1,585 research outputs found
No arbitrage and closure results for trading cones with transaction costs
In this paper, we consider trading with proportional transaction costs as in Schachermayer’s paper (Schachermayer in Math. Finance 14:19–48, 2004). We give a necessary and sufficient condition for , the cone of claims attainable from zero endowment, to be closed. Then we show how to define a revised set of trading prices in such a way that, firstly, the corresponding cone of claims attainable for zero endowment, , does obey the fundamental theorem of asset pricing and, secondly, if is arbitrage-free then it is the closure of . We then conclude by showing how to represent claims
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Myosin II-Mediated Focal Adhesion Maturation Is Tension Insensitive
Myosin II motors drive changes in focal adhesion morphology and composition in a “maturation process” that is crucial for regulating adhesion dynamics and signaling guiding cell adhesion, migration and fate. The underlying mechanisms of maturation, however, have been obscured by the intermingled effects of myosin II on lamellar actin architecture, dynamics and force transmission. Here, we show that focal adhesion growth rate stays constant even when cellular tension is reduced by 75%. Focal adhesion growth halts only when myosin stresses are sufficiently low to impair actin retrograde flow. Focal adhesion lifetime is reduced at low levels of cellular tension, but adhesion stability can be rescued at low levels of force by over-expression of α-actinin or constitutively active Dia1. Our work identifies a minimal myosin activity threshold that is necessary to drive lamellar actin retrograde flow is sufficient to permit focal adhesion elongation. Above this nominal threshold, myosin-mediated actin organization and dynamics regulate focal adhesion growth and stability in a force-insensitive fashion.</p
The Illusion of Being Located in Dynamic Virtual Environments. Can Eye Movement Parameters Predict Spatial Presence?
Attention allocation towards the mediated environment is assumed to be a necessary precondition to feel localized in a virtual world. In presence research, however, the potential of eye movement research has not been fully exploited so far. In this study, participants (N=44) rode on a virtual roller coaster simulation. We compare participants scoring high versus low on presence. During the ride, the eye movements and subjective ex post presence judgments were assessed. We found high sensations of presence to be associated with fewer fixations and a tendency towards longer fixation durations. In contrast to the immersive tendency trait, eye movement parameters can predict presence
Princípio pagador-poluidor - como princípio norteador da cobrana pelo uso dos recursos hídricos
O presente trabalho objetiva conduzir uma análise detalhada do princípio poluidor-pagador,amplamente consagrado em diversos ordenamentos legais, com o intuito de aclarar sua interpretação de modo que possa ser aplicado uniformemente e,por conseguinte,mais freqüentemente. Este estudo enfoca a análise da doutrina,bem como de alguns artigos,visando ao exame dos aspectos econômicos e jurídicos do PPP,à investigação da relação entre o PPP e outros princípios ambientais,em especial, a responsabilidade civil pó danos ambientais e o chamado "princípio do usuário-pagador", de sua evolução,terminologia e finalidades ,sem deixar de mencionar a importância da adoção de instrumentos econômicos(mormente a cobrança pelo uso da água) para a proteção qualitativa e quantitativa dos recursos hídricos,a guiar a implementação efetiva do princípio em tela
Comparison of K-doped and pure cold-rolled tungsten sheets: As-rolled condition and recrystallization behaviour after isochronal annealing at different temperatures
Severely deformed cold-rolled tungsten is a promising structural material for future fusion reactor applications due to high melting temperature and excellent mechanical properties. However, the fine-grained microstructure after deformation is not stable at temperatures above 800 °C, leading to brittle material behaviour.
In this study, we utilize potassium-doping to inhibit recrystallization of tungsten sheets, a mechanism well known from incandescent lamp wires. We produced K-doped tungsten sheets by warm-rolling and subsequent cold-rolling with five different logarithmic strains up to 4.6, and equivalently rolled pure tungsten sheets. Both sets of materials are compared using EBSD and microhardness testing.
In both materials, the hardness increases and the grain size along normal direction decreases with strain; the densities of low and high angle boundaries increase in particular during cold-rolling. The K-doped W sheet reaches the highest hardness with 772 ± 8 HV0.1, compared to the pure W sheet with 711 ± 14 HV0.1. All boundaries taken into account, a Hall-Petch relation describes the hardness evolution nicely, except a deviation of the K-doped tungsten sheet rolled to highest strain with its much higher hardness.
The similar structural and mechanical properties of both materials in the as-rolled condition allow further studies of recrystallization behaviour of the new K-doped material with a benchmark against the equivalent pure tungsten sheets. Isochronal annealing for 1 h was performed at different temperatures between 700 °C and 2200 °C. A sharp decrease in hardness to intermediate values is observed at around 900 °C for both materials, presumably reflecting extended recovery. A second decrease is observed at 1400 °C for pure tungsten, approaching the hardness of a single crystal and indicating recrystallization and severe growth of grains. For K-doped tungsten, however, the occurrence of the second decrease is shifted to higher temperatures from 1400 °C to 1800 °C with increasing strain and an intermediate hardness is maintained up to 1800 °C. We refer this dependence of the recrystallization resistance on strain in the K-doped material to the dispersion of K-bubbles, resulting in increased Zener pinning forces retarding boundary motion
Gauge Independence of IR singularities in Non-Commutative QFT - and Interpolating Gauges
IR divergences of a non-commutative U(1) Maxwell theory are discussed at the
one-loop level using an interpolating gauge to show that quadratic IR
divergences are independent not only from a covariant gauge fixing but also
independent from an axial gauge fixing.Comment: 11 pages, 2 figures, v1 minor correction
Pion-nucleus optical potential valid up to the DELTA-resonance region
We present in this article an optical potential for the -nucleus
interaction that can be used in various studies involving -nucleus
channels. Based on earlier treatments of the low energy -nucleus optical
potential, we have derived a potential expression applicable from threshold up
to the -resonance region. We extracted the impulse approximation form
for this potential from the scattering amplitude and then added to it
kinematical and physical corrections. The kinematic corrections arise from
transforming the impulse approximation expression from the center of
mass frame to the -nucleus center of mass frame, while the physical
corrections arise mostly from the many-body nature of the -nucleus
interaction. By taking advantage of the experimental progress in our knowledge
of the process, we have updated earlier treatments with parameters
calculated from state-of-the-art experimental measurements.Comment: 23 pages, 12 figures. Accepted for publication in Physical Review
Lessons to be learned from the coherent photoproduction of pseudoscalar mesons
We study the coherent photoproduction of pseudoscalar mesons---particularly
of neutral pions---placing special emphasis on the various sources that put
into question earlier nonrelativistic-impulse-approximation calculations. These
include: final-state interactions, relativistic effects, off-shell ambiguities,
and violations to the impulse approximation. We establish that, while
distortions play an essential role in the modification of the coherent cross
section, the uncertainty in our results due to the various choices of
optical-potential models is relatively small (of at most 30%). By far the
largest uncertainty emerges from the ambiguity in extending the many
on-shell-equivalent representations of the elementary amplitude off the mass
shell. Indeed, relativistic impulse-approximation calculations that include the
same pionic distortions, the same nuclear-structure model, and two sets of
elementary amplitudes that are identical on-shell, lead to variations in the
magnitude of the coherent cross section by up to factors of five. Finally, we
address qualitatively the assumption of locality implicit in most
impulse-approximation treatments, and suggest that the coherent reaction
probes---in addition to the nuclear density---the polarization structure of the
nucleus.Comment: Manuscript is 27 pages long and includes 11 eps figure
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