1,609 research outputs found
Limits to Linear Price Behaviour: Target Zones for Futures Prices Regulated By Limits
This paper analyzes the random walk behaviour of futures prices when the exchange regulated by price limits. Using a model analogous to exchange rate target zone models, the study tests for the existence of a nonlinear S-shape relation between observed and theoretical futures prices. This phenomenon reflects the adjustment in traders' expectations even when limits are not actually hit. The approach is illustrated for five agricultural futures contracts traded at the Chicago Board of Trade. There is some evidence of nonlinearity in quiet periods. In cases of fundamental realignments, that is volatile periods, this non-liearity disappears.price limits; target zones; gravitation; mean reversion
Rapid roll Inflation with Conformal Coupling
Usual inflation is realized with a slow rolling scalar field minimally
coupled to gravity. In contrast, we consider dynamics of a scalar with a flat
effective potential, conformally coupled to gravity. Surprisingly, it contains
an attractor inflationary solution with the rapidly rolling inflaton field. We
discuss models with the conformal inflaton with a flat potential (including
hybrid inflation). There is no generation of cosmological fluctuations from the
conformally coupled inflaton. We consider realizations of modulated
(inhomogeneous reheating) or curvaton cosmological fluctuations in these
models. We also implement these unusual features for the popular
string-theoretic warped inflationary scenario, based on the interacting D3-anti
D3 branes. The original warped brane inflation suffers a large inflaton mass
due to conformal coupling to 4-dimensional gravity. Instead of considering this
as a problem and trying to cure it with extra engineering, we show that warped
inflation with the conformally coupled, rapidly rolling inflaton is yet
possible with N=37 efoldings, which requires low energy scales 1-100 TeV of
inflation. Coincidentally, the same warping numerology can be responsible for
the hierarchy. It is shown that the scalars associated with angular isometries
of the warped geometry of compact manifold (e.g. S^3 of KS geometry) have
solutions identical to conformally coupled modes and also cannot be responsible
for cosmological fluctuations. We discuss other possibilities.Comment: 15 pages, version accepted for publication in PR
Migration of Price Discovery With Constrained Futures Markets
This paper investigates the information content of futures option prices when the futures price is regulated while the futures option price itself is not. The New York Board of Trade provides the empirical setting for this type of dichotomy in regulation. Most commodity derivatives markets regulate prices of all derivatives on a particular commodity simultaneously. NYBOT has taken an almost unique position by imposing daily price limits on their futures contracts while leaving the options prices on these futures contracts unconstrained. The study takes a particular interest in the volatility and futures prices of the options-implied risk neutral density when the underlying futures contract is locked limit.option implied density; price limits
Reheating and thermalization in a simple scalar model
We consider a simple model for the Universe reheating, which consists of a
single self--interacting scalar field in Minkowskian space--time. Making use of
the existence of an additional small parameter proportional to the amplitude of
the initial spatially homogeneous field oscillations, we show that the behavior
of the field can be found reliably. We describe the evolution of the system
from the homogeneous oscillations to the moment when thermalization is
completed. We compare our results with the Hartree--Fock approximation and
argue that some properties found for this model may be the common features of
realistic theories.Comment: Some changes in Introduction and Discussion, comparison with the
Hartree--Fock results added. 37 pages, 2 postscript figures attache
Topological Defects Formation after Inflation on Lattice Simulation
We consider the formation of topological defects after inflation. In order to
take into account the effects of the rescattering of fluctuations, we integrate
the classical equation that describes the evolution of a complex scalar field
on the two-dimensional lattice with a slab symmetry. The growth of fluctuations
during preheating is found not to be enough for defect formation, and rather a
long stage of the rescattering of fluctuations after preheating is necessary.
We conclude that the topological defects are not formed if the breaking scale
\eta is lager than \sim (2 - 3)\times 10^{16} GeV.Comment: 7 pages, RevTex, 10 postscript figures included; version to be
published in Phys. Rev.
The Development of Equilibrium After Preheating
We present a fully nonlinear study of the development of equilibrium after
preheating. Preheating is the exponentially rapid transfer of energy from the
nearly homogeneous inflaton field to fluctuations of other fields and/or the
inflaton itself. This rapid transfer leaves these fields in a highly nonthermal
state with energy concentrated in infrared modes. We have performed lattice
simulations of the evolution of interacting scalar fields during and after
preheating for a variety of inflationary models. We have formulated a set of
generic rules that govern the thermalization process in all of these models.
Notably, we see that once one of the fields is amplified through parametric
resonance or other mechanisms it rapidly excites other coupled fields to
exponentially large occupation numbers. These fields quickly acquire nearly
thermal spectra in the infrared, which gradually propagates into higher
momenta. Prior to the formation of total equilibrium, the excited fields group
into subsets with almost identical characteristics (e.g. group effective
temperature). The way fields form into these groups and the properties of the
groups depend on the couplings between them. We also studied the onset of chaos
after preheating by calculating the Lyapunov exponent of the scalar fields.Comment: 15 pages, 23 figure
On generation of metric perturbations during preheating
We consider the generation of the scalar mode of the metric perturbations
during preheating stage in a two field model with the potential . We discuss two possible
sources of such perturbations: a) due to the coupling between the perturbation
of the matter field and the background part of the matter field
, b) due to non-linear fluctuations in a condensate of
``particles'' of the field . Both types of the metric perturbations are
assumed to be small, and estimated using the linear theory of the metric
perturbations. We estimate analytically the upper limit of the amplitude of the
metric perturbations for all scales in the limit of so-called broad resonance,
and show that the large scale metric perturbations are very small, and taking
them into account does not influence the standard picture of the production of
the metric perturbations in inflationary scenario.Comment: This version is to be published in PRD, new references added and
typos correcte
Superluminal Optical Phase Conjugation: Pulse Reshaping and Instability
We theoretically investigate the response of optical phase conjugators to
incident probe pulses. In the stable (sub-threshold) operating regime of an
optical phase conjugator it is possible to transmit probe pulses with a
superluminally advanced peak, whereas conjugate reflection is always
subluminal. In the unstable (above-threshold) regime, superluminal response
occurs both in reflection and in transmission, at times preceding the onset of
exponential growth due to the instability.Comment: 9 pages, 6 figures, RevTex, to appear in Phys. Rev.
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