Optimal strategies for a game on amenable semigroups

The semigroup game is a two-person zero-sum game defined on a semigroup S as follows: Players 1 and 2 choose elements x and y in S, respectively, and player 1 receives a payoff f(xy) defined by a function f from S to [-1,1]. If the semigroup is amenable in the sense of Day and von Neumann, one can extend the set of classical strategies, namely countably additive probability measures on S, to include some finitely additive measures in a natural way. This extended game has a value and the players have optimal strategies. This theorem extends previous results for the multiplication game on a compact group or on the positive integers with a specific payoff. We also prove that the procedure of extending the set of allowed strategies preserves classical solutions: if a semigroup game has a classical solution, this solution solves also the extended game.Comment: 17 pages. To appear in International Journal of Game Theor

National identity predicts public health support during a global pandemic

Understanding collective behaviour is an important aspect of managing the pandemic response. Here the authors show in a large global study that participants that reported identifying more strongly with their nation reported greater engagement in public health behaviours and support for public health policies in the context of the pandemic.Changing collective behaviour and supporting non-pharmaceutical interventions is an important component in mitigating virus transmission during a pandemic. In a large international collaboration (Study 1, N = 49,968 across 67 countries), we investigated self-reported factors associated with public health behaviours (e.g., spatial distancing and stricter hygiene) and endorsed public policy interventions (e.g., closing bars and restaurants) during the early stage of the COVID-19 pandemic (April-May 2020). Respondents who reported identifying more strongly with their nation consistently reported greater engagement in public health behaviours and support for public health policies. Results were similar for representative and non-representative national samples. Study 2 (N = 42 countries) conceptually replicated the central finding using aggregate indices of national identity (obtained using the World Values Survey) and a measure of actual behaviour change during the pandemic (obtained from Google mobility reports). Higher levels of national identification prior to the pandemic predicted lower mobility during the early stage of the pandemic (r = -0.40). We discuss the potential implications of links between national identity, leadership, and public health for managing COVID-19 and future pandemics

O mito do herói: uma análise a partir do discurso da Folha de S.Paulo acerca do caso Ronaldo na Copa do Brasil de 2009

This article's purpose is to analyze and discuss how the newspaper Folha de S. Paulo portrayed Ronaldo's image in articles published during the contest and after winning 2009 Brazil's Cup. Methodologically, this study is characterized as a historical research guided by the procedures of the history of the present time. The analysis material was constituted by the Folha de S. Paulo newspaper's sports section. We note that the paper elaborates its discourse through a protagonist role implicit in the athlete's history of achievements and failures, demonstrating Ronaldo as an established subject in the sports field and associating his image to a model for social representation.O objetivo deste artigo consiste em analisar e discutir como o jornal Folha de S. Paulo retratou a imagem de Ronaldo nas matérias publicadas durante a disputa e após a conquista da Copa do Brasil de 2009. Metodologicamente, o presente estudo é caracterizado como uma pesquisa histórica, pautada pelos procedimentos da história do tempo presente e o material de análise foi constituído pelo caderno de esportes da Folha de S. Paulo. Notamos que o jornal elabora o discurso através de um protagonismo implícito no histórico de conquistas e fracassos do atleta, demonstrando Ronaldo como um sujeito consolidado no campo esportivo e associando sua imagem como modelo de representação social