A Holographic Path to the Turbulent Side of Gravity

We study the dynamics of a 2+1 dimensional relativistic viscous conformal fluid in Minkowski spacetime. Such fluid solutions arise as duals, under the "gravity/fluid correspondence", to 3+1 dimensional asymptotically anti-de Sitter (AAdS) black brane solutions to the Einstein equation. We examine stability properties of shear flows, which correspond to hydrodynamic quasinormal modes of the black brane. We find that, for sufficiently high Reynolds number, the solution undergoes an inverse turbulent cascade to long wavelength modes. We then map this fluid solution, via the gravity/fluid duality, into a bulk metric. This suggests a new and interesting feature of the behavior of perturbed AAdS black holes and black branes, which is not readily captured by a standard quasinormal mode analysis. Namely, for sufficiently large perturbed black objects (with long-lived quasinormal modes), nonlinear effects transfer energy from short to long wavelength modes via a turbulent cascade within the metric perturbation. As long wavelength modes have slower decay, this lengthens the overall lifetime of the perturbation. We also discuss various implications of this behavior, including expectations for higher dimensions, and the possibility of predicting turbulence in more general gravitational scenarios.Comment: 24 pages, 10 figures; v2: references added, and several minor change

How Design Plays Strategic Roles in Internet Service Innovation: Lessons from Korean Companies

In order to survive in the highly competitive internet business, companies have to provide differentiated services that can satisfy the rapidly changing users’ tastes and needs. Designers have been increasingly committed to achieving user satisfaction by generating and visualizing innovative solutions in new internet service development. The roles of internet service design have expanded from a narrow focus on aesthetics into a more strategic aspect. This paper investigates the methods of managing design in order to enhance companies’ competitiveness in internet business. The main research processes are to: (1) explore the current state of internet service design in Korea through in-depth interviews with professional designers and survey questionnaires to 30 digital design agencies and 60 clients; (2) compare how design is managed between in-house design groups and digital design agencies though the case studies of five Korean companies; and (3) develop a taxonomy characterizing four roles of designers in conjunction with the levels of their strategic contributions to internet service innovation: visualist, solution provider, concept generator, and service initiator. In addition, we demonstrate the growing contributions of the strategic use of design for innovating internet services, building robust brand equity, and increasing business performance. Keywords: Design Management; Internet Business; Internet Service Design; Digital Design; Digital Design Agency; In-House Design Group, Case Study</p

On the Integrability, B\"Acklund Transformation and Symmetry Aspects of a Generalized Fisher Type Nonlinear Reaction-Diffusion Equation

The dynamics of nonlinear reaction-diffusion systems is dominated by the onset of patterns and Fisher equation is considered to be a prototype of such diffusive equations. Here we investigate the integrability properties of a generalized Fisher equation in both (1+1) and (2+1) dimensions. A Painlev\'e singularity structure analysis singles out a special case ($m=2$) as integrable. More interestingly, a B\"acklund transformation is shown to give rise to a linearizing transformation for the integrable case. A Lie symmetry analysis again separates out the same $m=2$ case as the integrable one and hence we report several physically interesting solutions via similarity reductions. Thus we give a group theoretical interpretation for the system under study. Explicit and numerical solutions for specific cases of nonintegrable systems are also given. In particular, the system is found to exhibit different types of travelling wave solutions and patterns, static structures and localized structures. Besides the Lie symmetry analysis, nonclassical and generalized conditional symmetry analysis are also carried out.Comment: 30 pages, 10 figures, to appear in Int. J. Bifur. Chaos (2004

California: Round 1 - State-Level Field Network Study of the Implementation of the Affordable Care Act

This report is part of a series of 21 state and regional studies examining the rollout of the ACA. The national network -- with 36 states and 61 researchers -- is led by the Rockefeller Institute of Government, the public policy research arm of the State University of New York, the Brookings Institution, and the Fels Institute of Government at the University of Pennsylvania.In September 2010, six months after the passage of the Affordable Care Act, California became the first state in the nation to create its own insurance exchange, eventually named Covered California. This accelerated timeline was consistent with California's desire to be, in the words of the state's Health and Human Services Secretary and Exchange Board Chair Diana Dooley, the "lead car" in implementation of federal health care reform. Because of the speed with which it approached this task, as well as the sheer size of its coverage expansion, the decisions California has made have been influential both regionally and nationally. What has transpired in the state has had implications for other states as they addressed difficult issues, including minimizing adverse selection, promoting cost-conscious consumer choice, and seamlessly coordinating with public programs

Growth, debt, and sovereign risk in a small, open economy

The continuing debt crisis that many developing countries have faced in the current decade has underscored the need to understand the relationships between debt accumulation and growth, as well as the need to develop policy approaches that foster adjustment in the external account while maintaining the growth of output. The purpose of this paper is to develop a macroeconomic model for a small open developing economy that borrows abroad. This model will assist in studying the dynamic interaction between debt and growth, as well as the impact of various policies and exogenous shocks on the rate of capital accumulation, the current account and debt. From this analysis, the authors make the following conclusions. An upward shift in the supply of debt leads to a long run decline in external debt, a higher domestic interest rate, less capital stock, and a reduced trade surplus. An increase in the marginal cost of debt may or may not lower long run external debt as well. An increase in productivity raises the long run stock of capital but leaves the level of external debt and the interest rate unchanged in the long run. Finally, fiscal expansion has almost no effect in either the short run or the long run.Economic Theory&Research,Environmental Economics&Policies,Strategic Debt Management,Banks&Banking Reform,Financial Intermediation

Competing to Invest in the Foreign Market

This paper analyzes foreign-direct-investment (FDI) competition in a three-country framework: two Northern countries and one Southern country. We have in mind the competition of Airbus and Boeing (or GM and Volkswagen) in a developing country. The host-country government endogeneizes tariffs, while Airbus and Boeing choose domestic output and FDI. Wages and employment in the home countries are bargained over between labor and management. We find that in the unique equilibrium, both Airbus and Boeing compete to undertake FDI in the developing country. This arises because the host country can play off the multinational corporations, which in turn stems from three factors: (a) Oligopolistic rivalry; (b) Quid prod quo FDI, which reduces tariffs; (c) Strategic outsourcing-FDI drives down the union wages at home if the host-country wage is sufficiently low. However, if the host-country wage is sufficiently high, then the union wage increases under FDI. In such cases, FDI competition benefits the multinationals, the labor unions as well as the host country. If Boeing undertakes FDI while Airbus does not, then: (i) Boeing's market share and profits are higher than Airbus's; (ii) the tariff facing Boeing is lower than that facing Airbus.FDI Competition, Quid Pro Quo FDI, Labor Union, Political Economy, Emerging Markets

Electroconvection in a dielectric liquid between two concentric half-cylinders with rigid walls: Linear and nonlinear analysis

We study the linear stability and nonlinear behavior of the electroconvection between two concentric halfcylinders with no-slip conditions on all boundaries. The no-slip condition makes impossible to apply the standard modal approach. Hence, we apply a finite element technique similar to the one we have used in a previous paper about the electroconvection in a rectangular enclosed domain. When compared to the classical problem of electroconvection between two full concentric cylinders, the linear criterion is higher, due to the viscous shear introduced by the lateral walls. As a consequence, the structure of the eigenmodes is very different. There is a repulsion between modeswith the same symmetry, forcing pairs of modes to cross each other repeatedly. For inner injection and small value of the ratio between the inner and outer radii the no-slip condition changes the nature of the bifurcation from subcritical to supercritical, while it is always subcritical for outer injection. To understand this behavior, we perform a modal analysis using the eigenfunctions obtained from the linear stability analysis as modal basis. We show that the supercritical branch is originated by the nonorthogonality of the modes when no-slip boundary conditions are imposed. These mechanism explains the previously unexplained appearance of the supercritical branch in the enclosed rectangular configuration.Ministerio de Economía y Competitividad FIS2014-54539-