Real-time electron dynamics with exact-exchange time-dependent density-functional theory

The exact exchange potential in time-dependent density-functional theory is defined as an orbital functional through the time-dependent optimized effective potential (TDOEP) method. We numerically solve the TDOEP integral equation for the real-time nonlinear intersubband electron dynamics in a semiconductor quantum well with two occupied subbands. By comparison with adiabatic approximations, it is found that memory effects in the exact exchange potential become significant when the electron dynamics takes place in the vicinity of intersubband resonances.Comment: 5 pages, 5 figure

Coherent control of intersubband optical bistability in quantum wells

We present a study of the nonlinear intersubband (ISB) response of conduction electrons in a GaAs/AlGaAs quantum well to strong THz radiation, using a density-matrix approach combined with time-dependent density-functional theory. We demonstrate coherent control of ISB optical bistability, using THz control pulses to induce picosecond switching between the bistable states. The switching speed is determined by the ISB relaxation and decoherence times, T1 and T2.Comment: 3 pages, 3 figure

Has the Accuracy of German Macroeconomic Forecasts Improved?

This paper asks whether the accuracy of German macroeconomic forecasts has improved over time. We examine one-year-ahead forecasts of rates of real GDP growth and inflation for the years 1967 to 2010 by three major German forecasters and the OECD. We find that overall error levels are high but not much different from those for the U.S. and U.K. In the 1980s and 1990s accuracy improved somewhat, but has now returned to its 1970s level, indicating that it reflects the variance of growth and inflation. Benchmark comparisons of these predictions with ex post forecasts of a macroecono-metric model indicate that accuracy can be improved but it will be difficult to achieve.Forecast evaluations; macroeconomic forecasting; accuracy limits

Has the accuracy of German macroeconomic forecasts improved?

The major focus of this paper is to determine whether the accuracy of German macroeconomic forecasts has improved over time. We examine 1-year-ahead forecasts of real GDP and inflation for 1967 to 2001 made by three major German forecasting groups and the OECD. We examine the accuracy of the forecasts over the entire period and in three sub-periods. We conclude that, with some exceptions, the errors of the German forecasters were similar to those of their US and UK counterparts. While the absolute size of the forecast errors has declined, this is not the case for relative accuracy. A benchmark comparison of these predictions with the ex post forecasts of a macroeconometric model indicates that the quality of the growth forecasts can be improved but that the expected increase in accuracy may not be substantial. --Forecast evaluations,macroeconomic forecasting,accuracy limits

Time-dependent Kohn-Sham theory with memory

In time-dependent density-functional theory, exchange and correlation (xc) beyond the adiabatic local density approximation can be described in terms of viscoelastic stresses in the electron liquid. In the time domain, this leads to a velocity-dependent xc vector potential with a memory containing short- and long-range components. The resulting time-dependent Kohn-Sham formalism describes the dynamics of electronic systems including decoherence and relaxation. For the example of collective charge-density oscillations in a quantum well, we illustrate the xc memory effects, clarify the dissipation mechanism, and extract intersubband relaxation rates for weak and strong excitations.Comment: 4 pages, 4 figure

Effect of Alternative Wheat and Feed Grain Prices on Optimum Farm Plans and Income in Central South Dakota: Aurora, Brule, Charles Mix, Gregory and Jerauld Counties

The purpose of this report is to present some results of a cooperative research project between the South Dakota Agricultural Experiment Station and the Farm Production Economics Division, Economic Research Service, U. S. Department of Agriculture. This research contributes to a larger project-GP-5, Economic Problems in the Production and Marketing of Great Plains Wheat. The general objectives of the research undertaken in South Dakota were: ( 1) To provide economic data needed by farmers to make profitable adjustments in their farming systems and production practices and (2) To develop a research background for evaluating Government farm programs under varying assumptions

Effect of Alternative Wheat and Feed Grain Prices on Optimum Farm Plans and Income in Cetnral South Dakota: Brown and Spink Counties

The purpose of this report is to present some results of a cooperative research project between the South Dakota Agricultural Experiment Station and the Farm Production Economics Division, Economic Research Service, U. S. Department of Agriculture. This research contributes· to a larger project-GP-5, Economic Problems in the Production and Marketing of Great Plains Wheat. The general objectives of the research undertaken in South Dakota were: (1) to provide economic data needed by farmers to make profitable adjustments in their farming systems and production practices and (2) to develop a research background for evaluating government farm programs under varying assumptions

Effect of Alternative Wheat and Feed Grain Prices on Optimum Farm Plans and Income: Beadle, Clark, Codington, Day, Marshall and Roberts Counties

The purpose of this report is to present some results of a cooperative research project between the South Dakota Agricultural Experiment Station and the Farm Production Economics Division, Economic Research Service, U. S. Department of Agriculture. This research contributes to a larger project-GP-5, Economic Problems in the Production and Marketing of Great Plains Wheat. The general objectives of the research undertaken in South Dakota were: (1) to provide economic data needed by farmers to make profitable adjustments in their farming systems and production practices and (2) to develop a research background for evaluating government farm programs under varying assumptions

Effect of Alternative Wheat and Feed Grain Prices on Optimum Farm Plans and Income in Central South Dakota: Buffalo, Hand and Hyde Counties

The purpose of this report is to present some results of a cooperative research project between the South Dakota Agricultural Experiment Station and the Farm Production Economics Division, Economic Research Service, U. S. Department of Agriculture. This research contributes to a larger project-GP-5, Economic Problems in the Production and Marketing of Great Plains Wheat. The general objectives of the research undertaken in South Dakota were (1) To provide economic data needed by farmers to make profitable adjustments in their farming systems and production practices and (2) To develop a research background for evaluating Government farm programs under varying assumptions

Effect of Alternative Wheat and Feed Grain Prices on Optimum Farm Plans and Income in Central South Dakota: Hughes and Sully Counties

The purpose of this report is to present some results of a cooperative research project between the South Dakota Agricultural Experiment Station and the Farm Production Economics Division, Economic Research Service, U. S. Department of Agriculture. This research contributes to a larger project-GP-5, Economic Problems in the Production and Marketing of Great Plains Wheat. The general objectives of the research undertaken in South Dakota were: (1) To provide economic data needed by farmers to make profitable adjustments in their farming systems and production practices and (2) To develop a research background for evaluating Government farm programs under varying assumptions