Fermionic Coset Realization of Primaries in Critical Statistical Models

We obtain a fermionic coset realization of the primaries of minimal unitary models and show how their four-point functions may be calculated by the use of a reduction formula. We illustrate the construction for the Ising model, where we obtain an explicit realization of the energy operator, Onsager fermions, as well as of the order and disorder operators realizing the dual algebra, in terms of constrained Dirac fermions. The four-point correlators of these operators are shown to agree with those obtained by other methods.Comment: 26 pages, Latex fil

The wind-sock theory of comet tails

A method is reported for calculating the shapes of ionic comet tails that use the magnetic field along the tail to channel the tail plasma. The local momentum field in the solar wind determines magnetic field line locations along the tail. Thus, the magnetic field acts as a transparent wind sock in trapping field lines in the cometary plasma around the nucleus long enough to be effectively fastened to the comet's head

Lattice sum rules for the colour fields

We analyse the sum rules describing the action and energy in the colour fields around glueballs, torelons and static potentials.Comment: 9 pages LATEX, (typos corrected, to appear in Phys Rev D

Direct measurement of the singlet generation yield in polymer light-emitting diodes

In this study, the singlet and triplet exciton generation yields of a representative blue-emitting conjugated polymer are directly compared using simultaneous optical and electrical excitation measurements. After carefully accounting for bimolecular triplet annihilation and knowing the independently measured solid state inter-system-crossing yield of the polymer, a singlet generation yield of 44% is obtained, in the working device, which is clearly in excess of the simple quantum statistical 25% limit

Axial pumps for propulsion systems

The development of axial flow hydrogen pumps is examined. The design features and the performance data obtained during the course of the development programs are discussed. The problems created by the pump characteristics are analyzed. Graphs of four stage pump performance for various turbine blade configurations are developed. The characteristics and performance of a variety of pumps are included

Competition between platform ecosystems: a longitudinal study of MOOC platforms

The last decade has seen a rise in software-based platforms that engender entirely new ecosystems. In newly emerging platform markets, platforms compete for partners and customers in a rapidly changing environment. Yet, extant research mostly studies platforms\u27 supply-side and demand-side strategies in relatively established platform markets. By combining a market-level and platform-level perspective, our research aims to develop a holistic understanding about the interdependencies between business model decisions, market evolution, and performance outcomes of platforms in emerging markets. We focus on the novel context of Massive Open Online Course (MOOC) platforms, analyzing longitudinal data for 35 MOOC platforms and their ecosystems. To account for the multi-level perspective, our research applies an innovative mixed-methods approach that combines qualitative methods with quan-titative measures and visualizations derived from network analysis. Our findings suggest that platforms in new markets converge towards common business models as market leaders imitate the business model innovations of its smaller competitors to manifest their market position. Based on these analyses, we derive four propositions on how the dynamics of a platform’s business model and ecosystem posi-tion affect each other and the platform’s market performance