Thermodynamics and Self-Gravitating Systems

This work assembles some basic theoretical elements on thermal equilibrium, stability conditions, and fluctuation theory in self-gravitating systems illustrated with a few examples. Thermodynamics deals with states that have settled down after sufficient time has gone by. Time dependent phenomena are beyond the scope of this paper. While thermodynamics is firmly rooted in statistical physics, equilibrium configurations, stability criteria and the destabilizing effect of fluctuations are all expressed in terms of thermodynamic functions. The work is not a review paper but a pedagogical introduction which may interest theoreticians in astronomy and astrophysicists. It contains sufficient mathematical details for the reader to redo all calculations. References are only to seminal works or readable reviews. (Except in the ultimate sub-section.) Delicate mathematical problems are mentioned but are not discussed in detail.Comment: 35 pages,6 figure

Competition or Predation? Schumpeterian Rivalry in Network Markets

We explore the logic of predation and rules designed to prevent it in markets subject to network effects. Although, as many have informally argued, predatory behavior is plausibly more likely to succeed in such markets, we find that it is particularly hard to intervene in network markets in ways that improve welfare. We find that imposition of the leading proposals for rules against predatory pricing may lower or raise consumer welfare, depending on conditions that may be difficult to identify in practice.

Innovation, Rent Extraction, and Integration in Systems Markets

We consider innovation incentives in markets where final goods comprise two strictly complementary components, one of which is monopolized. We focus on the case in which the complementary component is competitively supplied, and in which innovation is important. We explore ways in which the monopoly may have incentives to confiscate efficiency rents in the competitive sector, thus weakening or destroying incentives for independent innovation. We discuss how these problems are affected if the monopolist integrates into the competitive sector.

Innovation, Rent Extraction, and Integration in Systems Markets

We consider innovation incentives in markets where final goods comprise two strictly complementary components, one of which is monopolized. We focus on the case in which the complementary component is competitively supplied, and in which innovation is important. We explore ways in which the monopoly may have incentives to confiscate efficiency rents in the competitive sector, thus weakening or destroying incentives for independent innovation. We discuss how these problems are affected if the monopolist integrates into the competitive sector.

Method for generation of tunable far infrared radiation from two-dimensional plasmons

Tunable far infrared radiation is produced from two-dimensional plasmons in a heterostructure, which provides large inversion-layer electron densities at the heterointerface, without the need for a metallic grating to couple out the radiation. Instead, a light interference pattern is produced on the planar surface of the heterostructure using two coherent laser beams of a wavelength selected to be strongly absorbed by the heterostructure in order to penetrate through the inversion layer. The wavelength of the far infrared radiation coupled out can then be readily tuned by varying the angle between the coherent beams, or varying the wavelength of the two interfering coherent beams, thus varying the periodicity of the photoconductivity grating to vary the wavelength of the far infrared radiation being coupled out