The spinor string in a Clifford substructure of space-time

We resolve the space-time coordinates of Minkowski space into Weyl spinors with components in a split Clifford algebra. Poisson brackets are defined for Clifford-valued canonical variables and applied to the quantization of the point particle and string. In particular, we obtain the Poincar\'e algebra for the quantum string. The Clifford algebra is augmented with the octonions through an R-algebra tensor product and we apply the results of Manogue, Schray and Dray on octonionic Lorentz transformations to obtain a Lorentz invariant string action in ten dimensions.Comment: 17 pages LaTeX. Overlap with arXiv:1406.2830. An appendix has been added with a proof of the Lorentz invariance of an octonionic spinor contractio

Human Biodemography: Some challenges and possibilities

This opinion report - in a series on the future of biodemography - focuses on promising areas that I think will be valuable to develop in the future in order to get a better understanding of the determinants of the health and well-being of elderly people. I discuss two major themes: i) the benefits of strengthening the ties between biodemography and medical-clinical disciplines to better understand the link between functioning/diseases/ vulnerability and mortality, ii) the male-female health-survival paradox (i.e., males report better health than females, but encounter higher mortality at all ages), and how this paradox may shed light on fundamental aging processes.ageing processes, determinants, elderly, longitudinal, male/female differences, mortality

A Cross-Country Study of Market-Based Housing Finance

The possibilities to improve households' eligibility for long-term housing loans at fixed interest rates has been a current topic of public discussion. Yet, credit institutions have difficulties in granting such loans, unless they themselves can acquire fixed-rate funding. In many cases, the only feasible way for them to raise such funding is to issue bonds. In a number of countries, such arrangements are already in use. In this paper we present a cross-country study of housing finance by mortgage-backed bonds. The paper describes and analyses mortgage credit markets in Denmark, Sweden and the United States of America with respect to the institutional structure, loans and bonds characteristics, legal framework and the security underlying the system. We have found that all three markets differ and that these differences originate from the respective countries' national characteristics and financial histories. In Sweden and the United States in particular, the public sector has been involved in developing the system. Generally, long-term credit is offered in all three countries through relatively well-functioning, efficient markets. However, certain problems are common to all. First, the number of outstanding bond series is relatively large. Second, in many housing loans, the borrower has the option to repay the debt prematurely. In these cases, the credit institution may have to avoid maturity matching problems by issuing bonds with unknown maturity. We briefly review the history and present circumstances of Finnish bond issuing credit institutions to elucidate why such institutions play a marginal role. Long ago, bond-issuing mortgage institutions were an essential part of the Finnish financial market, but legislative obstacles to their operations almost killed the industry after World War II. The tax system favoured ordinary banks, and bond emissions were restricted by government regulations. Now, these legal obstacles have been abolished. In the light of both foreign and past domestic experience, such institutions have a market niche. Finally, we discuss some of the problems related to setting up a bond-financed mortgage credit market in Finland.housing loans; bonds; mortgage banks

Sisyphus Effect in Pulse Coupled Excitatory Neural Networks with Spike-Timing Dependent Plasticity

The collective dynamics of excitatory pulse coupled neural networks with spike timing dependent plasticity (STDP) is studied. Depending on the model parameters stationary states characterized by High or Low Synchronization can be observed. In particular, at the transition between these two regimes, persistent irregular low frequency oscillations between strongly and weakly synchronized states are observable, which can be identified as infraslow oscillations with frequencies 0.02 - 0.03 Hz. Their emergence can be explained in terms of the Sisyphus Effect, a mechanism caused by a continuous feedback between the evolution of the coherent population activity and of the average synaptic weight. Due to this effect, the synaptic weights have oscillating equilibrium values, which prevents the neuronal population from relaxing into a stationary macroscopic state.Comment: 18 pages, 24 figures, submitted to Physical Review