K. Young

High voltage power supply

The present invention relates generally to control of the high-voltage power supply, specifically, while reducing unwanted self-resonance of the self-oscillating flyback transformer windings, relates to controlling the high voltage power from the low voltage power supply. .FIELD 1

Late-time tail of wave propagation on curved spacetime.

The late time behavior of waves propagating on a general curved spacetime is studied. The late time tail is not necessarily an inverse power of time. Our work extends, places in context, and provides understanding for the known results for the Schwarzschild spacetime. Analytic and numerical results are in excellent agreement.

Research assessment in Hong Kong

A system of research assessment was developed and implemented inHong Kong during the period from 1991 to 1994 as an input to theassessment of the public recurrent funding allocations of theterritorys higher education institutions and as an extension ofthe University Grants Committees other quality assuranceactivities. Refinements were subsequently introduced for the nexttwo assessment exercises in 1996 and 1999. This paper describesthe evolution of the process, identifies some significantdifferences from that in the UK on which it was modelled, andevaluates the 1999 research assessment exercise, in particularthe application in that context of the Carnegie Foundationsdefinitions of research and research-related scholarlyactivities, viz. the scholarships of ``discovery, integration,application and teaching.

Foreign exchange market as a lattice gauge theory

A simple model of the foreign exchange market is exactly a lattice gauge theory. Exchange rates are the exponentials of gauge potentials defined on spatial links while interest rates are related to gauge potentials on temporal links. Arbitrage opportunities are given by nonzero values of the gauge-invariant field tensor or curvature defined on closed loops. Arbitrage opportunities involving cross-rates at one time are “magnetic fields,” while arbitrage opportunities involving future contracts are “electric fields.”

QUASINORMAL MODE EXPANSION FOR LINEARIZED WAVES IN GRAVITATIONAL SYSTEMS

The quasinormal modes (QNMs) of gravitational systems modeled by the Klein-Gordon equation with effective potentials are studied in analogy to the QNMs of optical cavities. Conditions are given for the QNMs to form a complete set, i.e., for the Greens function to be expressible as a sum over QNMs, answering a conjecture by Price and Husain [Phys. Rev. Lett. {bf 68}, 1973 (1992)]. In the cases where the QNM sum is divergent, procedures for regularization are given. The crucial condition for completeness is the existence of spatial discontinuities in the system, e.g., the discontinuity at the stellar surface in the model of Price and Husain.

Advance of perihelion

The advance of perihelion, in particular for Mercury, is regarded as a classical test of general relativity, but a number of other (in some cases much larger) contributions to this phenomenon are seldom discussed in detail in textbooks. This paper presents a unified framework for evaluating the advance of perihelion due to (a) general relativity, (b) the solar quadrupole moment, and (c) planetary perturbations, the last in a ring model where the mass of each perturbing planet is “smeared out” into a coplanar circular orbit. The exact solution of the ring model agrees to within 4% with the usually quoted figure. Time-dependent contributions beyond the ring model contain some surprising features: they are not small, and some with long periods could mimic a secular advance.

Field theory renormalization using the Callan-Symanzik equation

Abstract Quantum electrodynamics (QED) is renormalized by exploiting the Callan-Symanzik equations for broken scale invariance. The basic idea is to make enough mass insertions in a Green function G requiring renormalization so that the resulting Green function G ′ (a) is superficially convergent and (b) has a skeleton expansion. G ′ is trivially renormalized and G is recovered through the Callan-Symanzik equations. This offers a simple proof that QED can be multiplicatively renormalized. This technique avoids all divergent integrals, in particular the difficult overlapping divergences. Moreover, it is shown that the renormalized Green functions calculated according to the recipe given by Bogoliubov, Parasiuk and Hepp agree with the result of the present analysis. This offers an alternate and somewhat simpler proof that the BPH method (a) gives a finite answer and (b) corresponds to a multiplicative renormalization. The method used is generalizable to other field theories in an obvious manner.

Criterion-referenced and norm-referenced assessments: compatibility and complementarity

The tension between criterion-referenced and norm-referenced assessment is examined in the context of curriculum planning and assessment in outcomes-based approaches to higher education. This paper argues the importance of a criterion-referenced assessment approach once an outcomes-based approach has been adopted. It further discusses the implementation of criterion-referenced assessment, considering to what extent the criteria and standards adopted are implicitly norm referenced. It introduces a compatible interpretation of criterion-referenced and norm-referenced assessments in higher education, and illustrates how their combined use can avoid grade inflation and also provide useful information to educators, employers and learners. Instead of seeing criterion referencing and norm referencing as a dichotomy, assessment in higher education benefits from their synthesis through a feedback loop that emphasises alignment between learning and assessment; such feedback and alignment are essential features of quality assurance and enhancement.

Momentum of light in a refracting medium

It is pointed out that neither Minkowski’s nor Abraham’s proposal gives correctly the momentum density of light in a refracting medium. The correct result due to Peierls is simply derived. The imbalance of momentum flux at an interface corresponds to a force on the surface, and this is contrasted with a delayed force due to a finite beam width.

QUASINORMAL MODES OF DIRTY BLACK HOLES

Quasinormal mode (QNM) gravitational radiation from black holes is expected to be observed in a few years. A perturbative formula is derived for the shifts in both the real and the imaginary part of the QNM frequencies away from those of an idealized isolated black hole. The formulation provides a tool for understanding how the astrophysical environment surrounding a black hole, e.g., a massive accretion disk, affects the QNM spectrum of gravitational waves. We show, in a simple model, that the perturbed QNM spectrum can have interesting features.