A speculative remark on holography

Holography suggests a considerable reduction of degrees of freedom in theories with gravity. However it seems to be difficult to understand how holography could be realized in a closed re--contracting universe. In this letter we claim that a scenario which achieves that goal will eliminate all spatial degrees of freedom. This would require a different concept of quantum mechanics and would imply an intriguing increase of power for the natural laws.Comment: 14 pages, a reference adde

Wealth inequality in the United States and Great Britain

In this paper we describe the household wealth distribution in the US and UK, and compare both wealth inequality and the form in which wealth is held. Unconditionally, there are large differences in financial wealth between the two countries at the top fifth of the wealth distribution. And even after controlling for age and income differences between the two countries, we show that the median US household accumulates more financial wealth than their UK counterpart. We explore a number of alternative reasons for these differences and reject some explanations as implausible. These include differential receipt of financial inheritances or desired bequests, and differential average rates of return to corporate equity or housing. While less certain, we also argue that the differences that are concentrated among the older well-to-do are not likely due to differences in income or employment risks, savings for college expenses, or changes in permanent income. Some of the observed differences are due to what we refer to as "initial conditions", in particular previously high rates of corporate equity ownership in the US and housing ownership among young British households. But since these differences existed even in the early 1980s, initial conditions only provide a partial explanation. One further possibility may be that due to forced and voluntary annuitization of retirement incomes, older British households face considerably less longevity risk. Looking more widely, however, we find wealth held in different forms across the two countries, in particular in housing, which to some extent offsets the differences we observe in financial wealth patterns. We therefore point out that it is important that comparative studies compare genuine economic phenomena (such as the ability to smooth consumption) rather than particular economic measurements (such as the level of wealth in any one particular form). We also argue that it is crucial that comparative exercises of this form acknowledge the importance of institutional differences across countries, and in this particular comparison the role of housing markets, annuity markets and stock markets appear crucial and all merit further more detailed research. On balance, we are encouraged by the degree to which a detailed investigation can point to potential explanations of observed wealth differences between the two countries, and such an investigation will also lead to a deeper understanding of the household wealth accumulation process more generally.

An Abstraction Theory for Qualitative Models of Biological Systems

Multi-valued network models are an important qualitative modelling approach used widely by the biological community. In this paper we consider developing an abstraction theory for multi-valued network models that allows the state space of a model to be reduced while preserving key properties of the model. This is important as it aids the analysis and comparison of multi-valued networks and in particular, helps address the well-known problem of state space explosion associated with such analysis. We also consider developing techniques for efficiently identifying abstractions and so provide a basis for the automation of this task. We illustrate the theory and techniques developed by investigating the identification of abstractions for two published MVN models of the lysis-lysogeny switch in the bacteriophage lambda.Comment: In Proceedings MeCBIC 2010, arXiv:1011.005