169 research outputs found
Emergency Farm Adjustments in the Wheat Area of South Dakota
SummaryThis circular tells briefly the story of some farmers in the Spring Wheat section of South Dakota. It shows the strenuous effort being made by these men to reduce expenses or to shift their production so that their income will equal their expenses.It illustrates certain adjustments that are being followed on some of the farms and suggests some changes that might be profitable on these and other farms.The most serious difficulty arises from the effort to pay the fixed charges-interest, taxes, and payments on indebtedness. On nearly all farms some adjustments are being made to obtain a farm income large enough to meet the immediately pressing expenses. These adjustments have taken the form of:1. Reducing cash expenses as much as is possible, sometimes to the extent that production is restricted or is carried on at greater risk. The effort to reduce expenses has in most cases led to a lower standard of living for the farm family.2. Reducing capital assets to meet payment demanded on indebtedness even though this means the abandonment of a practical long time system of farming.3. Family labor and the equipment is used to the limit of its capacity in an effort to increase the livestock enterprises and the acreage of crops so that the cash income can be increased.4. In some cases the acreage of cash grain has been increased at the expense of feed grains, legumes, or a cropping system that would be advantageous over the long period of time.5. In other cases, herd of stock cattle have been shifted to dairy production. In others, the practice of selling cattle as feeders has been changed to sale as finished or “warmed up cattle.”6. Farmers with low priced feed surplus have sometime found it necessary to shift from a conservative production program to the more speculative one of feeding livestock.7. In extreme cases, the operators have found it necessary to relinquish title to their farms and to continue operation as tenants to preserve their working capital and continue farming.8. Only farmers relatively free of debt can reduce operations and wait for an improvement of prices
Metastability in Interacting Nonlinear Stochastic Differential Equations II: Large-N Behaviour
We consider the dynamics of a periodic chain of N coupled overdamped
particles under the influence of noise, in the limit of large N. Each particle
is subjected to a bistable local potential, to a linear coupling with its
nearest neighbours, and to an independent source of white noise. For strong
coupling (of the order N^2), the system synchronises, in the sense that all
oscillators assume almost the same position in their respective local potential
most of the time. In a previous paper, we showed that the transition from
strong to weak coupling involves a sequence of symmetry-breaking bifurcations
of the system's stationary configurations, and analysed in particular the
behaviour for coupling intensities slightly below the synchronisation
threshold, for arbitrary N. Here we describe the behaviour for any positive
coupling intensity \gamma of order N^2, provided the particle number N is
sufficiently large (as a function of \gamma/N^2). In particular, we determine
the transition time between synchronised states, as well as the shape of the
"critical droplet", to leading order in 1/N. Our techniques involve the control
of the exact number of periodic orbits of a near-integrable twist map, allowing
us to give a detailed description of the system's potential landscape, in which
the metastable behaviour is encoded
The Continuum Directed Random Polymer
Motivated by discrete directed polymers in one space and one time dimension,
we construct a continuum directed random polymer that is modeled by a
continuous path interacting with a space-time white noise. The strength of the
interaction is determined by an inverse temperature parameter beta, and for a
given beta and realization of the noise the path evolves in a Markovian way.
The transition probabilities are determined by solutions to the one-dimensional
stochastic heat equation. We show that for all beta > 0 and for almost all
realizations of the white noise the path measure has the same Holder continuity
and quadratic variation properties as Brownian motion, but that it is actually
singular with respect to the standard Wiener measure on C([0,1]).Comment: 21 page
Ruelle-Perron-Frobenius spectrum for Anosov maps
We extend a number of results from one dimensional dynamics based on spectral
properties of the Ruelle-Perron-Frobenius transfer operator to Anosov
diffeomorphisms on compact manifolds. This allows to develop a direct operator
approach to study ergodic properties of these maps. In particular, we show that
it is possible to define Banach spaces on which the transfer operator is
quasicompact. (Information on the existence of an SRB measure, its smoothness
properties and statistical properties readily follow from such a result.) In
dimension we show that the transfer operator associated to smooth random
perturbations of the map is close, in a proper sense, to the unperturbed
transfer operator. This allows to obtain easily very strong spectral stability
results, which in turn imply spectral stability results for smooth
deterministic perturbations as well. Finally, we are able to implement an Ulam
type finite rank approximation scheme thus reducing the study of the spectral
properties of the transfer operator to a finite dimensional problem.Comment: 58 pages, LaTe
Coherent States Measurement Entropy
Coherent states (CS) quantum entropy can be split into two components. The
dynamical entropy is linked with the dynamical properties of a quantum system.
The measurement entropy, which tends to zero in the semiclassical limit,
describes the unpredictability induced by the process of a quantum approximate
measurement. We study the CS--measurement entropy for spin coherent states
defined on the sphere discussing different methods dealing with the time limit
. In particular we propose an effective technique of computing
the entropy by iterated function systems. The dependence of CS--measurement
entropy on the character of the partition of the phase space is analysed.Comment: revtex, 22 pages, 14 figures available upon request (e-mail:
[email protected]). Submitted to J.Phys.
Query Answering in Normal Logic Programs under Uncertainty
We present a simple, yet general top-down query answering procedure for normal logic programs over lattices and bilattices, where functions may appear in the rule bodies. Its interest relies on the fact that many approaches to paraconsistency and uncertainty in logic programs with or without non-monotonic negation are based on bilattices or lattices, respectively
Dissipation time and decay of correlations
We consider the effect of noise on the dynamics generated by
volume-preserving maps on a d-dimensional torus. The quantity we use to measure
the irreversibility of the dynamics is the dissipation time. We focus on the
asymptotic behaviour of this time in the limit of small noise. We derive
universal lower and upper bounds for the dissipation time in terms of various
properties of the map and its associated propagators: spectral properties,
local expansivity, and global mixing properties. We show that the dissipation
is slow for a general class of non-weakly-mixing maps; on the opposite, it is
fast for a large class of exponentially mixing systems which include uniformly
expanding maps and Anosov diffeomorphisms.Comment: 26 Pages, LaTex. Submitted to Nonlinearit
Large deviations for non-uniformly expanding maps
We obtain large deviation results for non-uniformly expanding maps with
non-flat singularities or criticalities and for partially hyperbolic
non-uniformly expanding attracting sets. That is, given a continuous function
we consider its space average with respect to a physical measure and compare
this with the time averages along orbits of the map, showing that the Lebesgue
measure of the set of points whose time averages stay away from the space
average decays to zero exponentially fast with the number of iterates involved.
As easy by-products we deduce escape rates from subsets of the basins of
physical measures for these types of maps. The rates of decay are naturally
related to the metric entropy and pressure function of the system with respect
to a family of equilibrium states. The corrections added to the published
version of this text appear in bold; see last section for a list of changesComment: 36 pages, 1 figure. After many PhD students and colleagues having
pointed several errors in the statements and proofs, this is a correction to
published article answering those comments. List of main changes in a new
last sectio
American Step-Up and Step-Down Default Swaps under Levy Models
This paper studies the valuation of a class of default swaps with the
embedded option to switch to a different premium and notional principal anytime
prior to a credit event. These are early exercisable contracts that give the
protection buyer or seller the right to step-up, step-down, or cancel the swap
position. The pricing problem is formulated under a structural credit risk
model based on Levy processes. This leads to the analytic and numerical studies
of several optimal stopping problems subject to early termination due to
default. In a general spectrally negative Levy model, we rigorously derive the
optimal exercise strategy. This allows for instant computation of the credit
spread under various specifications. Numerical examples are provided to examine
the impacts of default risk and contractual features on the credit spread and
exercise strategy.Comment: 35 pages, 5 figure
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