The FGK formalism for black p-branes in d dimensions

We present a generalization to an arbitrary number of spacetime (d) and worldvolume (p+1) dimensions of the formalism proposed by Ferrara, Gibbons and Kallosh to study black holes (p=0) in d=4 dimensions. We include the special cases in which there can be dyonic and self- or anti-self-dual black branes. Most of the results valid for 4-dimensional black holes (relations between temperature, entropy and non-extremality parameter, and between entropy and black-hole potential on the horizon) are straightforwardly generalized. We apply the formalism to the case of black strings in N=2,d=5 supergravity coupled to vector multiplets, in which the black-string potential can be expressed in terms of the dual central charge and work out an explicit example with one vector multiplet, determining supersymmetric and non-supersymmetric attractors and constructing the non-extremal black-string solutions that interpolate between them.Comment: 28 pages no figures; v2: some references adde

Are groups more rational than individuals? A review of interactive decision making in groups

Many decisions are interactive; the outcome of one party depends not only on its decisions or on acts of nature but also on the decisions of others. In the present article, we review the literature on decision making made by groups of the past 25 years. Researchers have compared the strategic behavior of groups and individuals in many games: prisoner's dilemma, dictator, ultimatum, trust, centipede and principal-agent games, among others. Our review suggests that results are quite consistent in revealing that groups behave closer to the game-theoretical assumption of rationality and selfishness than individuals. We conclude by discussing future research avenues in this area

Gravitational collapse with tachyon field and barotropic fluid

A particular class of space-time, with a tachyon field, \phi, and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(\phi) \sim \phi^{-2}. Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, \gamma. Furthermore, these collapsing scenarios both have as final state the formation of a black hole.Comment: 18 pages, 7 figures. v3: minor changes. Final version to appear in GR

Lifshitz black holes in Brans-Dicke theory

We present an exact asymptotically Lifshitz black hole solution in Brans-Dicke theory of gravity in arbitrary $n(\ge 3)$ dimensions in presence of a power-law potential. In this solution, the dynamical exponent $z$ is determined in terms of the Brans-Dicke parameter $\omega$ and $n$. Asymptotic Lifshitz condition at infinity requires $z>1$, which corresponds to $-(n-1)/(n-2) \le \omega < -n/(n-1)$. On the other hand, the no-ghost condition for the scalar field in the Einstein frame requires $0<z \le 2(n-2)/(n-3)$. We compute the Hawking temperature of the black hole solution and discuss the problems encountered and the proposals in defining its thermodynamic properties. A generalized solution charged under the Maxwell field is also presented.Comment: 32 pages, no figure. v2: revised version. Section 3.1 and Appendix B improved. The argument in Appendix A clarified. v3: References added. v4: analysis on the black hole thermodynamical properties corrected. Final version to appear in JHE

An Agent-based Approach for Structured Modeling, Analysis and Improvement of Safety Culture

Safety culture is broadly recognized as important for operational safety in various fields, including air traffic management, power plant control and health care. Previous studies addressed characterization and assessment of safety culture extensively. Nevertheless, relations between safety culture and formal and informal organizational structures and processes are yet not well understood. To address this gap, a new, formal, agent-based approach is proposed. This paper shows the application of the approach to an air navigation service provider, including structured modeling, analysis and identification of improvement strategies for the organizational safety culture. The model results have been validated using safety culture data that had been achieved by an independent safety culture survey study. © 2011 The Author(s)

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges