Authors: Coco Krumme, Alejandro Llorente, Manuel Cebrian, Alex (“Sandy”) Pentland & Esteban Moro Journal: Sci. Rep. 3, 1645; (2013). LINK Abstract: We consider hundreds of thousands of individual economic transactions to ask: how predictable are consumers in their merchant visitation patterns? Our results suggest that, in the long-run, much of our seemingly elective activity is actually highly predictable. Notwithstanding a wide range of individual preferences, shoppers share regularities in how they visit merchant locations over time.
09 April / /

## Limited communication capacity unveils strategies for human interaction

Authors: Giovanna Miritello, Rubén Lara, Manuel Cebrián and Esteban Moro Journal: Scientific Reports 3, 1950 (2013). LINK Abstract: Social connectivity is the key process that characterizes the structural properties of social networks and in turn processes such as navigation, influence or information diffusion. Since time, attention and cognition are inelastic resources, humans should have a predefined strategy to manage their social interactions over time. However, the limited observational length of existing human interaction datasets, together with the bursty nature of dyadic communications have hampered the observation of tie dynamics in social networks.
01 April / /

## Limits of social mobilization

Authors: Alex Rutherford, Manuel Cebrian, Sohan Dsouza, Esteban Moro, Alex Pentland, and Iyad Rahwan Journal: PNAS 110 (16), 6281-6286 (2013) LINK Abstract: The Internet and social media have enabled the mobilization of large crowds to achieve time-critical feats, ranging from mapping crises in real time, to organizing mass rallies, to conducting search-and-rescue operations over large geographies. Despite significant success, selection bias may lead to inflated expectations of the efficacy of social mobilization for these tasks.
14 January / /

## Time as a limited resource: Communication Strategy in Mobile Phone Networks

Authors: Giovanna Miritello, Esteban Moro, Rubén Lara, Rocío Martínez-López, Sam G. B. Roberts, Robin I. M. Dunbar Journal: Social Networks 35, 89 (2013) LINK | arXiv Abstract: We used a large database of 9 billion calls from 20 million mobile users to examine the relationships between aggregated time spent on the phone, personal network size, tiestrength and the way in which users distributed their limited time across their network (disparity).
12 September / /

## Predicting Human Preferences Using the Block Structure of Complex Social Networks

Authors: Roger Guimerà, Alejandro Llorente, Esteban Moro y Marta Sales-Pardo Journal: PLoS ONE 7, e44620 (2012) LINK Abstract: With ever-increasing available data, predicting individuals’ preferences and helping them locate the most relevant information has become a pressing need. Understanding and predicting preferences is also important from a fundamental point of view, as part of what has been called a “new” computational social science. Here, we propose a novel approach based on stochastic block models, which have been developed by sociologists as plausible models of complex networks of social interactions.
12 March / /

## Agent-specific impact of single trades in financial markets

Authors: Alex Bladon, Esteban Moro y Tobias Galla Journal: Physical Review E 85, 036103 (2012) LINK | arXiv Abstract: We present an analysis of the price impact associated with single trades effected by different financial firms. Using data from the Spanish Stock Market, we find a high degree of heterogeneity across different market members, both in the instantaneous impact functions and in the time-dependent market response to trades by individual members.
03 November / /

## Branching dynamics of viral information spreading

Authors: José Luis Iribarren and Esteban Moro Journal: Physical Review E 84, 046116 (2011) LINK | arXiv Abstract: Despite its importance for rumors or innovations propagation, peer-to-peer collaboration, social networking, or marketing, the dynamics of information spreading is not well understood. Since the diffusion depends on the heterogeneous patterns of human behavior and is driven by the participants’ decisions, its propagation dynamics shows surprising properties not explained by traditional epidemic or contagion models.
21 July / /

## Social Features of Online Networks: The Strength of Intermediary Ties in Online Social Media

Authors: P. A. Grabowicz, J. J. Ramasco, E. Moro, J. P. Pujol and V. M. Eguiluz Journal: PLoS ONE 7(1): e29358 (2012). LINK Abstract: An increasing fraction of today’s social interactions occur using online social media as communication channels. Recent worldwide events, such as social movements in Spain or revolts in the Middle East, highlight their capacity to boost people’s coordination. Online networks display in general a rich internal structure where users can choose among different types and intensity of interactions.
17 June / /

## Twitter y Política: Información, Opinión y ¿Predicción?

Authors: M. Luz Congosto, Montse Fernández y Esteban Moro Journal: Cuadernos de Comunicación Evoca 4 (2011). LINK Abstract: Estamos a las puertas de una nueva manera de medir la opinión política: mediante la conversación en Red, que permite no sólo conocer el feedback de los ciudadanos a la política, sino también la imagen de los políticos que se refleja en la Red, la dinámica de opinión en comunidades o grupos y el efecto de los diferentes medios de comunicación en dicha conversación.
08 February / /

## Affinity Paths and information diffusion in social networks

Authors: José Luis Iribarren and Esteban Moro Journal: Social Networks 33, 134-142 (2011). LINK | arXiv Abstract: 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 contents. 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.
25 November / /

## Dynamical strength of social ties in information spreading

Authors: Giovanna Miritello, Esteban Moro y Rubén Lara Journal: Physical Review E (Rapid Comm) 83, 045102 (2011). LINK | arXiv Abstract: We investigate the temporal patterns of human communication and its influence on the spreading of information in social networks. The analysis of mobile phone calls of 20 million people in one country shows that human communication is bursty and happens in group conversations. These features have opposite effects in information reach: while bursts hinder propagation at large scales, conversations favor local rapid cascades.
04 August / /

## Market impact and trading profile of large trading orders in stock markets

Authors: Esteban Moro, Javier Vicente, Luis G. Moyano, Austin Gerig, J. Doyne Farmer, Gabriella Vaglica, Fabrizio Lillo and Rosario N. Mantegna Journal: Phys. Rev. E 80, 066102 (2009) LINK | arXiv Abstract: We empirically study the market impact of trading orders. We are speciﬁcally interested in large trading orders that are executed incrementally, which we call hidden orders. These are reconstructed based on information about market member codes using data from the Spanish Stock Market and the London Stock Exchange.
04 August / /

## Impact of Human Activity Patterns on the Dynamics of Information Diffusion

Authors: J. L. Iribarren and E. Moro Journal: Physical Review Letters 103, 038702 (2009) LINK arXiv Abstract: We study the impact of human activity patterns on information diffusion. To this end we ran a viral email experiment involving 31183 individuals in which we were able to track a speciﬁc piece of information through the social network. We found that, contrary to traditional models, information travels at an unexpectedly slow pace.
04 July / /

## Specialization of strategies and herding behavior of trading firms in a financial market

Authors: Fabrizio Lillo, Esteban Moro, Gabriella Vaglica y Rosario Mantegna Journal: New Journal of Physics 10 (2008) 043019 LINK arXiv Abstract: Agent-based models of ﬁnancial markets usually make assumptions about agent’s preferred stylized strategies. Empirical validations of these assumptions have not been performed so far on a full-market scale. Here we present a comprehensive study of the resulting strategies followed by the ﬁrms which are members of the Spanish Stock Exchange.
06 June / /

## Information diffusion epidemics in social networks

Authors: José Luis Iribarren, Esteban Moro Journal: Preprint 0706.0641 arXiv Abstract: The dynamics of information dissemination in social networks is of paramount importance in processes such as rumors or fads propagation, spread of product innovations or “word-of-mouth” communications. Due to the difficulty in tracking a specific information when it is transmitted by people, most understanding of information spreading in social networks comes from models or indirect measurements. Here we present an integrated experimental and theoretical framework to understand and quantitatively predict how and when information spreads over social networks.
20 April / /

## Scaling laws of strategic behavior and size heterogeneity in agent dynamics

Authors: Gabriella Vaglica, Fabrizio Lillo, Esteban Moro y Rosario N. Mantegna Journal: Physical Review E 77, 036110 (2008). LINK | arXiv Abstract: The dynamics of many socioeconomic systems is determined by the decision making process of agents. The decision process depends on agent’s characteristics, such as preferences, risk aversion, behavioral biases, etc. In addition, in some systems the size of agents can be highly heterogeneous leading to very different impacts of agents on the system dynamics.
09 February / /

## Spreading of Viscous Fluid Drops on a Solid Substrate Assisted by Thermal Fluctuations

Authors: Benny Davidovitch, Esteban Moro, and Howard A. Stone Journal: Physical Review Letters 95, 244505 (2005). LINK Abstract: We study the spreading of viscous drops on a solid substrate, taking into account the effects of thermal fluctuations in the fluid momentum. A nonlinear stochastic lubrication equation is derived and studied using numerical simulations and scaling analysis. We show that asymptotically spreading drops admit self-similar shapes, whose average radii can increase at rates much faster than these predicted by Tanner’s law.
01 August / /

## Boundary preserving semi-analytical numerical algorithms for stochastic differential equations

Authors: Esteban Moro and Henri Schurz Journal: SIAM Journal of Scientific Computing, Volume 29 Issue 4, Pages 1525-1549 (2007). LINK | arXiv Abstract: Construction of splitting-step methods and properties of related non-negativity andboundary preserving numerical algorithms for solving stochastic differential equations (SDEs) of Ito-type are discussed. We present convergence proofs for a newly designed splitting-step algorithm and simulation studies for numerous numerical examples ranging from stochastic dynamics occurring in asset pricing theory in mathematical finance (SDEs of CIR and CEV models) to measure-valued diffusion and superBrownian motion (SPDEs) as met in biology and physics.
23 October / /

## Numerical schemes for continuum models of reaction-diffusion systems subject to internal noise

Authors: Esteban Moro Journal: Physical Review E (Rapid Communication) 70, 045102 (2004). LINK | arXiv Abstract: We present numerical schemes to integrate stochastic partial differential equations which describe the spatiotemporal dynamics of reaction-diffusion problems under the effect of internal fluctuations. The schemes conserve the non-negativity of the solutions and incorporate the Poissonian nature of internal fluctuations at small densities, their performance being limited by the level of approximation of density fluctuations at small scales.
31 August / /

## The Minority Game: an introductory guide

Authors: Esteban Moro Book: Advances in Condensed Matter and __Statistical Physics, _E. Korutcheva and R. Cuerno eds. (Nova Science Publishers, New York 2004). LINK | arXiv Abstract: The Minority Game is a simple model for the collective behavior of agents in an idealized situation where they have to compete through adaptation for a finite resource. This review summarizes the statistical mechanics community efforts to clear up and understand the behavior of this model.
01 June / /

## Hybrid method for simulating front propagation in reaction-diffusion systems

Authors: Esteban Moro Journal: Physical Review E, Rapid Communication 69, 060101 (2004). LINK | arXiv Abstract: We study the propagation of pulled fronts in the $$A\leftrightarrow A+A$$ microscopic reaction-diffusion process using Monte Carlo simulations. In the mean field approximation the process is described by the deterministic Fisher-Kolmogorov-Petrovsky-Piscounov equation. In particular, we concentrate on the corrections to the deterministic behavior due to the number of particles per correlated volume $$\Omega$$. By means of a hybrid simulation scheme, we manage to reach large macroscopic values of $$\Omega$$, which allows us to show the importance in the dynamics of microscopic pulled fronts of the interplay of microscopic fluctuations and their macroscopic relaxation.
25 August / /

## Emergence of pulled fronts in fermionic microscopic particle models

Authors: Esteban Moro Phys. Rev. E, Rapid Communication, 68, 025102 (2003). LINK | arXiv Abstract: We study the emergence and dynamics of pulled fronts described by the Fisher-Kolmogorov-Petrovsky-Piscounov (FKPP) equation in the microscopic reaction-diffusion process $$A\leftrightarrow A+A$$ on the lattice when only a particle is allowed per site. To this end we identify the parameter that controls the strength of internal fluctuations in this model, namely, the number of particles per correlated volume.
11 March / /

## Defect formation in the Swift-Hohenberg equation

Authors: Tobias Galla and Esteban Moro Journal: Phys. Rev. E, Rapid Communication 67, 035101 (2003). LINK | arXiv Abstract: We study numerically and analytically the dynamics of defect formation during a finite-time quench of the two-dimensional Swift-Hohenberg (SH) model of Rayleigh-Bénard convection. We find that the Kibble-Zurek picture of defect formation can be applied to describe the density of defects produced during the quench. Our study reveals the relevance of two factors: the effect of local variations of the striped patterns within defect-free domains and the presence of both pointlike and extended defects.
14 November / /

## Internal Fluctuations Effects on Fisher Waves

Authors: Esteban Moro Journal: Physical Review Letters 87, 238303 (2001) LINK | arXiv Abstract: We study the diffusion-limited reaction $$A \leftrightarrow A = A$$ in various spatial dimensions to observe the effect of internal fluctuations on the interface between stable and unstable phases. We find that, similar to what has been observed in d = 1 dimensions, internal fluctuations modify the mean-field predictions for this process, which is given by Fisher’s reaction-diffusion equation.