Supersymmetric Electroweak Baryogenesis in the WKB approximation

We calculate the baryon asymmetry generated at the electroweak phase transition in the minimal supersymmetric standard model, treating the particles in a WKB approximation in the bubble wall background. A set of diffusion equations for the particle species relevant to baryon generation, including source terms arising from the CP violation associated with the complex phase $\delta$ of the $\mu$ parameter, are derived from Boltzmann equations, and solved. The conclusion is that $\delta$ must be \gsim 0.1 to generate a baryon asymmetry consistent with nucleosynthesis. We compare our results to several other recent computations of the effect, arguing that some are overestimates.Comment: 12 pages, 1 figure, corrected some criticisms of hep-ph/9702409; to appear in Phys. Lett.

Active coupled-resonator optical waveguides. I. Gain enhancement and noise

We use a tight-binding formalism in the time domain to analyze the effect of resonant gain enhancement and spontaneous emission noise in amplifying coupled-resonator optical waveguides (CROWs). We find the net amplification of a wave propagating in a CROW does not always vary with the group velocity, and depends strongly on the termination and excitation of these structures. The signal-to-noise ratio and noise figure of CROW amplifiers are derived in the tight-binding formalism as well. The physical interpretations and practical consequences of the theoretical results are discussed

Innovation in services: corporate culture and investment banking

The article discusses service innovation in the investment banking industry. Service industry innovations differ from innovations in industries that produce physical products because they rarely have intellectual property and patent protections. However, investment banking services are typically a series of interrelated businesses such as consulting, wealth management and accounting, and innovations require a business wide coordinated approach. The authors argue that a strong corporate culture can support rather than hinder innovation. The creation of such a culture requires strong leadership and an emphasis on innovation in hiring and promotions

The QCD sign problem as a total derivative

We consider the distribution of the complex phase of the fermion determinant in QCD at nonzero chemical potential and examine the physical conditions under which the distribution takes a Gaussian form. We then calculate the baryon number as a function of the complex phase of the fermion determinant and show 1) that the exponential cancellations produced by the sign problem take the form of total derivatives 2) that the full baryon number is orthogonal to this noise. These insights allow us to define a self-consistency requirement for measurements of the baryon number in lattice simulations.Comment: 5 pages, reference added, version to appear in PRD rapid communication

The density in the density of states method

It has been suggested that for QCD at finite baryon density the distribution of the phase angle, i.e. the angle defined as the imaginary part of the logarithm of the fermion determinant, has a simple Gaussian form. This distribution provides the density in the density of states approach to the sign problem. We calculate this phase angle distribution using i) the hadron resonance gas model; and ii) a combined strong coupling and hopping parameter expansion in lattice gauge theory. While the former model leads only to a Gaussian distribution, in the latter expansion we discover terms which cause the phase angle distribution to deviate, by relative amounts proportional to powers of the inverse lattice volume, from a simple Gaussian form. We show that despite the tiny inverse-volume deviation of the phase angle distribution from a simple Gaussian form, such non-Gaussian terms can have a substantial impact on observables computed in the density of states/reweighting approach to the sign problem.Comment: 43 pages, 4 figure

Optical bright and dark states in side-coupled resonator structures

We analyze side-coupled standing-wave cavity structures consisting of Fabry-Perot and photonic crystal resonators coupled to two waveguides. We show that optical bright and dark states, analogous to those observed in coherent light-matter interactions, can exist in these systems. These structures may be useful for variable, switchable delay lines

Core content modules at Leeds Metropolitan University

As part of Leeds Metropolitan University’s review of the postgraduate curriculum in 2012–13, Libraries and Learning Innovation (LLI) was asked to lead a project group to create two core content modules for use at Level 7 (Masters level) in Research Practice and Project Management. The rationale for choosing these two areas was the sheer number of modules in these subjects taught across a wide range of disciplines, each of which is currently designed and populated by individual course teams. The group consisted of representatives from the University’s Centre for Teaching and Learning, academic staff, learning technologists and academic librarians, and was chaired by the Associate Director of LLI, Wendy Luker