Learning by Doing vs Learning by Researching in a Model of Climate Change Policy Analysis

Many predictions and conclusions in climate change literature have been made on the basis of theoretical analyses and quantitative models that assume exogenous technological change. One may wonder if those policy prescriptions hold in the more realistic case of endogenously evolving technologies. In previous work we modified a popular integrated assessment model to allow for an explicit role of the stock of knowledge which accumulates through R&D investment. In our formulation knowledge affects the output production technology and the emission-output ratio. In this paper we make progress in our efforts aimed to model the process of technological change. In keeping with recent theories of endogenous growth, we specify two ways in which knowledge accumulates: via a deliberate, optimally selected R&D decision or via experience, giving rise to Learning by Doing. We simulate the model under the two versions of endogenous technical change and look at the dynamics of a number of relevant variables.Climate Policy, Environmental Modeling, Integrated Assessment, Technical Change

Fixed-Connectivity Membranes

The statistical mechanics of flexible surfaces with internal elasticity and shape fluctuations is summarized. Phantom and self-avoiding isotropic and anisotropic membranes are discussed, with emphasis on the universal negative Poisson ratio common to the low-temperature phase of phantom membranes and all strictly self-avoiding membranes in the absence of attractive interactions. The study of crystalline order on the frozen surface of spherical membranes is also treated.Comment: Chapter 11 in "Statistical mechanics of Membranes and Surfaces", ed. by D.R. Nelson, T. Piran and S. Weinberg (World Scientific, Singapore, 2004); 25 pages with 26 figures (high resolution figures available from author

On the Economics of Regional Powers: Comparing China, India, Brazil, and South Africa

As the conception of and debates on regional powers have been led by political science, this pa-per aims to contribute to the discussion from an economics perspective. Based on the discussion of different concepts of economic power—such as those of Schumpeter, Perroux, Predöhl, or Kindleberger—concepts of technological leadership, and the global value chain approaches, the paper develops a research framework for the economics of regional powers. This framework is then tested using descriptive statistics as well as regressions analysis, with a focus on the four regional powers Brazil, China, India, and South Africa. As economic power is relational, the re-lationship of regional powers to other nations in the region is analyzed. According to the findings, only limited statements on the economics of regional powers are possible: a regional power can be described as an economy with a relatively large population and land area which plays a dominant role in trade within the region and in the regional governance. The regional power develops its technological capacities, and its businesses act regionally and globally with increasing strength.Brazil, China, economic geography, economic leadership, economic power, growth, India, investment, public goods, regional powers, regression analysis, South Africa, technological change, value chain, trade.

Technological change in economic models of environmental policy: a survey

This paper provides an overview of the treatment of technological change in economic models of environmental policy. Numerous economic modeling studies have confirmed the sensitivity of mid- and long-run climate change mitigation cost and benefit projections to assumptions about technology costs. In general, technical progress is considered to be a noneconomic, exogenous variable in global climate change modeling. However, there is overwhelming evidence that technological change is not an exogenous variable but to an important degree endogenous, induced by needs and pressures. Hence, some environmenteconomy models treat technological change as endogenous, responding to socio-economic variables. Three main elements in models of technological innovation are: (i) corporate investment in research and development, (ii) spillovers from R&D, and (iii) technology learning, especially learning-by-doing. The incorporation of induced technological change in different types of environmental-economic models tends to reduce the costs of environmental policy, accelerates abatement and may lead to positive spillover and negative leakage. --exogenous technological change,induced technological change,environmenteconomy models

Observation of the semileptonic decays B ---> D* tau- anti-nu(tau) and evidence for B ---> D tau- anti-nu(tau

We present measurements of the semileptonic decays B- --> D0 tau- nubar, B- --> D*0 tau- nubar, B0bar --> D+ tau- nubar, and B0bar --> D*+ tau- nubar, which are potentially sensitive to non--Standard Model amplitudes. The data sample comprises 232x10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector. From a combined fit to B- and B0bar channels, we obtain the branching fractions B(B --> D tau- nubar) = (0.86 +/- 0.24 +/- 0.11 +/- 0.06)% and B(B --> D* tau- nubar) = (1.62 +/- 0.31 +/- 0.10 +/- 0.05)% (normalized for the B0bar), where the uncertainties are statistical, systematic, and normalization-mode-related

Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays

We present measurements of the branching fractions for the three-body decays B0 -> D(*)-/+ K0 pi^+/-$and their resonant submodes$B0 -> D(*)-/+ K*+/- using a sample of approximately 88 million BBbar pairs collected by the BABAR detector at the PEP-II asymmetric energy storage ring. We measure: B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4} B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4} From these measurements we determine the fractions of resonant events to be : f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) = 0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let