We use the Tolman–Oppenheimer–Volkoff equations for a Chaplygin type fluid to study, analytically and numerically, the global behavior of static solutions of spherically symmetric objects. Two possible regimes are especially investigated. The first one is the phantom regime in which the pressure module exceeds the energy density. In this case the equator is absent and all the solutions have the geometry of a truncated spheroid with the same kind of singularity. The second case is the normal regime for which we (...) determine all the solutions, excluding the de Sitter one, corresponding to a tri-dimensional spheroidal geometry. Beyond the equator, three possible cases are considered; the first case has a closed spheroid characterized by a Schwarzschild-kind singularity with an infinite blue-shift at the south pole, the second case configuration has a regular spheroid and the third case has configuration of a truncated spheroid having a scalar curvature singularity to a finite value of the radial distance. We also compare all the geometric configurations with ones obtained in the special case of Chaplygin gas. (shrink)

Understanding the impact of robot errors in child-robot-interactions (CRI) is critical, as current technological systems are still limited and may randomly present a variety of mistakes during interactions with children. In this study we manipulate a task-based error of a NAO robot during a semi-autonomous computational thinking task implemented with the Cozmo robot. Data from 72 children aged 7–10 were analysed regarding their attitudes towards NAO (social trust, competency trust, liking, and perceived agency), their behaviour towards the robot (self-disclosure, following (...) recommendations), as well as their task performance. We did not find quantitative effects of the robot’s error on children’s self-reported attitudes, behaviour, or task performance. Age was also not significantly related to either social attitudes or behaviours towards NAO, although there were some age-related differences in task performance. Potential reasons behind the lack of statistical effects and limitations of the study with regards to the manipulation of robot errors are discussed and insights into the design of future CRI studies provided. (shrink)