Money stock control and its implications for monetary policy

Monetary policy ; Money supply

Exploring non-adiabatic approximations to the exchange-correlation functional of TDDFT

A decomposition of the exact exchange-correlation potential of time-dependent density functional theory into an interaction component and a kinetic component offers a new starting point for non-adiabatic approximations. The components are expressed in terms of the exchange-correlation hole and the difference between the one-body density matrix of the interacting and Kohn-Sham systems, which must be approximated in terms of quantities accessible from the Kohn-Sham evolution. We explore several preliminary approximations, evaluate their fulfillment of known exact conditions, and test their performance on simple model systems for which available exact solutions indicate the significance of going beyond the adiabatic approximation.Fil: Fuks, Johanna Ildemar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Lacombe, Lionel. University of New York; Estados UnidosFil: Nielsen, Søren E. B.. Max Planck Institute for the Structure and Dynamics of Matter; Alemania. Center for Free-Electron Laser Science; AlemaniaFil: Maitra, Neepa T.. University of New York; Estados Unido

On the Maximum Mass of Accreting Primordial Supermassive Stars

Supermassive primordial stars are suspected to be the progenitors of the most massive quasars at z~6. Previous studies of such stars were either unable to resolve hydrodynamical timescales or considered stars in isolation, not in the extreme accretion flows in which they actually form. Therefore, they could not self-consistently predict their final masses at collapse, or those of the resulting supermassive black hole seeds, but rather invoked comparison to simple polytropic models. Here, we systematically examine the birth, evolution and collapse of accreting non-rotating supermassive stars under accretion rates of 0.01-10 solar masses per year, using the stellar evolution code KEPLER. Our approach includes post-Newtonian corrections to the stellar structure and an adaptive nuclear network, and can transition to following the hydrodynamic evolution of supermassive stars after they encounter the general relativistic instability. We find that this instability triggers the collapse of the star at masses of 150,000-330,000 solar masses for accretion rates of 0.1-10 solar masses per year, and that the final mass of the star scales roughly logarithmically with the rate. The structure of the star, and thus its stability against collapse, is sensitive to the treatment of convection, and the heat content of the outer accreted envelope. Comparison with other codes suggests differences here may lead to small deviations in the evolutionary state of the star as a function of time, that worsen with accretion rate. Since the general relativistic instability leads to the immediate death of these stars, our models place an upper limit on the masses of the first quasars at birth.Comment: 5 pages, 4 figures. Accepted ApJ letter

Information flow in a kinetic ising model peaks in the disordered phase

There is growing evidence that for a range of dynamical systems featuring complex interactions between large ensembles of interacting elements, mutual information peaks at order-disorder phase transitions. We conjecture that, by contrast, information flow in such systems will generally peak strictly on the disordered side of a phase transition. This conjecture is verified for a ferromagnetic 2D lattice Ising model with Glauber dynamics and a transfer entropy-based measure of systemwide information flow. Implications of the conjecture are considered, in particular, that for a complex dynamical system in the process of transitioning from disordered to ordered dynamics (a mechanism implicated, for example, in financial market crashes and the onset of some types of epileptic seizures); information dynamics may be able to predict an imminent transition

Evolving individualised consumer products

The origins of this project began in 2002 with experimentation into the application of computer generated random form to 3D product design. Advances in the Rapid Prototyping industry were offering the possibility of mass-produced one-off consumer products. Computer based 3D solid models were created that would randomly mutate within parameter envelopes set by the designer. At any given point the mutation could be halted and a real-world product generated via digital manufacture (Rapid Prototyping). This fi rst stage of the work has already been reported on (Atkinson and Dean, 2003). The next phase of the program has been to introduce evolutionary development so that, via the computer generated random mutation, the model develops generation by generation in a desired direction (though not necessarily to a predictable outcome). This requires an element of selection. There are several examples of computer based evolutionary design experiments that use human by-eye selection methods, notably Richard Dawkins’ ‘Biomorph’ system (Dawkins 1993). The aim of this project is an automated system that selects on some measure of desirability and rejects outright any functional failures. Each FutureFactories product form is defined by a parametric CAD (Computer-Aided-Design) model. When evolution is initiated, a series of mutant designs are generated each with a single parameter, selected at random, adjusted by a small pre-determined step. The step may be positive or negative; this again is determined at random. The resulting set of mutant progeny is then assessed for their visual ‘success’ using a quotient. The quotient aims to access the level of visual interest in a form. As the application is 3D products, there are physical parameters to consider, for instance ‘hard points’ generated by the envelopes of internal components which may not be intruded upon. If any of the offspring do not meet the necessary physical criteria they are rejected. Animation is employed to extrapolate between iteration to present the evolution as a smooth metamorphosis. Product forms and associated development criteria have been created capable of evolutionary development over many generations. The resulting designs are both surprising and unpredictable

‘Future Factories’: developing individualised production methods

'Future Factories' is an exploration of the possibilities for flexibility in the manufacture of artefacts inherent in digitally driven production techniques. The concept considers individualised production – in which a random element of variance over parameters such as the relative positioning of features, scale, proportion, surface texture, and the like is introduced by the computer within a parameter envelope defined by the designer. This paper is the feasibility study of, and design of, a production system for the 'Future Factories' concept. In 'Future Factories', a production system is envisaged in which the consumer is presented with a 3D digital model of the design. The design is presented as an animation showing the design morphing within a parameter envelope specified by the designer. At any given point the consumer may freeze the design, place an order, and generate the relevant digital production files (.stl etc.). A unique, individual artefact will then be manufactured using Rapid Prototyping techniques. This may be achieved directly, via Stereo Laser Sintering in a suitable material for example, or indirectly via the production of a single use tool or pattern. This paper presents results from research conducted as part of the Designer in Residence project at the School of Design Technology, University of Huddersfield. Firstly a selection of design concepts with associated parameter envelopes are created using relevant 3D design software. Animations are then created showing the design moving within its parameter envelope. A new computer program is being developed to enable the generation of digital production files direct from a selected animation frame. There will be a study of existing rapid prototyping techniques with regard to their suitability for direct manufacture of this type and speculation on future potential