2,125 research outputs found
Exclusive vs Overlapping Viewers in Media Markets
This paper investigates competition for advertisers in media markets when
viewers can subscribe to multiple channels. A central feature of the model
is that channels are monopolists in selling advertising opportunities toward
their exclusive viewers, but they can only obtain a competitive price for
advertising opportunities to multi-homing viewers. Strategic incentives of
firms in this setting are different than those in former models of media
markets. If viewers can only watch one channel, then firms compete for
marginal consumers by reducing the amount of advertising on their channels.
In our model, channels have an incentive to increase levels of advertising,
in order to reduce the overlap in viewership. We take an account of the
differences between the predictions of the two types of models and find that
our model is more consistent with recent developments in broadcasting
markets. We also show that if channels can charge subscription fees on
viewers, then symmetric firms can end up in an asymmetric equilibrium in
which one collects all or most of its revenues from advertisers, while the
other channel collects most of its revenues via viewer fees
The impact of a natural time change on the convergence of the Crank-Nicolson scheme
We first analyse the effect of a square root transformation to the time
variable on the convergence of the Crank-Nicolson scheme when applied to the
solution of the heat equation with Dirac delta function initial conditions. In
the original variables, the scheme is known to diverge as the time step is
reduced with the ratio of the time step to space step held constant and the
value of this ratio controls how fast the divergence occurs. After introducing
the square root of time variable we prove that the numerical scheme for the
transformed partial differential equation now always converges and that the
ratio of the time step to space step controls the order of convergence,
quadratic convergence being achieved for this ratio below a critical value.
Numerical results indicate that the time change used with an appropriate value
of this ratio also results in quadratic convergence for the calculation of the
price, delta and gamma for standard European and American options without the
need for Rannacher start-up steps
A Penalty Method for the Numerical Solution of Hamilton-Jacobi-Bellman (HJB) Equations in Finance
We present a simple and easy to implement method for the numerical solution
of a rather general class of Hamilton-Jacobi-Bellman (HJB) equations. In many
cases, the considered problems have only a viscosity solution, to which,
fortunately, many intuitive (e.g. finite difference based) discretisations can
be shown to converge. However, especially when using fully implicit time
stepping schemes with their desirable stability properties, one is still faced
with the considerable task of solving the resulting nonlinear discrete system.
In this paper, we introduce a penalty method which approximates the nonlinear
discrete system to first order in the penalty parameter, and we show that an
iterative scheme can be used to solve the penalised discrete problem in
finitely many steps. We include a number of examples from mathematical finance
for which the described approach yields a rigorous numerical scheme and present
numerical results.Comment: 18 Pages, 4 Figures. This updated version has a slightly more
detailed introduction. In the current form, the paper will appear in SIAM
Journal on Numerical Analysi
Epitaxy of Fe3O4 on Si(001) by pulsed laser deposition using a TiN/MgO buffer layer
Epitaxy of oxide materials on silicon (Si) substrates is of great interest
for future functional devices using the large variety of physical properties of
the oxides as ferroelectricity, ferromagnetism, or superconductivity. Recently,
materials with high spin polarization of the charge carriers have become
interesting for semiconductor-oxide hybrid devices in spin electronics. Here,
we report on pulsed laser deposition of magnetite (Fe3O4) on Si(001) substrates
cleaned by an in situ laser beam high temperature treatment. After depositing a
double buffer layer of titanium nitride (TiN) and magnesium oxide (MgO), a high
quality epitaxial magnetite layer can be grown as verified by RHEED intensity
oscillations and high resolution x-ray diffraction.Comment: submitte
Sub-unit cell layer-by-layer growth of Fe3O4, MgO, and Sr2RuO4 thin films
The use of oxide materials in oxide electronics requires their controlled
epitaxial growth. Recently, it was shown that Reflection High Energy Electron
Diffraction (RHEED) allows to monitor the growth of oxide thin films even at
high oxygen pressure. Here, we report the sub-unit cell molecular or block
layer growth of the oxide materials Sr2RuO4, MgO, and magnetite using Pulsed
Laser Deposition (PLD) from stoichiometric targets. Whereas for perovskites
such as SrTiO3 or doped LaMnO3 a single RHEED intensity oscillation is found to
correspond to the growth of a single unit cell, in materials where the unit
cell is composed of several molecular layers or blocks with identical
stoichiometry, a sub-unit cell molecular or block layer growth is established
resulting in several RHEED intensity oscillations during the growth of a single
unit-cell
Lil3 assembles as chlorophyll-binding protein complex during deetiolation
AbstractDark-grown angiosperm seedlings are etiolated and devoid of chlorophyll. Deetiolation is triggered by light leading to chlorophyll dependent accumulation of the photosynthetic machinery. The transfer of chlorophyll to the chlorophyll-binding proteins is still unclear. We demonstrate here that upon illumination of dark-grown barley seedlings, two new pigment-binding protein complexes are de novo accumulated. Pigments bound to both complexes are identified as chlorophyll a and protochlorophyll a. By auto-fluorescence tracking and mass spectrometry, we show that exclusively Lil3 is the pigment-binding complex subunit in both complexes
The proteome of the heterocyst cell wall in Anabaena sp. PCC 7120
Anabaena sp. PCC 7120 is a filamentous cyanobacterium that serves as a model to analyze prokaryotic cell differentiation, evolutionary development of plastids, and the regulation of nitrogen fixation. The cell wall is the cellular structure in contact with the surrounding medium. To understand the dynamics of the cell wall proteome during cell differentiation, the cell wall from Anabaena heterocysts was enriched and analyzed. In line with the recently proposed continuity of the outer membrane along the Anabaena filament, most of the proteins identified in the heterocyst cell-wall fraction are also present in the cell wall of vegetative cells, even though the lipid content of both membranes is different
Penalty Methods for the Solution of Discrete HJB Equations -- Continuous Control and Obstacle Problems
In this paper, we present a novel penalty approach for the numerical solution
of continuously controlled HJB equations and HJB obstacle problems. Our results
include estimates of the penalisation error for a class of penalty terms, and
we show that variations of Newton's method can be used to obtain globally
convergent iterative solvers for the penalised equations. Furthermore, we
discuss under what conditions local quadratic convergence of the iterative
solvers can be expected. We include numerical results demonstrating the
competitiveness of our methods.Comment: 31 Pages, 7 Figure
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