Social media play a pivotal role in shaping citizens political opinion. According to the Euro-barometer, the percentage of EU citizens employing online social networks to access information, on a daily basis, has increased from 18% in 2010 to 42% in 2017. The tight entwinement between social media and the unfolding of political dynamics has motivated the interest of researchers for the analysis of users online behavior - with particular emphasis on topics like group polarization during debates and echo-chambers formation - to unveil the modes and the implications of online interactions for political processes. In this context, where attention has gone predominantly towards the study of online relations between users, semantic aspects have remained under-explored. In the present paper, we aim at filling this gap by, first, identifying the discursive communities that animate the political debate in the run up of the 2018 Italian Elections and, then, studying the semantic mechanisms that shape their internal Twitter discussions. We do so by monitoring, on a daily basis, the structural evolution of the corresponding semantic networks. As our analysis points out, the supporters of the political alliances present at the elections are characterized by a markedly different online behavior, in turn inducing semantic networks with different topological structures. The supporters of the right-wing parties alliance display a particularly active behavior condensed in a single, densely connected cluster wherein discussions take place in conjunction with mediated events such as political talk shows. Daily semantic networks triggered by the users retweeting members of the 5 Star Movement (M5S) tend, instead, to be less centralized suggesting a "more distributed" way of discussing a variety of themes, e.g. those raised as central by this new incumbent in the Italian political scenario.

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分析 Twitter 语义网络：以 2018 年意大利大选为例

社交媒体在塑造公民政治观点方面发挥着关键作用。根据欧洲晴雨表，欧盟公民每天使用在线社交网络获取信息的百分比从 2010 年的 18% 增加到 2017 年的 42%。社交媒体与政治动态之间的紧密联系激发了研究人员对用户在线行为分析的兴趣——特别强调辩论期间的群体极化和回声室形成等主题——揭示在线互动对政治进程的模式和影响。在这种情况下，注意力主要集中在研究用户之间的在线关系上，语义方面仍未得到充分探索。在本文中，我们的目标是通过以下方式填补这一空白：确定在 2018 年意大利大选之前引发政治辩论的话语社区，然后研究塑造其内部 Twitter 讨论的语义机制。我们通过每天监控相应语义网络的结构演变来做到这一点。正如我们的分析所指出的那样，参加选举的政治联盟的支持者的特点是明显不同的在线行为，进而诱导出具有不同拓扑结构的语义网络。右翼政党联盟的支持者表现出一种特别活跃的行为，它们集中在一个紧密相连的集群中，其中讨论与政治脱口秀等中介事件一起进行。