Decomposability and modularity of economic interactions

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Appropriability, Patents, and Rates of Innovation in Complex Products Industries

The economic theory of intellectual property rights is based on a rather narrow view of both competition and technological knowledge. We suggest some ways of enriching this framework with a more empirically grounded view of both and, by means of a simulation model, we analyze the impact of different property right regimes on the dynamics of a complex product industry, that is an industry where products are complex multi-component objects and competition takes place mainly through differentiation and component innovation. We show that, as the complexity of the product spaces increases, stronger patent regimes yield lower rates of innovation, lower product quality and lower consumers' welfare. localized ones.patents; appropriability of innovation; complex product industries; industrial dynamics

Wolf-Rayet nebulae as tracers of stellar ionizing fluxes: I. M1-67

We use WR124 (WN8h) and its associated nebula M1-67, to test theoretical non-LTE models for Wolf-Rayet (WR) stars. Lyman continuum ionizing flux distributions derived from a stellar analysis of WR124, are compared with nebular properties via photo-ionization modelling. Our study demonstrates the significant role that line blanketing plays in affecting the Lyman ionizing energy distribution of WR stars, of particular relevance to the study of HII regions containing young stellar populations. We confirm previous results that non-line blanketed WR energy distributions fail to explain the observed nebular properties of M1-67, such that the predicted ionizing spectrum is too hard. A line blanketed analysis of WR124 is carried out using the method of Hillier & Miller (1998), with stellar properties in accord with previous results, except that the inclusion of clumping in the stellar wind reduces its wind performance factor to only approx2. The ionizing spectrum of the line blanketed model is much softer than for a comparable temperature unblanketed case, such that negligible flux is emitted with energy above the HeI 504 edge. Photo-ionization modelling, incorporating the observed radial density distribution for M1-67 reveals excellent agreement with the observed nebular electron temperature, ionization balance and line strengths. An alternative stellar model of WR124 is calculated, following the technique of de Koter et al. (1997), augmented to include line blanketing following Schmutz et al. (1991). Good consistency is reached regarding the stellar properties of WR124, but agreement with the nebular properties of M1-67 is somewhat poorer than for the Hillier & Miller code.Comment: 12 pages, 5 figures, latex2e style file, Astronomy & Astrophysics (accepted

Appropriability, patents, and rates of innovation in complex products industries

The economic theory of intellectual property rights is based on a rather narrow view of both competition and technological knowledge. We suggest some ways of enriching this framework with a more empirically grounded view of both and, by means of a simulation model, we analyze the impact of different property right regimes on the dynamics of a complex product industry, that is an industry where products are complex multi-component objects and competition takes place mainly through differentiation and component innovation. We show that, as the complexity of the product spaces increases, stronger patent regimes yield lower rates of innovation, lower product quality and lower consumers' welfare

Galaxy Groups in the SDSS DR4: I. The Catalogue and Basic Properties

We use a modified version of the halo-based group finder developed by Yang et al. to select galaxy groups from the Sloan Digital Sky Survey (SDSS DR4). In the first step, a combination of two methods is used to identify the centers of potential groups and to estimate their characteristic luminosity. Using an iterative approach, the adaptive group finder then uses the average mass-to-light ratios of groups, obtained from the previous iteration, to assign a tentative mass to each group. This mass is then used to estimate the size and velocity dispersion of the underlying halo that hosts the group, which in turn is used to determine group membership in redshift space. Finally, each individual group is assigned two different halo masses: one based on its characteristic luminosity, and the other based on its characteristic stellar mass. Applying the group finder to the SDSS DR4, we obtain 301237 groups in a broad dynamic range, including systems of isolated galaxies. We use detailed mock galaxy catalogues constructed for the SDSS DR4 to test the performance of our group finder in terms of completeness of true members, contamination by interlopers, and accuracy of the assigned masses. This paper is the first in a series and focuses on the selection procedure, tests of the reliability of the group finder, and the basic properties of the group catalogue (e.g. the mass-to-light ratios, the halo mass to stellar mass ratios, etc.). The group catalogues including the membership of the groups are available at http://gax.shao.ac.cn/data/Group.html and http://www.astro.umass.edu/~xhyang/Group.htmlComment: 19 pages, 12 figures, Accepted for publication in ApJ. Group catalogues are available at http://gax.shao.ac.cn/data/Group.html and http://www.astro.umass.edu/~xhyang/Group.htm

Dusty Wind-Blown Bubbles

Spurred by recent observations of 24 micron emission within wind-blown bubbles, we study the role that dust can play in such environments, and build an approximate model of a particular wind-blown bubble, `N49.' First, we model the observations with a dusty wind-blown bubble, and then ask whether dust could survive within N49 to its present age (estimated to be 5x10^5 to 10^6 years). We find that dust sputtering and especially dust-gas friction would imply relatively short timescales (t ~ 10^4 years) for dust survival in the wind-shocked region of the bubble. To explain the 24 micron emission, we postulate that the grains are replenished within the wind-blown bubble by destruction of embedded, dense cloudlets of ISM gas that have been over-run by the expanding wind-blown bubble. We calculate the ablation timescales for cloudlets within N49 and find approximate parameters for the embedded cloudlets that can replenish the dust; the parameters for the cloudlets are roughly similar to those observed in other nebula. Such dust will have an important effect on the bubble: including simple dust cooling in a wind-blown bubble model for N49, we find that the luminosity is higher by approximately a factor of six at a bubble age of about 10^4 years. At ages of 10^7 years, the energy contained in the bubble is lower by about a factor of eight if dust is included; if dust must be replenished within the bubble, the associated accompanying gas mass will also be very important to wind-blown bubble cooling and evolution. While more detailed models are certainly called for, this work illustrates the possible strong importance of dust in wind-blown bubbles, and is a first step toward models of dusty, wind-blown bubbles.Comment: 13 pages, 14 figures, Accepted to Ap

On the structure of Borel stable abelian subalgebras in infinitesimal symmetric spaces

Let g=g_0+g_1 be a Z_2-graded Lie algebra. We study the posets of abelian subalgebras of g_1 which are stable w.r.t. a Borel subalgebra of g_0. In particular, we find out a natural parametrization of maximal elements and dimension formulas for them. We recover as special cases several results of Kostant, Panyushev, Suter.Comment: Latex file, 35 pages, minor corrections, some examples added. To appear in Selecta Mathematic