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Browsing by Subject "graphs"

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  • Analysing Controversy on Twitter via Graph Embeddings 
    Comănescu, Andrei-Daniel (2020)
    Social networks represent a public forum of discussion for various topics, some of them controversial. Twitter is such a social network; it acts as a public space where discourse occurs. In recent years the role of social networks in information spreading has increased. As have the fears regarding the increasingly polarised discourse on social networks, caused by the tendency of users to avoid exposure to opposing opinions, while increasingly interacting with only like-minded individuals. This work looks at controversial topics on Twitter, over a long period of time, through the prism of political polarisation. We use the daily interactions, and the underlying structure of the whole conversation, to create daily graphs that are then used to obtain daily graph embeddings. We estimate the political ideologies of the users that are represented in the graph embeddings. By using the political ideologies of users and the daily graph embeddings, we offer a series of methods that allow us to detect and analyse changes in the political polarisation of the conversation. This enables us to conclude that, during our analysed time period, the overall polarisation levels for our examined controversial topics have stagnated. We also explore the effects of topic-related controversial events on the conversation, thus revealing their short-term effect on the conversation as a whole. Additionally, the linkage between increased interest in a topic and the increase of political polarisation is explored. Our findings reveal that as the interest in the controversial topic increases, so does the political polarisation.
  • Safe walks for flow decompositions with subpath constraints, in general graphs 
    Ingervo, Eliel (2024)
    The problem of safety in a general graph is the problem of finding walks in the graph that are subwalks of a walk in any possible solution within a given model (Tomescu and Medvedev, 2017). The problem of safety has proven to be a valuable problem for bioinformatics in the context of genome assembly and other assembly problems. When working with perfect data, safe walks in a graph correspond to correct sequences of the genome. When working with real (erroneous) data, safe walks correspond to close to correct sequences, where the errors correspond only to errors already in the data. Safety has previously been considered in two different models: in a model where the graph holds only the information of graph topology, and in a model where the graph holds the information of graph topology and network flow. Subpath constraints are paths in a graph that restrict the solution set. Restricting a solution set increases the lengths of safe walks, so using a model that holds the information of subpath constraints is advantageous. However, subpath constraints have never been considered with the problem of safety. In this work, we introduce subwalk constraints, which are subpath constraints that can have cycles and are not limited to directed acyclic graphs (DAGs). Then, we present a new model, where the graph holds the information of graph topology, network flow and subwalk constraints. In the new model, we present three methodologies to compute safe walks that become possible because of subwalk constraints. Then, we present an algorithm that computes safe walks in polynomial time in the new model utilizing the three new methodologies. Due to the new model, all safe walks produced by other algorithms are subwalks of the safe walks generated by our new algorithm

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