The study of condensed matter by deep inelastic neutron scattering

This thesis describes the technique of electron-volt neutron spectroscopy at the pulsed spallation neutron source ISIS at the Rutherford Appleton Laboratory. A number of systems were studied, with the emphasis on the validity of the impulse approximation in each case. Assuming a Gaussian momentum distribution, the mean kinetic ener­gies of ZrHj, ZrD2, NbH and NbD and lithium metal between 20 K and 300 K were measured. By numerical calculation, it is shown that anharmonicity in metal hydride systems can be dealt with in terms of a Gaussian momentum distribution, as for har­monic systems. The vibrational density of states of H in ZrH2 was determined from inelastic neutron scattering measurements of the dynamic structure factor made on the MARI spectrometer, and used to perform exact numerical simulations of eVS mea­sured neutron Compton profiles for a range of momentum transfers. The deviations of these simulated data from the impulse approximation due to final state effects were compared to deviations from the impulse approximation of data measured on eVS. It is shown that these deviations are small enough to be treated by a straightforward correction procedure

The announcement effect: evidence from open market desk data : commentary

Paper for a conference sponsored by the Federal Reserve Bank of New York entitled Financial Innovation and Monetary TransmissionOpen market operations ; Monetary policy ; Federal Open Market Committee ; Federal funds market (United States)

Real-time Taylor rules and the federal funds futures market

This article compares movements in the federal funds rate from 1987 through 1997 with predictions from the federal funds market and a Taylor rule using unemployment and core CPI data. Although a Taylor rule using revised data does about as well as the futures market predictions, the best real-time predictions would have produced forecast errors about 50 percent larger than the futures data.Federal funds market (United States) ; Federal funds market (United States) ; Monetary policy

Metric perturbations from eccentric orbits on a Schwarzschild black hole: I. Odd-parity Regge-Wheeler to Lorenz gauge transformation and two new methods to circumvent the Gibbs phenomenon

We calculate the odd-parity, radiative ($\ell \ge 2$) parts of the metric perturbation in Lorenz gauge caused by a small compact object in eccentric orbit about a Schwarzschild black hole. The Lorenz gauge solution is found via gauge transformation from a corresponding one in Regge-Wheeler gauge. Like the Regge-Wheeler gauge solution itself, the gauge generator is computed in the frequency domain and transferred to the time domain. The wave equation for the gauge generator has a source with a compact, moving delta-function term and a discontinuous non-compact term. The former term allows the method of extended homogeneous solutions to be applied (which circumvents the Gibbs phenomenon). The latter has required the development of new means to use frequency domain methods and yet be able to transfer to the time domain while avoiding Gibbs problems. Two new methods are developed to achieve this: a partial annihilator method and a method of extended particular solutions. We detail these methods and show their application in calculating the odd-parity gauge generator and Lorenz gauge metric perturbations. A subsequent paper will apply these methods to the harder task of computing the even-parity parts of the gauge generator.Comment: 17 pages, 9 figures, Updated with one modified figure and minor changes to the text. Added DOI and Journal referenc

Gravitational perturbations and metric reconstruction: Method of extended homogeneous solutions applied to eccentric orbits on a Schwarzschild black hole

We calculate the gravitational perturbations produced by a small mass in eccentric orbit about a much more massive Schwarzschild black hole and use the numerically computed perturbations to solve for the metric. The calculations are initially made in the frequency domain and provide Fourier-harmonic modes for the gauge-invariant master functions that satisfy inhomogeneous versions of the Regge-Wheeler and Zerilli equations. These gravitational master equations have specific singular sources containing both delta function and derivative-of-delta function terms. We demonstrate in this paper successful application of the method of extended homogeneous solutions, developed recently by Barack, Ori, and Sago, to handle source terms of this type. The method allows transformation back to the time domain, with exponential convergence of the partial mode sums that represent the field. This rapid convergence holds even in the region of $r$ traversed by the point mass and includes the time-dependent location of the point mass itself. We present numerical results of mode calculations for certain orbital parameters, including highly accurate energy and angular momentum fluxes at infinity and at the black hole event horizon. We then address the issue of reconstructing the metric perturbation amplitudes from the master functions, the latter being weak solutions of a particular form to the wave equations. The spherical harmonic amplitudes that represent the metric in Regge-Wheeler gauge can themselves be viewed as weak solutions. They are in general a combination of (1) two differentiable solutions that adjoin at the instantaneous location of the point mass (a result that has order of continuity $C^{-1}$ typically) and (2) (in some cases) a delta function distribution term with a computable time-dependent amplitude.Comment: 25 pages, 5 figures, Updated with minor change

Data revisions and the identification of monetary policy shocks

Monetary policy research using time series methods has been criticized for using more information than the Federal Reserve had available in setting policy. To quantify the role of this criticism, we propose a method to estimate a VAR with real-time data while accounting for the latent nature of many economic variables, such as output. Our estimated monetary policy shocks are closely correlated with a typically estimated measure. The impulse response functions are broadly similar across the methods. Our evidence suggests that the use of revised data in VAR analyses of monetary policy shocks may not be a serious limitation.Monetary policy

Soft landings on a bumpy runway

Our case study of the 1995 economic slowdown reveals that part of the widespread deterioration in economic indicators was predictable in light of 1994 monetary policy actions. But it was also partly unanticipated due to a modest adverse supply shock in the first quarter of 1995.Monetary policy - United States ; Monetary policy ; Recessions

Economic determinants of the nominal treasury yield curve

We study the effect of different types of macroeconomic impulses on the nominal yield curve. We employ two distinct approaches to identifying economic shocks in VARs. Our first approach uses a structural VAR due to Galí (1992). Our second strategy identifies fundamental impulses from alternative empirical measures of economic shocks proposed in the literature. We find that most of the long-run variability of interest rates of all maturities is driven by macroeconomic impulses. Shocks to preferences for current consumption consistently induce large, persistent, and statistically significant shifts in the level of the yield curve. In contrast, technology shocks induce weaker and less robust patterns of interest rate responses, since they move real rates and expected inflation in opposite directions. Monetary policy shocks are the only macroeconomic shocks with a consistent and significant impact on the slope of the yield curve. We find no evidence that fiscal policy shocks induce any significant interest rate responses.Macroeconomics ; Monetary policy ; Fiscal policy

Trumpet Initial Data for Boosted Black Holes

We describe a procedure for constructing initial data for boosted black holes in the moving-punctures approach to numerical relativity that endows the initial time slice from the outset with trumpet geometry within the black hole interiors. We then demonstrate the procedure in numerical simulations using an evolution code from the Einstein Toolkit that employs 1+log slicing. The Lorentz boost of a single black hole can be precisely specified and multiple, widely separated black holes can be treated approximately by superposition of single hole data. There is room within the scheme for later improvement to re-solve (iterate) the constraint equations in the multiple black hole case. The approach is shown to yield an initial trumpet slice for one black hole that is close to, and rapidly settles to, a stationary trumpet geometry. Initial data in this new approach is shown to contain initial transient (or "junk") radiation that is suppressed by as much as two orders of magnitude relative to that in comparable Bowen-York initial data.Comment: 18 pages, 18 figure