Non-causal computation

Computation models such as circuits describe sequences of computation steps that are carried out one after the other. In other words, algorithm design is traditionally subject to the restriction imposed by a fixed causal order. We address a novel computing paradigm beyond quantum computing, replacing this assumption by mere logical consistency: We study non-causal circuits, where a fixed time structure within a gate is locally assumed whilst the global causal structure between the gates is dropped. We present examples of logically consistent non- causal circuits outperforming all causal ones; they imply that suppressing loops entirely is more restrictive than just avoiding the contradictions they can give rise to. That fact is already known for correlations as well as for communication, and we here extend it to computation.Comment: 6 pages, 4 figure

Causal loops: logically consistent correlations, time travel, and computation

Causal loops are loops in cause-effect chains: An effect can be the cause of that effect's cause. We show that causal loops can be unproblematic, and explore them from different points of view. This thesis is motivated by quantum theory, general relativity, and quantum gravity. By accepting all of quantum theory one can ask whether the possibility to take superpositions extends to causal structures. Then again, quantum theory comes with conceptual problems: Can we overcome these problems by dropping causality? General relativity is consistent with space-time geometries that allow for time-travel: What happens to systems traveling along closed time-like curves, are there reasons to rule out the existence of closed time-like curves in nature? Finally, a candidate for a theory of quantum gravity is quantum theory with a different, relaxed space-time geometry. Motivated by these questions, we explore the classical world of the non-causal. This world is non-empty; and what can happen in such a world is sometimes weird, but not too crazy. What is weird is that in these worlds, a party (or event) can be in the future and in the past of some other party (time travel). What is not too crazy is that this theoretical possibility does not lead to any contradiction. Moreover, one can identify logical consistency with the existence of a unique fixed point in a cause-effect chain. This can be understood as follows: No fixed point is the same as having a contradiction (too stiff), multiple fixed points, then again, is the same as having an unspecified system (too loose). This leads to a series of results in that field: Characterization of classical non-causal correlations, closed time- like curves that do not restrict the actions of experimenters, and a self-referential model of computation. We study the computational power of this model and use it to upper bound the computational power of closed time-like curves. Time travel has ever since been term weird, what we show here, however, is that time travel is not too crazy: It is not possible to solve hard problems by traveling through time. Finally, we apply our results on causal loops to other fields: an analysis with Kolmogorov complexity, local and classical simulation of PR-box correlations with closed time-like curves, and a short note on self-referentiality in language

Essai: From iron cages to liquid modernity in organization analysis

Historically, the metaphor of the iron cage, as a key component of Weber's sociological imagination, has played a central role in organization studies. It did so both in its initial role in the sociology of bureaucracy and in its reinterpretation in institutional terms. More recently, there have been claims that the metaphors should change. The implications of this for the analysis of organization are the subject of this paper. To address these changes, we draw on debates that have been current in the sociology of consumption, where there is an emergent consensus that there has been a shift to an increasingly liquid modernity. We ask, what are the implications of liquid modernity when viewed not solely in the sphere of consumption but when we shift focus back to the sphere of production - to organizations? © The Author(s), 2010

The relation between spatial perspective taking and inhibitory control in 6-year-old children

Developmental research on spatial perspective taking has shown that young children are able to solve perspective-taking problems under favorable circumstances, but they have difficulties succeeding in classic tasks involving a conflict between one’s own perspective and that of another observer. To date, little is known about the reasons for young children’s difficulties in dealing with incongruent perspectives. Based on the assumption that one’s own perspective has to be ignored to imagine someone else’s perspective, it was investigated whether perspective taking is related to inhibitory control in 6-year-olds (N = 140). An adapted version of the ‘Fruit Stroop task’, appropriate for preschool children, was used to assess inhibitory control. Perspective taking was assessed using the ‘Perspective-Taking Test for Children’. Other spatial and nonspatial abilities were assessed to investigate the specificity of the relation. Results showed a significant correlation between perspective taking and inhibitory control, even when controlled for age, verbal-IQ, and socio-economic status. However, no significant correlations between inhibition and other spatial abilities were found, indicating a specific relation between inhibition and perspective taking. A linear regression analysis showed that, even after accounting for effects of control variables as well as other mental transformation abilities, inhibition accounted for a significant part of the variance in perspective-taking performance. The present findings provide valuable information on what contributes to individual differences in perspective taking, which is an important aspect of everyday cognition and bears relevance for reasoning in technical domains