Relaxation rates of the linearized Uehling-Uhlenbeck equation for bosons

We linearize the Uehling-Uhlenbeck equation for bosonic gases close to thermal equilibrium under the assumption of a contact interaction characterized by a scattering length a. We show that the spectrum of relaxation rates is similar to that of a classical hard-sphere gas. However, the relaxation rates show a significant dependence on the fugacity z of the gas, increasing by as much as 60% of their classical value for z approaching 1. The relaxation modes are also significantly altered at higher values of z. The relaxation rates and modes are determined by the eigenvalues and eigenvectors of a Fredholm integral operator of the second kind. We derive an analytical form for the kernel of this operator and present numerical results for the first few eigenvalues and eigenvectors.Robert A. Welch Foundation F-1051Physic

The expectations trap hypothesis

This article explores a hypothesis about the take-off in inflation in the early 1970s. According to the expectations trap hypothesis, the Fed was driven to high money growth by a fear of violating the expectations of high inflation that existed at the time. The authors argue that this hypothesis is more compelling than the Phillips curve hypothesis, according to which the Fed produced the high inflation as an unfortunate by product of a conscious decision to jump start a weak economy.Inflation (Finance) ; Phillips curve

The expectations trap hypothesis

The authors examine the inflation take-off of the early 1970s in terms of the expectations trap hypothesis, according to which fear of violating the public’s inflation expectations pushed the Fed into producing high inflation. This interpretation is compared with the Phillips curve hypothesis, according to which the Fed produced high inflation as the unfortunate byproduct of a conscious decision to jump-start a weak economy. Which hypothesis is more plausible has important implications for what should be done to prevent future inflation flare-ups.Inflation (Finance) ; Phillips curve ; Economic conditions - United States

How does dissipation affect the transition from static to dynamic macroscopic friction?

Description of the transitional process from a static to a dynamic frictional regime is a fundamental problem of modern physics. Previously we developed a model based on the well-known Frenkel-Kontorova model to describe dry macroscopic friction. Here this model has been modified to include the effect of dissipation in derived relations between the kinematic and dynamic parameters of a transition process. The main (somewhat counterintuitive) result is a demonstration that the rupture (i.e. detachment front) velocity of the slip pulse which arises during the transition does not depend on friction. The only parameter (besides the elastic and plastic properties of the medium) controlling the rupture velocity is the shear to normal stress ratio. In contrast to the rupture velocity, the slip velocity does depend on friction. The model we have developed describes these processes over a wide range of rupture and slip velocities (up to 7 orders of magnitude) allowing, in particular, the consideration of seismic events ranging from regular earthquakes, with rupture velocities on the order of a few km/s, to slow slip events, with rupture velocities of a few km/day.Comment: 21 pages, 12 figure

SIGMA: A New Open Economy Model for Policy Analysis

In this paper, we describe a new multicountry open economy SDGE model named "SIGMA" that we have developed as a quantitative tool for policy analysis. We compare SIGMA's implications to those of an estimated large-scale econometric policy model (the FRB/Global model) for an array of shocks that are often examined in policy simulations. We show that SIGMA's implications for the near-term responses of key variables are generally similar to those of FRB/Global. Nevertheless, some quantitative disparities between the two models remain due to certain restrictive aspects of SIGMA's optimization-based framework. We conclude by using long-term simulations to illustrate some areas of comparative advantage of our SDGE modeling framework.

Taylor rules in a limited participation model

The authors use the limited participation model of money to study Taylor rules' operating characteristics for setting the interest rate. Rules are evaluated according to their ability to protect the economy from bad outcomes like the burst of inflation observed in the 1970s. On the basis of their analysis, the authors argue for a rule that 1) raises the nominal interest rate more than one-for-one with a rise in inflation; and 2) does not change the interest rate in response to a change in output relative to trend.Monetary policy ; Interest rates

The adjustment of global external balances: does partial exchange rate pass-through to trade prices matter?

This paper assesses whether partial exchange rate pass-through to trade prices has important implications for the prospective adjustment of global external imbalances. To address this question, we develop and estimate an open-economy DGE model in which pass-through is incomplete due to the presence of local currency pricing, distribution services, and a variable demand elasticity that leads to fluctuations in optimal markups. We find that the overall magnitude of trade adjustment is similar in a low and high pass-through world with more adjustment in a low pass-world occurring through a larger response of the exchange rate and terms of trade rather than real trade flows.Foreign exchange rates ; Imports - Prices

Monetary policy in a financial crisis

What are the economic effects of an interest rate cut when an economy is in the midst of a financial crisis? Under what conditions will a cut stimulate output and employment, and raise welfare? Under which will it have the opposite effects? The authors answer these questions in a general class of open-economy models, modeling a financial crisis as a time when collateral constraints are suddenly binding. They find that when there are frictions in adjusting the level of output in the traded goods sector and the rate at which that output can be used in other parts of the economy, a cut in the interest rate is most likely to result in a welfare-reducing drop in output and employment. When these frictions are absent, a cut in the interest rate improves asset positions and promotes a welfare-increasing economic expansion.Financial crises ; Monetary policy ; Interest rates

Model of deep non-volcanic tremor part I: ambient and triggered tremor

There is evidence of triggering of tremor by seismic waves emanating from distant large earthquakes. The frequency contents of triggered and ambient tremor are largely identical, suggesting that tremor does not depend directly on the nature of the source. We show here that the model of plate dynamics developed earlier by us is an appropriate tool for describing the onset of tremor. In the framework of this model, tremor is an internal response of a fault to a failure triggered by external disturbances. The model predicts generation of radiation in a frequency range defined by the fault parameters. Other specific features predicted are: the upper limit of the size of the emitting area is a few dozen km; tremor accompanies earthquakes and aseismic slip; the frequency content of tremor depends on the type of failure. The model also explains why a tremor has no clear impulsive phase, in contrast to earthquakes. A comparatively small effective normal stress (hence a high fluid pressure) is required to make the model consistent with observed tremor parameters. Our model indicates that tremor is not necessarily a superposition of low frequency earthquakes, as commonly assumed, although the latter may trigger them. The approach developed complements the conventional viewpoint which assumes that tremor reflects a frictional process with low rupture speed. Essentially our model adds the hypothesis that resonant-type oscillations exist inside a fault. This addition may change our understanding of the nature of tremor in general, and the methods of its identification and location in particular.Comment: 32 pages, 16 figures. arXiv admin note: text overlap with arXiv:1202.091