On the Kinetic Roughening in Polymer Film Growth by Vapor Deposition

This is a Comment on a recent publication: Y.-P. Zhao et al., Phys. Rev. Lett. 85, 3229 (2000). In the Letter, the authors report on an experimental investigation of polymeric (p-xylene) thin film growth and propose a new universality class not previously known. Here, we point out that the critical exponents reported in the Letter are consistent with the critical exponents of Das Sarma-Tamborenea growth model.Comment: 2 pages, 1 figure include

Vertical diversity and equilbrium growth

This paper examines the effect of an increase in vertical diversity in workers' skill on the long run growth rate of an economy. It uses a two-secror model where the techonology of the consumption-good sector is supermodular and that of the R&D sector is submodular. By adopting Grossman and Maggi's(2000) model to a framework of growth based on R&D, it shows first that diversity is condutive to growth. As the main innovation, communication gap is introduced among workers. It is then shown that growth may not be increasing with diversity. There may be an inverse-U shaped relationship.Diversity, talent distribution, supermodular technology, submodular technology, growth, skill, R&D, innovations

Three Brane Action and The Correspondence Between N=4 Yang Mills Theory and Anti De Sitter Space

Recently, a relation between N=4 Super Yang Mills in 3+1 dimensions and supergravity in an $AdS_5$ background has been proposed. In this paper we explore the idea that the correspondence between operators in the Yang Mills theory and modes of the supergravity theory can be obtained by using the D3 brane action. Specifically, we consider two form gauge fields for this purpose. The supergravity analysis predicts that the operator which corresponds to this mode has dimension six. We show that this is indeed the leading operator in the three brane Dirac-Born-Infeld and Wess-Zumino action which couples to this mode. It is important in the analysis that the brane action is expanded around the anti de-Sitter background. Also, the Wess-Zumino term plays a crucial role in cancelling a lower dimension operator which appears in the the Dirac-Born-Infeld action.Comment: 12 pages, LaTex, no figures; error in the form of the final dimension six operator corrected, some references and comments added, main conclusions unchange