18,531 research outputs found
TRANSFORMATION OF FALLOW SYSTEMS UNDER POPULATION PRESSURE
In a fallow-cultivation model with biomass regeneration, we find the population-poverty-degradation linkage via the discount rate: slight increases in the discount rate result in increased cropping frequency and much lower soil fertility. Aggregating gives transitions equation declining in fertility and increasing in the fallow:cultivation ratio.Land Economics/Use,
FRW cosmology in Milgrom's bimetric theory of gravity
We consider spatially homogeneous and isotropic Friedmann-Robertson-Walker
(FRW) solutions of Milgrom's recently proposed class of bimetric theories of
gravity. These theories have two different regimes, corresponding to high and
low acceleration. We find simple power-law matter dominated solutions in both,
as well as solutions with spatial curvature, and exponentially expanding
solutions. In the high acceleration limit these solutions behave like the FRW
solutions of General Relativity, with a cosmological constant term that is of
the correct order of magnitude to explain the observed accelerating expansion
of the Universe. We find that solutions that remain in the high acceleration
regime for their entire history, however, require non-baryonic dark matter
fields, or extra interaction terms in their gravitational Lagrangian, in order
to be observationally viable. The low acceleration regime also provides some
scope to account for this deficit, with solutions that differ considerably from
their general relativistic counterparts.Comment: 12 page
Interest rate expectations and the slope of the money market yield curve
An examination of the relationship between yield and maturity in the money market. The expectations theory suggests that the yield curve should be a good predictor of future spot interest rates. A substantial body of research in recent years has tested this implication of the theory and discussed possible reasons for the lack of support for the theory from these tests. This paper provides a review of this literature.Interest rates
A sum-product theorem in function fields
Let be a finite subset of \ffield, the field of Laurent series in
over a finite field . We show that for any there
exists a constant dependent only on and such that
. In particular such a result is
obtained for the rational function field . Identical results
are also obtained for finite subsets of the -adic field for
any prime .Comment: Simplification of argument and note that methods also work for the
p-adic
On the involution fixity of exceptional groups of Lie type
The involution fixity of a permutation group of degree
is the maximum number of fixed points of an involution. In this paper we
study the involution fixity of primitive almost simple exceptional groups of
Lie type. We show that if is the socle of such a group, then either , or and is a Suzuki
group in its natural -transitive action of degree . This bound is
best possible and we present more detailed results for each family of
exceptional groups, which allows us to determine the groups with . This extends recent work of Liebeck and Shalev, who
established the bound for every almost simple
primitive group of degree with socle (with a prescribed list of
exceptions). Finally, by combining our results with the Lang-Weil estimates
from algebraic geometry, we determine bounds on a natural analogue of
involution fixity for primitive actions of exceptional algebraic groups over
algebraically closed fields.Comment: 45 pages; to appear in Int. J. Algebra Compu
Treasury bill versus private money market yield curves
An abstract for this article is not availableMoney market ; Treasury bills ; Interest rates
Bayesian fan charts for U.K. inflation: forecasting and sources of uncertainty in an evolving monetary system
We estimate a Bayesian vector autoregression for the U.K. with drifting coefficients and stochastic volatilities. We use it to characterize posterior densities for several objects that are useful for designing and evaluating monetary policy, including local approximations to the mean, persistence, and volatility of inflation. We present diverse sources of uncertainty that impinge on the posterior predictive density for inflation, including model uncertainty, policy drift, structural shifts and other shocks. We use a recently developed minimum entropy method to bring outside information to bear on inflation forecasts. We compare our predictive densities with the Bank of England's fan charts
The conquest of U.S. inflation: learning and robustness to model uncertainty
Previous studies have interpreted the rise and fall of U.S. inflation after World War II in terms of the Fed's changing views about the natural rate hypothesis but have left an important question unanswered. Why was the Fed so slow to implement the low-inflation policy recommended by a natural rate model even after economists had developed statistical evidence strongly in its favor? Our answer features model uncertainty. Each period a central bank sets the systematic part of the inflation rate in light of updated probabilities that it assigns to three competing models of the Phillips curve. Cautious behavior induced by model uncertainty can explain why the central bank presided over the inflation of the 1970s even after the data had convinced it to place much the highest probability on the natural rate model. JEL Classification: E31, E58, E65anticipated utility, Bayes' law, natural unemployment rate, Phillips curve, Robustness
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