Origins of the H, He I, and Ca II Line Emission in Classical T Tauri Stars

We perform local excitation calculations to obtain line opacities and emissivity ratios and compare them with observed properties of H, He I, O I, Ca II, and Na I lines to determine the density, temperature, and photon ionization rate. We find that UV photoionization is the most probable excitation mechanism for generating the He I 10830 opacities that produce all the associated absorption features. We also calculate the specific line flux at an observed velocity of v_obs = +/- 150 km/s for both radial wind and infall models. All the model results, together with observed correlations between absorption and emission features and between narrow and broad emission components, are used to deduce the origins of the strong H, He I, and Ca II broad line emission. We conclude that the first two arise primarily in a radial outflow that is highly clumpy. The bulk of the wind volume is filled by gas at a density ~10^9 cm^-3 and optically thick to He I 10830 and H alpha, but optically thin to He I 5876, Pa gamma, and the Ca II infrared triplet. The optically thick He I 5876 emission occurs mostly in regions of density greater than or equal to 10^11 cm^-3 and temperature greater than or equal to 1.5x10^4 K, while the optically thick H alpha and Pa gamma emission occur mostly in regions of density around 10^11 cm^-3 and temperature between 8750 and 1.25x10^4 K. In producing the observed line fluxes at a given v_obs, the covering factor of these emission clumps is sufficiently small not to incur significant absorption of the stellar and veiling continua in either He I or H lines. The strong Ca II broad line emission likely arises in both the magnetospheric accretion flow and the disk boundary layer, where the gases dissipate part of their rotational energies before infalling along magnetic field lines. The needed density and temperature are ~10^12 cm^-3 and less than or equal to 7500 K.Comment: Accepted to MNRAS, 88 pages, 24 figure

Inflation and the poor

Using polling data for 31,869 households in 38 countries, and allowing for country effects, the authors show that the poor are more likely than the rich to mention inflation as a top national concern. This result survives several robustness checks. Also, direct measures of improvements in well-being for the poor - the change in their share of national income, the percentage decline in poverty, and the percentage change in the real minimum wage - are negatively correlated with inflation in pooled cross-country samples. High inflation tends to lower the share of the bottom quintile and the real minimum wage - and tends to increase poverty.Economic Theory&Research,Environmental Economics&Policies,Economic Conditions and Volatility,Payment Systems&Infrastructure,Health Indicators,Inflation,,Environmental Economics&Policies,Economic Theory&Research,Economic Conditions and Volatility

The Soviet economic decline : historical and republican data

Soviet growth for 1960-89 was the worst in the world, after controlling for investment and human capital. And relative performance worsens over time. The authors explain the declining Soviet growth rate from 1950 to 1987 by the declining marginal product of capital. The rate of total factor productivity growth is roughly constant over that period. Although the Soviet slowdown has conventionally been attributed to extensive growth (rising capital-to-output ratios), extensive growth is also a feature of market-oriented economies like Japan and Korea. One message from the authors'results could be that Soviet-style stagnation awaits other countries that have relied on extensive growth. The Soviet experience can be read as a particularly extreme dramatization of the long-run consequences of extensive growth. What led to the relative Soviet decline was a low elasticity of substitution between capital and labor, which caused diminishing returns to capital to be especially acute. (The natural question to ask is why Soviet capital-labor substitution was more difficult than in Western market economies, and whether this difficulty was related to the Soviets'planned economic systems.) Tentative evidence indicates that the burden of defense spending also contributed to the Soviet debacle. Differences in growth performance between the Soviet republics are explained by the same factors that figure in the empirical cross-section growth literature: initial income, human capital population growth, and the degree of sectoral distortions. The results the authors got with the Soviet Union in the international cross-section itself was disastrous for long-run economic growth in the Soviet Union. This point may now seem obvious but was not so apparent in the halcyon days of the 1950s, when the Soviet case was often cited as support for the neoclassical model's prediction that distortions do not have steady state growth effects. Since a heavy degree of planning and government intervention exists in many countries, especially developing countries, the ill-fated Soviet experience continues to be of interest.Economic Growth,Economic Theory&Research,Achieving Shared Growth,Governance Indicators,Health Monitoring&Evaluation

How Large Are the Welfare Gains from Technological Innovation Induced by Environmental Policies?

This paper examines whether the welfare gains from technological innovation that reduces future abatement costs are larger or smaller than the “Pigouvian” welfare gains from optimal pollution control. The relative welfare gains from innovation depend on three key factors: the initially optimal level of abatement, the speed at which innovation reduces future abatement costs, and the discount rate. We calculate the welfare gains from innovation under a variety of different scenarios. Mostly they are less than the Pigouvian welfare gains. To be greater, innovation must reduce abatement costs substantially and quickly and the initially optimal abatement level must be fairly modest.innovation, welfare, regulation, endogenous, technological, change, R&D

Redshifted Absorption at He I 10830 as a Probe of the Accretion Geometry of T Tauri Stars

We probe the geometry of magnetospheric accretion in classical T Tauri stars by modeling red absorption at He I 10830 via scattering of the stellar and veiling continua. Under the assumptions that the accretion flow is an azimuthally symmetric dipole and helium is sufficiently optically thick that all incident 1-micron radiation is scattered, we illustrate the sensitivity of He I 10830 red absorption to both the size of the magnetosphere and the filling factor of the hot accretion shock. We compare model profiles to those observed in 21 CTTS with subcontinuum redshifted absorption at He I 10830 and find that about half of the stars have red absorptions and 1-micron veilings that are consistent with dipole flows of moderate width with accretion shock filling factors matching the size of the magnetospheric footpoints. However, the remaining 50% of the profiles, with a combination of broad, deep absorption and low 1-micron veiling, require very wide flows where magnetic footpoints are distributed over 10-20% of the stellar surface but accretion shock filling factors are < 1%. We model these profiles by invoking large magnetospheres dilutely filled with accreting gas, leaving the disk over a range of radii in many narrow "streamlets" that fill only a small fraction of the entire infall region. In some cases accreting streamlets need to originate in the disk between several stellar radii and at least the corotation radius. A few stars have such deep absorption at velocities greater than half the stellar escape velocity that flows near the star with less curvature than a dipole trajectory seem to be required.Comment: 26 pages, emulateapj format, Accepted by ApJ, to appear 2008 November 1

How Large Are the Welfare Gains from Technological Innovation Induced by Environmental Policies?

This paper examines whether the welfare gains from technological innovation that reduces future abatement costs are larger or smaller than the “Pigouvian” welfare gains from optimal pollution control. The relative welfare gains from innovation depend on three key factors - the initially optimal level of abatement, the speed at which innovation reduces future abatement costs, and the discount rate. We calculate the welfare gains from innovation under a variety of different scenarios. Mostly they are less than the Pigouvian welfare gains. To be greater, innovation must reduce abatement costs substantially and quickly and the initially optimal abatement level must be fairly modest.innovation, welfare, regulation, endogenous, technological, change, R&D

Instrument Choice for Environmental Protection When Technological Innovation is Endogenous

This paper presents an analytical and numerical comparison of the welfare impacts of alternative instruments for environmental protection in the presence of endogenous technological innovation. We analyze emissions taxes and both auctioned and free (grandfathered) emissions permits. We find that under different sets of circumstances each of the three policies may induce a significantly higher welfare gain than the other two policies. In particular, the relative ranking of policy instruments can crucially depend on the ability of adopting firms to imitate the innovation, the costs of innovation, the slope and level of the marginal environmental benefit function, and the number of firms producing emissions. Moreover, although in theory the welfare impacts of policies differ in the presence of innovation, sometimes these differences are relatively small. In fact, when firms anticipate that policies will be adjusted over time in response to innovation, certain policies can become equivalent. Our analysis is simplified in a number of respects; for example, we assume homogeneous and competitive firms. Nonetheless, our preliminary results suggest there is no clear-cut case for preferring any one policy instrument on the grounds of dynamic efficiency.

How Important is Technological Innovation in Protecting the Environment?

Economists have speculated that the welfare gains from technological innovation that reduces the future costs of environmental protection could be a lot more important than the "Pigouvian" welfare gains over time from correcting a pollution externality. If so, then a primary concern in the design of environmental policies should be the impact on induced innovation, and a potentially strong case could be made for additional instruments such as research subsidies. This paper examines the magnitude of the welfare gains from innovation relative to the discounted Pigouvian welfare gains, using a dynamic social planning model in which research and development (R&D) augments a knowledge stock that reduces future pollution abatement costs. We find that the discounted welfare gains from innovation are typically smaller....and perhaps much smaller....than the discounted Pigouvian welfare gains. This is because the long-run gain to innovation is bounded by the maximum reduction in abatement costs and, since R&D is costly, it takes time to accumulate enough knowledge to substantially reduce abatement costs. Only in cases when innovation substantially reduces abatement costs quickly (by roughly 50% within 10 years) and the Pigouvian amount of abatement is initially modest, can the welfare gains from innovation exceed the welfare gains from pollution control. These results apply for both flow and stock pollutants, and for linear and convex environmental damage functions. Our results suggest that spurring technological innovation should not be emphasized at the expense of achieving the optimal amount of pollution control. More generally, our results appear to have implications for a broad range of policy issues. They suggest that the welfare gains from innovation that reduces the costs of supplying any public good (defense, crime prevention, infrastructure, etc.) may be fairly small relative to those from providing the optimal amount of the public good over time.