966 research outputs found
Search, Costly Price Adjustment and the Frequency of Price Changes - Theory and Evidence
We establish a new empirical finding that the intensity of search for the best price affects the frequency of nominal price changes. This relationship holds in very different economies and for various proxies for search intensity. We derive this relationship from a model of monopolistically competitive firms that face menu costs of changing nominal prices and heterogeneous consumers who search for the best price. We discuss alternative explanations and argue that they do not explain the observed correlations. Our results establish that pricing policies differ endogenously in the cross-section. This may be an important feature missing in many macroeconomic models based on nominal rigidities with exogenous frequency of price changes.Nominal rigidity; search; price adjustment
Regular Adjustment - Theory and Evidenc
We ask why, in many circumstances and many environments, decision-makers choose to act on a time-regular basis (e.g. adjust every six weeks, etc.) or on a state-regular basis (e.g. change an interest rate by 0.25%, etc.), even though such an approach appears suboptimal. The paper attributes regular behaviour to adjustment cost heterogeneity. The reasons for this heterogeneity are discussed. We show that, given the cost heterogeneity, the likelihood of adopting regular policies depends on the shape of the benefit function: the flatter it is, the more likely, ceteris paribus, is regular adjustment. In general, however, there is no clear relationship between the degree of cost and benefit function heterogeneity and the incidence of regular adjustment. We provide sufficient conditions under which the less frequent are adjustments, the greater is the incidence of regular policies. To test the model we use a large Austrian data set, which consists of the direct price information collected by the statistical office and covers 80% of the CPI over eight years. We run cross-sectional tests, regressing the proportion of attractive prices and, separately, the excess proportion of price changes at the beginning of a year and at the beginning of a quarter, on various conditional frequencies of adjustment, inflation and its variability, dummies for good types, and other relevant variables. The results provide strong support for the model: the lower is, in a given market, the conditional frequency of price changes, the higher is the incidence of time- and state-regular adjustment.Optimal pricing; attractive prices; menu costs
Inhomogeneity effect in Wainwright-Marshman space-times
Green and Wald have presented a mathematically rigorous framework to study,
within general relativity, the effect of small scale inhomogeneities on the
global structure of space-time. The framework relies on the existence of a
one-parameter family of metrics that approaches the effective background metric
in a certain way. Although it is not necessary to know this family in an exact
form to predict properties of the backreaction effect, it would be instructive
to find explicit examples. In this paper, we provide the first example of such
a family of exact non-vacuum solutions to the Einstein's equations. It belongs
to the Wainwright-Marshman class and satisfies all of the assumptions of the
Green-Wald framework.Comment: 10 pages; revised version, as published in PR
Soft effective interactions between weakly charged polyelectrolyte chains
We apply extensive Molecular Dynamics simulations and analytical
considerations in order to study the conformations and the effective
interactions between weakly charged, flexible polyelectrolyte chains in
salt-free conditions. We focus on charging fractions lying below 20%, for which
case there is no Manning condensation of counterions and the latter can be thus
partitioned in two states: those that are trapped within the region of the
flexible chain and the ones that are free in the solution. We examine the
partition of counterions in these two states, the chain sizes and the monomer
distributions for various chain lengths, finding that the monomer density
follows a Gaussian shape. We calculate the effective interaction between the
centers of mass of two interacting chains, under the assumption that the chains
can be modeled as two overlapping Gaussian charge profiles. The analytical
calculations are compared with measurements from Molecular Dynamics
simulations. Good quantitative agreement is found for charging fractions below
10%, where the chains assume coil-like configurations, whereas deviations
develop for charge fraction of 20%, in which case a conformational transition
of the chain towards a rodlike configuration starts to take place.Comment: 38 pages, 12 figures, 2 tables. Revised version of the manuscript.
Selected for publication in the V\irtual Journal of Biological Physics
Research, issue of 1 september, 200
Fluid-fluid demixing transitions in colloid--polyelectrolyte star mixtures
We derive effective interaction potentials between hard, spherical colloidal
particles and star-branched polyelectrolytes of various functionalities and
smaller size than the colloids. The effective interactions are based on a
Derjaguin-like approximation, which is based on previously derived potentials
acting between polyelectrolyte stars and planar walls. On the basis of these
interactions we subsequently calculate the demixing binodals of the binary
colloid--polyelectrolyte star mixture, employing standard tools from
liquid-state theory. We find that the mixture is indeed unstable at moderately
high overall concentrations. The system becomes more unstable with respect to
demixing as the star functionality and the size ratio grow.Comment: 24 pages, 9 figures, submitted to Journal of Physics: Condensed
Matte
A broadband noise prediction scheme for low-noise centrifugal blowers
In this paper we outline a semi-empirical procedure for predicting the broadband sound power spectrum radiated by any member of a family of geometrically similar, centrifugal blowers. The prediction scheme is based on the use of a normalized sound power spectrum that is obtained by measuring the sound power radiated by one member of the blower family. In the present instance, a low noise blower design has been identified by conducting a large scale parametric study of blower noise as a function of geometrical design parameters and operating point; the resulting optimum design served to define the geometrical parameters of the blower family considered here. The prediction procedure allows calculation of either 1/3-octave band spectral levels or overall A-weighted levels. In addition it is possible to calculate noise surfaces, i.e., plots of A-weighted sound power level versus design parameters and operating condition; in this way it is easy to identify optimally quiet blower designs that satisfy specified pumping requirements. It has been found, for example, that large diameter impellers of relatively small width operating at low speeds tend to result in the lowest noise level at a given pumping requirement
Experimental design of a low noise centrifugal fan
The effect of various design parameters on broadband noise generation by centrifugal fans has been studied. The parameters varied included: blade type, radial and axial inlet clearance, scroll development angle, scroll development length and cutoff clearance. Scaling laws for pressure, flow and noise were applied to allow the A-weighted sound power levels of different fans to be compared at the same operating points. That approach has allowed an optimum low noise fan design to be identified. To extend the usefulness of that design, a semi-empirical procedure for predicting the broadband sound power spectrum of any member of a family of geometrically similar centrifugal fans has also been developed. The prediction procedure allows the calculation of 1/3-octave band sound power levels based on a measurement of the sound power radiated by a single member of the fan family. By the use of the prediction procedure, it is straightforward to identify optimally quiet fans that satisfy a range of pumping requirements
Directional approach to spatial structure of solutions to the Navier-Stokes equations in the plane
We investigate a steady flow of incompressible fluid in the plane. The motion
is governed by the Navier-Stokes equations with prescribed velocity
at infinity. The main result shows the existence of unique solutions for
arbitrary force, provided sufficient largeness of . Furthermore a
spacial structure of the solution is obtained in comparison with the Oseen
flow. A key element of our new approach is based on a setting which treats the
directino of the flow as \emph{time} direction. The analysis is done in
framework of the Fourier transform taken in one (perpendicular) direction and a
special choice of function spaces which take into account the inhomogeneous
character of the symbol of the Oseen system. From that point of view our
technique can be used as an effective tool in examining spatial asymptotics of
solutions to other systems modeled by elliptic equations
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