Symmetrization procedures for the isoperimetric problem in symmetric spaces of noncompact type

We establish a new symmetrization procedure for the isoperimetric problem in symmetric spaces of noncompact type. This symmetrization generalizes the well known Steiner symmetrization in euclidean space. In contrast to the classical construction the symmetrized domain is obtained by solving a nonlinear elliptic equation of mean curvature type. We conclude the paper discussing possible applications to the isoperimetric problem in symmetric spaces of noncompact type.Comment: 28 pages, 1 figur

Game Harmony: A Short Note

Strategic uncertainty in game theory may have two different general sources, either alone or in combination: uncertainty because of the existence of a coordination problem, and uncertainty because of a conflict between one own and the other n players' interests. Game harmony is conceived as a generic game property that describes how harmonious (non-conflictual) or disharmonious (conflictual) the interests of the n players are, as embodied in the game payoffs. Pure coordination games are examples of games with maximal game harmony; zero sum games are examples of games with very low game harmony. This note briefly describes attempts to measure game harmony simply as a real-valued number

Populations in statistical genetic modelling and inference

What is a population? This review considers how a population may be defined in terms of understanding the structure of the underlying genetics of the individuals involved. The main approach is to consider statistically identifiable groups of randomly mating individuals, which is well defined in theory for any type of (sexual) organism. We discuss generative models using drift, admixture and spatial structure, and the ancestral recombination graph. These are contrasted with statistical models for inference, principle component analysis and other `non-parametric' methods. The relationships between these approaches are explored with both simulated and real-data examples. The state-of-the-art practical software tools are discussed and contrasted. We conclude that populations are a useful theoretical construct that can be well defined in theory and often approximately exist in practice

Effects of Team-Based Computer Interaction: The Media Equation and Game Design Considerations

The current paper applies media equation research to video game de-sign. The paper presents a review of the existing media equation research, de-scribes a specific study conducted by the authors, discusses how the findings of the study can be used to inform future game design, and explores how other media equation findings might be incorporated into game design. The specific study, discussed in detail in the paper, explores the notion of team formation between humans and computer team-mates. The results show that while highly experienced users will accept a computer as a team-mate, they tend to react more negatively towards the computer than to human teammates (a ‘Black Sheep’ Effect

Spontaneous emission from a two--level atom tunneling in a double--well potential

We study a two-level atom in a double--well potential coupled to a continuum of electromagnetic modes (black body radiation in three dimensions at zero absolute temperature). Internal and external degrees of the atom couple due to recoil during emission of a photon. We provide a full analysis of the problem in the long wavelengths limit up to the border of the Lamb-Dicke regime, including a study of the internal dynamics of the atom (spontaneous emission), the tunneling motion, and the electric field of the emitted photon. The tunneling process itself may or may not decohere depending on the wavelength corresponding to the internal transition compared to the distance between the two wells of the external potential, as well as on the spontaneous emission rate compared to the tunneling frequency. Interference fringes appear in the emitted light from a tunneling atom, or an atom in a stationary coherent superposition of its center--of--mass motion, if the wavelength is comparable to the well separation, but only if the external state of the atom is post-selected.Comment: 24 pages, 4 figures; improved discussion on the limitations of the theor

Enterprise portals: addressing the organisational and individual perspectives of information systems

Enterprise portals are being viewed as the next generation application platform of choice, offering benefits over both client/server and thin client arrangements. By providing a mediating layer between the information applications and resources of the organisation and the individuals using them, enterprise portals appear to provide a unique context to allow both the organisational and individual perspectives of information systems to be addressed. This study seeks to examine these often competing perspectives of information systems by using an exploratory empirical survey to investigate the actual deployment of enterprise portals within a range of different organisations. It is found that both the individual and organisational benefits that enterprise portals can offer appear to have been recognised, and coherent sets of services addressing each of these perspectives are being developed. Consistent with diffusion and acceptance of technology models, organisations appear to be commencing their portal developments with services that will ensure utilisation by individuals, and are subsequently seeking to realise organisational level benefits