A new comparative approach to macroeconomic modeling and policy analysis

In the aftermath of the global financial crisis, the state of macroeconomic modeling and the use of macroeconomic models in policy analysis has come under heavy criticism. Macroeconomists in academia and policy institutions have been blamed for relying too much on a particular class of macroeconomic models. This paper proposes a comparative approach to macroeconomic policy analysis that is open to competing modeling paradigms. Macroeconomic model comparison projects have helped produce some very influential insights such as the Taylor rule. However, they have been infrequent and costly, because they require the input of many teams of researchers and multiple meetings to obtain a limited set of comparative findings. This paper provides a new approach that enables individual researchers to conduct model comparisons easily, frequently, at low cost and on a large scale. Using this approach a model archive is built that includes many well-known empirically estimated models that may be used for quantitative analysis of monetary and fiscal stabilization policies. A computational platform is created that allows straightforward comparisons of models’ implications. Its application is illustrated by comparing different monetary and fiscal policies across selected models. Researchers can easily include new models in the data base and compare the effects of novel extensions to established benchmarks thereby fostering a comparative instead of insular approach to model development

The East End, the West End, and King's Cross: On Clustering in the Four-Player Hotelling Game

We study experimentally a standard four-player Hotelling game, with a uniform density of consumers and inelastic demand. The pure strategy Nash equilibrium configuration consists of two firms located at one quarter of the ``linear city'', and the other two at three quarters. We do not observe convergence to such an equilibrium. In our experimental data we find three clusters. Besides the direct proximity of the two equilibrium locations this concerns the focal mid-point. Moreover, we observe that whereas this mid-point appears to become more notable over time, other focal points fade away. We explain how these observations are related to best-response dynamics, and to the fact that the players rely on best-responses in particular when they are close to the equilibrium configuration.Location model, Nonconvergence, Focal point, Best-response dynamics

New Keynesian versus old Keynesian government spending multipliers

Renewed interest in fiscal policy has increased the use of quantitative models to evaluate policy. Because of modeling uncertainty, it is essential that policy evaluations be robust to alternative assumptions. We find that models currently being used in practice to evaluate fiscal policy stimulus proposals are not robust. Government spending multipliers in an alternative empirically-estimated and widely-cited new Keynesian model are much smaller than in these old Keynesian models; the estimated stimulus is extremely small with GDP and employment effects only one-sixth as large

Second-harmonic phonon spectroscopy of α\alpha-quartz

We demonstrate midinfrared second-harmonic generation as a highly sensitive phonon spectroscopy technique that we exemplify using $\alpha$-quartz (SiO$_2$) as a model system. A midinfrared free-electron laser provides direct access to optical phonon resonances ranging from $350\ \mathrm{cm}^{-1}$ to $1400\ \mathrm{cm}^{-1}$. While the extremely wide tunability and high peak fields of an free-electron laser promote nonlinear spectroscopic studies---complemented by simultaneous linear reflectivity measurements---azimuthal scans reveal crystallographic symmetry information of the sample. Additionally, temperature-dependent measurements show how damping rates increase, phonon modes shift spectrally and in certain cases disappear completely when approaching$T_c=846\ \mathrm{K}$where quartz undergoes a structural phase transition from trigonal$\alpha$-quartz to hexagonal$\beta$-quartz, demonstrating the technique's potential for studies of phase transitions

Optimizing A New Flow Diversion Structure For The Planned Expanding Of The Spillway For The Malter Dam In Germany Using A Physical Hydraulic Model

The State Reservoir Administration of Saxony is planning to expand the spillway discharge capacity of the 102-year-old Malter Dam. After a catastrophic flood in 2002, updated hydrologic modeling indicated that the design discharges for the dam had increased significantly. As a result, the original spillway discharge capacity was insufficient to pass the revised design flows. A design concept was developed to add a second spillway and stilling basin to the dam, and to pass flow into this spillway using a novel vertical flow separator. The design and performance of this system was evaluated using a 1:25-scale physical model. The modeling activities were performed by the Research Institute for Water and Environment located at the University of Siegen. The modeling effort led to an improved design of the vertical flow separator which meets the needs of the project and will allow for an increase in the spillway discharge capacity to satisfy dam safety concerns

Covariant boost and structure functions of baryons in Gross-Neveu models

Baryons in the large N limit of two-dimensional Gross-Neveu models are reconsidered. The time-dependent Dirac-Hartree-Fock approach is used to boost a baryon to any inertial frame and shown to yield the covariant energy-momentum relation. Momentum distributions are computed exactly in arbitrary frames and used to interpolate between the rest frame and the infinite momentum frame, where they are related to structure functions. Effects from the Dirac sea depend sensitively on the occupation fraction of the valence level and the bare fermion mass and do not vanish at infinite momentum. In the case of the kink baryon, they even lead to divergent quark and antiquark structure functions at x=0.Comment: 13 pages, 12 figures; v2: minor correction

A conduction-cooled, 680-mm-long warm bore, 3-T Nb3Sn solenoid for a Cerenkov free electron laser

A compact, cryocooler cooled Nb3Sn superconducting magnet system for a Cerenkov free electron laser has been designed, fabricated and tested. The magnet is positioned directly behind the electron gun of the laser system. The solenoidal field compresses and guides a tube-shaped 100 A, 500 kV electron beam. A two-stage GM cryocooler, equipped with a first generation ErNi5 regenerator, cools the epoxy impregnated solenoid down to the operating temperature of about 7.5 K. This leaves a conservative operational margin for the MJR type of Nb3Sn conductor of about 350% (I c) at 3T. Current leads with HTS sections between the first and second stage of the cryocooler effectively reduce the conductive heat leak. In the warm bore, 60 mm in diameter and 680 mm long, an operational magnetic field of 2 T has been achieved during laser operation without any quench. The field homogeneity is better than 99.5% over 450 mm axial length. Design details and test results of this magnet system are presented