What accounts for the changes in U.S. fiscal policy transmission?

Using vector autoregressions on U.S. time series for 1957-1979 and 1983-2004, we find government spending shocks to have stronger effects on output, consumption, and wages in the earlier sample. We try to account for this observation within a DSGE model featuring price rigidities and limited asset market participation. Specifically, we estimate the structural parameters of the model for both samples by matching impulse responses. Model-based counterfactual experiments suggest that increased asset market participation accounts for some of the changes in fiscal transmission. However, the key quantitative factor appears to be the more active monetary policy of the Volcker-Greenspan period. JEL Classification: E21, E62, E63Asset Market Participation, DSGE, Fiscal Policy, government spending, Minimum Distance Estimation, monetary policy, Vector autoregression

The VLQ Calorimeter of H1 at HERA: A Highly Compact Device for Measurements of Electrons and Photons under Very Small Scattering Angles

In 1998, the detector H1 at HERA has been equipped with a small backward spectrometer, the Very Low Q^2 (VLQ) spectrometer comprising a silicon tracker, a tungsten - scintillator sandwich calorimeter, and a Time-of-Flight system. The spectrometer was designed to measure electrons scattered under very low angles, equivalent to very low squared four - momentum transfers Q^2, and high energy photons with good energy and spatial resolution. The VLQ was in operation during the 1999 and 2000 run periods. This paper describes the design and construction of the VLQ calorimeter, a compact device with a fourfold projective energy read-out, and its performance during test runs and in the experiment.Comment: 32 pages, 25 figures, 2 tables (To be submitted to Nucl. Instrum. Meth. A

The dielectric clad axial slot antenna

Dieletric clad axial slot antenna

Faraday Rotation Spectroscopy of Quantum-Dot Quantum Wells

Time-resolved Faraday rotation studies of CdS/CdSe/CdS quantum-dot quantum wells have recently shown that the Faraday rotation angle exhibits several well-defined resonances as a function of probe energy close to the absorption edge. Here, we calculate the Faraday rotation angle from the eigenstates of the quantum-dot quantum well obtained with k.p theory. We show that the large number of narrow resonances with comparable spectral weight observed in experiment is not reproduced by the level scheme of a quantum-dot quantum well with perfect spherical symmetry. A simple model for broken spherical symmetry yields results in better qualitative agreement with experiment.Comment: 9 pages, 4 figure

A quasi-periodic oscillation in the blazar J1359+4011

The OVRO 40-m telescope has been monitoring the 15 GHz radio flux density of over 1200 blazars since 2008. The 15 GHz light curve of the flat spectrum radio quasar J1359+4011 shows a strong and persistent quasi-periodic oscillation. The time-scale of the oscillation varies between 120 and 150 days over a $\sim4$ year time span. We interpret this as the active galactic nucleus mass-scaled analog of low-frequency quasi-periodic oscillations from Galactic microquasars, or as evidence of modulation of the accretion flow by thermal instabilites in the "inner" accretion disc.Comment: 4 pages, 2 figures, 1 table. Accepted for publication in MNRAS Letter

First principles study of local electronic and magnetic properties in pure and electron-doped Nd2_2CuO4_4

The local electronic structure of Nd2CuO4 is determined from ab-initio cluster calculations in the framework of density functional theory. Spin-polarized calculations with different multiplicities enable a detailed study of the charge and spin density distributions, using clusters that comprise up to 13 copper atoms in the CuO2plane. Electron doping is simulated by two different approaches and the resulting changes in the local charge distribution are studied in detail and compared to the corresponding changes in hole doped La2CuO4. The electric field gradient (EFG) at the copper nucleus is investigated in detail and good agreement is found with experimental values. In particular the drastic reduction of the main component of the EFG in the electron-doped material with respect to LaCuO4 is explained by a reduction of the occupancy of the 3d3z^2-r^2 atomic orbital. Furthermore, the chemical shieldings at the copper nucleus are determined and are compared to results obtained from NMR measurements. The magnetic hyperfine coupling constants are determined from the spin density distribution

Exact bosonization for an interacting Fermi gas in arbitrary dimensions

We present an exact mapping of models of interacting fermions onto boson models. The bosons correspond to collective excitations in the initial fermionic models. This bosonization is applicable in any dimension and for any interaction between fermions. We show schematically how the mapping can be used for Monte Carlo calculations and argue that it should be free from the sign problem. Introducing superfields we derive a field theory that may serve as a new way of analytical study.Comment: Basic equations are derived more carefully and in a simpler wa

Characterisation of the PSI whole body counter by radiographic imaging

A joint project between the Paul Scherrer Institut (PSI) and the Institute of Radiation Physics was initiated to characterise the PSI whole body counter in detail through measurements and Monte Carlo simulation. Accurate knowledge of the detector geometry is essential for reliable simulations of human body phantoms filled with known activity concentrations. Unfortunately, the technical drawings provided by the manufacturer are often not detailed enough and sometimes the specifications do not agree with the actual set-up. Therefore, the exact detector geometry and the position of the detector crystal inside the housing were determined through radiographic images. X-rays were used to analyse the structure of the detector, and 60Co radiography was employed to measure the core of the germanium crystal. Moreover, the precise axial alignment of the detector within its housing was determined through a series of radiographic images with different incident angles. The hence obtained information enables us to optimise the Monte Carlo geometry model and to perform much more accurate and reliable simulation