Discrete Symmetries of Complete Intersection Calabi-Yau Manifolds

In this paper, we classify non-freely acting discrete symmetries of complete intersection Calabi- Yau manifolds and their quotients by freely-acting symmetries. These non-freely acting symmetries can appear as symmetries of low-energy theories resulting from string compactifications on these Calabi-Yau manifolds, particularly in the context of the heterotic string. Hence, our results are relevant for four-dimensional model building with discrete symmetries and they give an indication which symmetries of this kind can be expected from string theory. For the 1695 known quotients of complete intersection manifolds by freely-acting discrete symmetries, non-freely-acting, generic symmetries arise in 381 cases and are, therefore, a relatively common feature of these manifolds. We find that 9 different discrete groups appear, ranging in group order from 2 to 18, and that both regular symmetries and R-symmetries are possible.Comment: 23 pages; minor changes: updated a reference, removed unclear sentenc

Return on investment of high-quality outplacement programs

Investments ; Unemployment ; Labor productivity

Synchronisation of stochastic oscillators in biochemical systems

A formalism is developed which describes the extent to which stochastic oscillations in biochemical models are synchronised. It is based on the calculation of the complex coherence function within the linear noise approximation. The method is illustrated on a simple example and then applied to study the synchronisation of chemical concentrations in social amoeba. The degree to which variation of rate constants in different cells and the volume of the cells affects synchronisation of the oscillations is explored, and the phase lag calculated. In all cases the analytical results are shown to be in good agreement with those obtained through numerical simulations

Intrinsic noise and two-dimensional maps: Quasicycles, quasiperiodicity, and chaos

We develop a formalism to describe the discrete-time dynamics of systems containing an arbitrary number of interacting species. The individual-based model, which forms our starting point, is described by a Markov chain, which in the limit of large system sizes is shown to be very well-approximated by a Fokker-Planck-like equation, or equivalently by a set of stochastic difference equations. This formalism is applied to the specific case of two species: one predator species and its prey species. Quasi-cycles --- stochastic cycles sustained and amplified by the demographic noise --- previously found in continuous-time predator-prey models are shown to exist, and their behavior predicted from a linear noise analysis is shown to be in very good agreement with simulations. The effects of the noise on other attractors in the corresponding deterministic map, such as periodic cycles, quasiperiodicity and chaos, are also investigated.Comment: 21 pages, 12 figure

Suppressing escape events in maps of the unit interval with demographic noise

We explore the properties of discrete-time stochastic processes with a bounded state space, whose deterministic limit is given by a map of the unit interval. We find that, in the mesoscopic description of the system, the large jumps between successive iterates of the process can result in probability leaking out of the unit interval, despite the fact that the noise is multiplicative and vanishes at the boundaries. By including higher-order terms in the mesoscopic expansion, we are able to capture the non-Gaussian nature of the noise distribution near the boundaries, but this does not preclude the possibility of a trajectory leaving the interval. We propose a number of prescriptions for treating these escape events, and we compare the results with those obtained for the metastable behavior of the microscopic model, where escape events are not possible. We find that, rather than truncating the noise distribution, censoring this distribution to prevent escape events leads to results which are more consistent with the microscopic model. The addition of higher moments to the noise distribution does not increase the accuracy of the final results, and it can be replaced by the simpler Gaussian noise.Comment: 14 pages, 13 figure

A Metamodel for Jason BDI Agents

In this paper, a metamodel, which can be used for modeling Belief-Desire-Intention (BDI) agents working on Jason platform, is introduced. The metamodel provides the modeling of agents with including their belief bases, plans, sets of events, rules and actions respectively. We believe that the work presented herein contributes to the current multi-agent system (MAS) metamodeling efforts by taking into account another BDI agent platform which is not considered in the existing platform-specific MAS modeling approaches. A graphical concrete syntax and a modeling tool based on the proposed metamodel are also developed in this study. MAS models can be checked according to the constraints originated from the Jason metamodel definitions and hence conformance of the instance models is supplied by utilizing the tool. Use of the syntax and the modeling tool are demonstrated with the design of a cleaning robot which is a well-known example of Jason BDI architecture

Intrinsic noise and discrete-time processes

A general formalism is developed to construct a Markov chain model that converges to a one-dimensional map in the infinite population limit. Stochastic fluctuations are therefore internal to the system and not externally specified. For finite populations an approximate Gaussian scheme is devised to describe the stochastic fluctuations in the non-chaotic regime. More generally, the stochastic dynamics can be captured using a stochastic difference equation, derived through an approximation to the Markov chain. The scheme is demonstrated using the logistic map as a case study.Comment: Modified version accepted for publication in Phys. Rev. E Rapid Communications. New figures adde

A Model-Driven Engineering Technique for Developing Composite Content Applications

Composite Content Applications (CCA) are cross-functional process solutions built on top of Enterprise Content Management systems assembled from pre-built components. Considering the complexity of CCAs, their analysis and development need higher level of abstraction. Model-driven engineering techniques covering the use of Domain-specific Modeling Languages (DSMLs), can provide the abstraction in question by moving software development from code to models which may increase productivity and reduce development costs. Hence, in this paper, we present MDD4CCA, a DSML for developing CCAs. The DSML presents an abstract syntax, a concrete syntax, and an operational semantics, including model-to-model and model-to-code transformations for CCA implementations. Use of the proposed language is evaluated within an industrial case study

Talking about Hillsborough: ‘panic’ as discourse in survivors' accounts of the 1989 football stadium disaster

Popular representations of crowd behaviour in disasters are often characterised by irrationalist discourses, in particular ‘mass panic’ despite their rejection by current scientific research. This paper reports an analysis of four survivors' accounts of the 1989 Hillsborough disaster to investigate if and how they used the term ‘panic’. Reference to ‘panic’ occurred frequently, but more detailed analysis found that their accounts did not match the classic criteria for ‘mass panic’ (e.g. uncontrolled emotion and selfish behaviour). Indeed, participants referred to ‘orderly’ behaviour, and cooperation, even when they said the threat of death was present. ‘Panic’ was therefore being used as a description of events that was not consistent. A discourse analysis of usage suggests that participants used ‘panic’ not only to convey feelings of fear and distress but also to apportion culpability towards the actions of the police who they considered responsible for the tragedy (as indeed recent independent research has confirmed). It is concluded that the term ‘panic’ is so deeply embedded in popular discourse that people may use it even when they have reason to reject its irrationalist implications. Alternative discourses that emphasise collective resilience in disasters are suggested