Moduli spaces of torsion sheaves on K3 surfaces and derived equivalences

We show that for many moduli spaces M of torsion sheaves on K3 surfaces S, the functor D(S) -> D(M) induced by the universal sheaf is a P-functor, hence can be used to construct an autoequivalence of D(M), and that this autoequivalence can be factored into geometrically meaningful equivalences associated to abelian fibrations and Mukai flops. Along the way we produce a derived equivalence between two compact hyperkaehler 2g-folds that are not birational, for every g >= 2. We also speculate about an approach to showing that birational moduli spaces of sheaves on K3 surfaces are derived-equivalent.Comment: 28 pages. typos corrected. final version to appear in JLM

Stark ladders as tunable far-infrared emitters

A superlattice of GaAs/Ga(1 – x)Al(x)As quantum wells forms a Stark ladder under the influence of a perpendicular electric field. A two level incoherent emitter system, formed by radiative intersubband transitions between adjacent wells, is investigated as a tunable far-infrared radiation source. Intersubband transition rates are calculated at 4, 77, and 300 K for applied fields from 0 to 40 kV cm(–1). It is shown that the quantum efficiency of the radiative emission reaches a maximum at low temperatures for a field of 32 kV cm(–1). Under these conditions the emission wavelength is 38 µm with an estimated power output of 1.1 mW. © 1998 American Institute of Physics

Free Energy and Phase Transition of the Matrix Model on a Plane-Wave

It has recently been observed that the weakly coupled plane wave matrix model has a density of states which grows exponentially at high energy. This implies that the model has a phase transition. The transition appears to be of first order. However, its exact nature is sensitive to interactions. In this paper, we analyze the effect of interactions by computing the relevant parts of the effective potential for the Polyakov loop operator in the finite temperature plane-wave matrix model to three loop order. We show that the phase transition is indeed of first order. We also compute the correction to the Hagedorn temperature to order two loops.Comment: 24 page

Yield Management in the Airline Industry

This is it! This is a shot across our bow! If we don\u27t invent a way to deal with (yield management), we\u27re history! - Donald Burr, Former CEO of People\u27s Express. Immersed in the age of the internet, most prospective travelers have searched for, and have purchased airline tickets online. In doing so, a varying range of prices and restrictions were inevitably discovered. One week, a roundtrip ticket on a given flight may be quoted at $280, a week later at$360, and a week prior to the flight, $840! The constant fluctuation in price is due to the practice of yield management, sometimes referred to as revenue management. The airline industry was the first to develop and implement this system, and its use has resulted in substantial revenue gains for the industry as a whole