1,587 research outputs found
No-arbitrage in discrete-time markets with proportional transaction costs and general information structure
We discuss the no-arbitrage conditions in a general framework for
discrete-time models of financial markets with proportional transaction costs
and general information structure. We extend the results of Kabanov and al.
(2002), Kabanov and al. (2003) and Schachermayer (2004) to the case where
bid-ask spreads are not known with certainty. In the "no-friction" case, we
retrieve the result of Kabanov and Stricker (2003)
Phase coexistence and resistivity near the ferromagnetic transition of manganites
Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and
their magnetic pair-breaking in the ferromagnetic phase [the so-called
current-carrier density collapse (CCDC)] has accounted for the first-order
ferromagnetic phase transition, colossal magnetoresistance (CMR), isotope
effect, and pseudogap in doped manganites. Here we propose an explanation of
the phase coexistence and describe the magnetization and resistivity of
manganites near the ferromagnetic transition in the framework of CCDC. The
present quantitative description of resistivity is obtained without any fitting
parameters by using the experimental resistivities far away from the transition
and the experimental magnetization, and essentially model independent.Comment: 10 pages, 3 figure
Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy
Using time-domain Terahertz spectroscopy we performed direct studies of the
photoinduced suppression and recovery of the superconducting gap in a
conventional BCS superconductor NbN. Both processes are found to be strongly
temperature and excitation density dependent. The analysis of the data with the
established phenomenological Rothwarf-Taylor model enabled us to determine the
bare quasiparticle recombination rate, the Cooper pair-breaking rate and the
electron-phonon coupling constant, \lambda = 1.1 +/- 0.1, which is in excellent
agreement with theoretical estimates.Comment: 4 pages, 4 figures; final version, accepted for publication in Phys.
Rev. Let
Optional Decomposition and Lagrange Multipliers
Let Q be the set of equivalent martingale measures for a given process S, and let X be a process which is a local supermartingale with respect to any measure in Q. The optional decomposition theorem for X states that there exists a predictable integrand ф such that the difference X−ф•S is a decreasing process. In this paper we give a new proof which uses techniques from stochastic calculus rather than functional analysis, and which removes any boundedness assumption
Hopping magneto-transport via nonzero orbital momentum states and organic magnetoresistance
In hopping magnetoresistance of doped insulators, an applied magnetic field
shrinks the electron (hole) s-wave function of a donor or an acceptor and this
reduces the overlap between hopping sites resulting in the positive
magnetoresistance quadratic in a weak magnetic field, B. We extend the theory
of hopping magnetoresistance to states with nonzero orbital momenta. Different
from s-states, a weak magnetic field expands the electron (hole) wave functions
with positive magnetic quantum numbers, m > 0, and shrinks the states with
negative m in a wide region outside the point defect. This together with a
magnetic-field dependence of injection/ionization rates results in a negative
weak-field magnetoresistance, which is linear in B when the orbital degeneracy
is lifted. The theory provides a possible explanation of a large low-field
magnetoresistance in disordered pi-conjugated organic materials (OMAR).Comment: 4 pages, 3 figure
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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