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X-WR-CALNAME:Namur Institute For Complex Systems
X-ORIGINAL-URL:https://www.naxys.be
X-WR-CALDESC:Events for Namur Institute For Complex Systems
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TZID:Europe/Paris
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DTSTART:20171029T010000
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DTSTART:20191027T010000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20180301T130000
DTEND;TZID=Europe/Paris:20180301T140000
DTSTAMP:20260408T154051
CREATED:20180131T211528Z
LAST-MODIFIED:20180213T140748Z
UID:312-1519909200-1519912800@www.naxys.be
SUMMARY:Alexandre Bovet (UNamur - UCL)
DESCRIPTION:Title: Opinion dynamics and fake versus traditional news influence in Twitter \nAbstract: We investigate the opinion of Twitter users during the 2016 US elections using a large scale dataset of more than 170 millions tweets. We develop a method to infer the opinion of Twitter users regarding the candidates by using a combination of natural language processing of the tweet contents\, machine learning classification and analysis of the hashtags co-occurrence network. We study the temporal social networks formed by the interactions among millions of Twitter users and infer the support of each user to the presidential candidates. The resulting Twitter opinion trend follows the New York Times National Polling Average\, which represents an aggregate of hundreds of independent traditional polls\, with remarkable accuracy.\nGoing beyond the daily opinion analysis and analyzing the level of activity\, the repartition of the supporters between the strongly connected giant component and the rest of the network and the daily fluctuations in the number of users reveal a clear dichotomy between the behavior of supporters of each candidate. Although Clinton supporters are the majority in Twitter\, Trump supporters are generally more active and more constant in their support\, while Clinton supporters are less active and show their support only occasionally.\nTo understand the role of information diffusion on Twitter opinion dynamics\, we consider tweets containing URLs directing to news outlet websites. In particular\, we compare websites known to diffuse fake news compared to traditional\, fact-based\, news outlets. We find that 29% of the tweets linking to news outlets points to websites containing fake or extremely biased news. Analyzing the information diffusion networks\, we find that user diffusing fake news form more connected and less heterogeneous networks than users in traditional news diffusion networks. While influencers of traditional news outlets are journalists and public figures with verified Twitter accounts\, most influencers of fake news and extremely biased websites are unknown users or users with deleted Twitter accounts. Finally\, an analysis of the activity dynamics of influencers reveals that influencers of tradition news are driving the most part of Twitter while fake news influencers are\, in fact\, mostly driven by the activity of Trump supporters.
URL:https://www.naxys.be/event/alexandre-bovet-unamur/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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DTSTART;TZID=Europe/Paris:20180308T130000
DTEND;TZID=Europe/Paris:20180308T140000
DTSTAMP:20260408T154051
CREATED:20180214T105809Z
LAST-MODIFIED:20181016T114613Z
UID:355-1520514000-1520517600@www.naxys.be
SUMMARY:Alexey Medvedev (UNamur)
DESCRIPTION:Title:   Modelling structure and predicting dynamics of discussion threads in online boards using Hawkes processesAbstract:  Online social platforms provide a fruitful source of information about social interaction. Depending on the platform\, various tree-like cascading patterns emerge as a consequence of such interaction. For example\, on Twitter or on Facebook people interact via resharing messages\, which turns into cascade trees of reshares\, in email networks people forward messages to their peers resulting in trees of email forwards\, in online boards like Digg or Reddit people interact via discussing particular posts\, which leaves a trace of discussion trees. The two main questions arise: what is the shape of these cascades and how to predict the dynamics of their evolution? The question of evolution of discussion threads is now gradually being understood. By now researchers studied only the structural evolution of discussion trees and the dynamical properties are left out of consideration. Nevertheless\, there was proposed a sort of a mean-field model for dynamics and structure\, however by the design the model has limited utility in practice. We consider cascades given by discussion trees of posts in online board Reddit. The dataset of Reddit discussion threads consists of all posts and comments submitted to Reddit from Jan\, 2008 till Jan\, 2015. The dataset in total contains more than 150 million posts and around 1.4 billion comments. We propose a model of discussion trees generation based on the self-exciting Hawkes processes\, which represents both the tree structure and temporal information. We use the dataset of Reddit discussion threads to show that structurally trees resemble Galton-Watson trees with a special root offspring distribution\, and distinct the cases when the dynamics of comments attraction can be well predicted using Hawkes processes.
URL:https://www.naxys.be/event/alexey-medvedev-unamur/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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DTSTART;TZID=Europe/Paris:20180329T130000
DTEND;TZID=Europe/Paris:20180329T140000
DTSTAMP:20260408T154051
CREATED:20180131T211858Z
LAST-MODIFIED:20180324T213728Z
UID:314-1522328400-1522332000@www.naxys.be
SUMMARY:Jean Teyssandier (Cornell University\, USA)
DESCRIPTION:Title: Orbital evolution during planet-⁠disc interactions \nAbstract: The origin and wide distribution of eccentricities and inclinations in planetary systems remains to be explained\, in particular in the context of planet-disc interactions. In this talk I will present a study of the evolution of eccentricity in discs and planets that combines methods from celestial mechanics and hydrodynamics\, and takes the form of a linear secular theory. I will compare the predictions of this linear theory against direct hydrodynamical simulations and show how eccentricity can grow. I will discuss what these results imply for the orbital structure of protoplanetary discs and young planetary systems. I will also discuss how moderate inclinations can be generated via similar mechanisms.
URL:https://www.naxys.be/event/jean-teyssandier-cornell-university-usa/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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