1. Stability of cooperation under image scoring in group interactionsHeinrich H. Nax, Matjaž Perc, Attila Szolnoki, Dirk Helbing, 2015, izvirni znanstveni članek Opis: Image scoring sustains cooperation in the repeated two-player prisoner's dilemma through indirect reciprocity, even though defection is the uniquely dominant selfish behaviour in the one-shot game. Many real-world dilemma situations, however, firstly, take place in groups and, secondly, lack the necessary transparency to inform subjects reliably of others' individual past actions. Instead, there is revelation of information regarding groups, which allows for "group scoring" but not for image scoring. Here, we study how sensitive the positive results related to image scoring are to information based on group scoring. We combine analytic results and computer simulations to specify the conditions for the emergence of cooperation. We show that under pure group scoring, that is, under the complete absence of image-scoring information, cooperation is unsustainable. Away from this extreme case, however, the necessary degree of image scoring relative to group scoring depends on the population size and is generally very small. We thus conclude that the positive results based on image scoring apply to a much broader range of informational settings that are relevant in the real world than previously assumed.
Ključne besede: public goods, group interactions, phase transition, social dilemma, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 1143; Prenosov: 425
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2. A double-edged sword: benefits and pitfalls of heterogeneous punishment in evolutionary inspection gamesMatjaž Perc, Attila Szolnoki, 2015, izvirni znanstveni članek Opis: As a simple model for criminal behavior, the traditional two-strategy inspection game yields counterintuitive results that fail to describe empirical data. The latter shows that crime is often recurrent, and that crime rates do not respond linearly to mitigation attempts. A more apt model entails ordinary people who neither commit nor sanction crime as the third strategy besides the criminals and punishers. Since ordinary people free-ride on the sanctioning efforts of punishers, they may introduce cyclic dominance that enables the coexistence of all three competing strategies. In this setup ordinary individuals become the biggest impediment to crime abatement. We therefore also consider heterogeneous punisher strategies, which seek to reduce their investment into fighting crime in order to attain a more competitive payoff. We show that this diversity of punishment leads to an explosion of complexity in the system, where the benefits and pitfalls of criminal behavior are revealed in the most unexpected ways. Due to the raise and fall of different alliances no less than six consecutive phase transitions occur in dependence on solely the temptation to succumb to criminal behavior, leading the population from ordinary people-dominated across punisher-dominated to crime-dominated phases, yet always failing to abolish crime completely.
Ključne besede: crime, phase transition, social dilemma, physics of social systems
Objavljeno v DKUM: 23.06.2017; Ogledov: 732; Prenosov: 386
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3. Influence of temperature on the surface enhanced Raman scattering spectra of 2, 4, 6 - trinitrotolueneSimon Hamler, 2015, magistrsko delo Opis: The detection of trace amounts of explosive like trinitrotoluene (TNT) is an important issue in the prevention of terrorist attacks. Surface enhanced Raman scattering (SERS) spectroscopy has become a powerful detection technique for identification of minute amounts of analytes. This thesis presents data of TNT in solution, deposited on a nanostructured gold surface, which is heated up to 60 °C. The observed changes in the microscopy images and in the SERS spectra are explained by evaporation, phase transition and decomposition of the TNT molecules. The impact of temperature dependence of SERS effect is studied on a chemisorbed 4-Nitrothiophenol monolayer. To minimize the evaporation of TNT molecules, a self-assembled monolayer of mercaptohexanol (MCH) was inserted between plasmonic surface and TNT.
Ključne besede: surface enhanced Raman spectroscopy, explosives, temperature dependence, microscopy, evaporation, phase transition, decomposition
Objavljeno v DKUM: 05.11.2015; Ogledov: 1547; Prenosov: 81
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