6,380 research outputs found
A pecking order of capital inflows and international tax principles
Even though financial markets today show a high degree of integration, the world capital market is still far from the textbook story of high capital mobility. The purpose of this paper is to highlight key sources of market failure in the context of international capital flows and to provide guidelines for efficient tax structure in the presence of capital market imperfections. The analysis distinguishes three types of international capital flows: foreign portfolio debt investment, foreign portfolio equity investment and foreign direct investment. The paper emphasizes the efficiency of a non-uniform tax treatment of the various vehicles of international capital flows. © 1998 Elsevier Science B.V.preprin
Cloning of Gaussian states by linear optics
We analyze in details a scheme for cloning of Gaussian states based on linear
optical components and homodyne detection recently demonstrated by U. L.
Andersen et al. [PRL 94 240503 (2005)]. The input-output fidelity is evaluated
for a generic (pure or mixed) Gaussian state taking into account the effect of
non-unit quantum efficiency and unbalanced mode-mixing. In addition, since in
most quantum information protocols the covariance matrix of the set of input
states is not perfectly known, we evaluate the average cloning fidelity for
classes of Gaussian states with the degree of squeezing and the number of
thermal photons being only partially known.Comment: 8 pages, 7 figure
Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses
Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources
Tuning the magnetic and structural phase transitions of PrFeAsO via Fe/Ru spin dilution
Neutron diffraction and muon spin relaxation measurements are used to obtain
a detailed phase diagram of Pr(Fe,Ru)AsO. The isoelectronic substitution of Ru
for Fe acts effectively as spin dilution, suppressing both the structural and
magnetic phase transitions. The temperature of the tetragonal-orthorhombic
structural phase transition decreases gradually as a function of x. Slightly
below the transition temperature coherent precessions of the muon spin are
observed corresponding to static magnetism, possibly reflecting a significant
magneto-elastic coupling in the FeAs layers. Short range order in both the Fe
and Pr moments persists for higher levels of x. The static magnetic moments
disappear at a concentration coincident with that expected for percolation of
the J1-J2 square lattice model
Measurement does not always aid state discrimination
We have investigated the problem of discriminating between nonorthogonal
quantum states with least probability of error. We have determined that the
best strategy for some sets of states is to make no measurement at all, and
simply to always assign the most commonly occurring state. Conditions which
describe such sets of states have been derived.Comment: 3 page
Minimum-error discrimination between symmetric mixed quantum states
We provide a solution of finding optimal measurement strategy for
distinguishing between symmetric mixed quantum states. It is assumed that the
matrix elements of at least one of the symmetric quantum states are all real
and nonnegative in the basis of the eigenstates of the symmetry operator.Comment: 10 page
Controlling thermal chaos in the mantle by positive feedback from radiative thermal conductivity
International audienceThe thermal conductivity of mantle materials has two components, the lattice component klat from phonons and the radiative component krad due to photons. These two contributions of variable thermal conductivity have a nonlinear dependence in the temperature, thus endowing the temperature equation in mantle convection with a strongly nonlinear character. The temperature derivatives of these two mechanisms have different signs, with ?klat /?T negative and dkrad /dT positive. This offers the possibility for the radiative conductivity to control the chaotic boundary layer instabilities developed in the deep mantle. We have parameterized the weight factor between krad and klat with a dimensionless parameter f , where f = 1 corresponds to the reference conductivity model. We have carried out two-dimensional, time-dependent calculations for variable thermal conductivity but constant viscosity in an aspect-ratio 6 box for surface Rayleigh numbers between 106 and 5 Ă— 106. The averaged PĂ©clet numbers of these flows lie between 200 and 2000. Along the boundary in f separating the chaotic and steady-state solutions, the number decreases and the Nusselt number increases with internal heating, illustrating the feedback between internal heating and radiative thermal conductivity. For purely basal heating situation, the time-dependent chaotic flows become stabilized for values of f of between 1.5 and 2. The bottom thermal boundary layer thickens and the surface heat flow increases with larger amounts of radiative conductivity. For magnitudes of internal heating characteristic of a chondritic mantle, much larger values of f , exceeding 10, are required to quench the bottom boundary layer instabilities. By isolating the individual conductive mechanisms, we have ascertained that the lattice conductivity is partly responsible for inducing boundary layer instabilities, while the radiative conductivity and purely depth-dependent conductivity exert a stabilizing influence and help to control thermal chaos developed in the deep mantle. These results have been verified to exist also in three-dimensional geometry and would argue for the need to consider the potentially important role played by radiative thermal conductivity in controlling chaotic flows in time-dependent mantle convection, the mantle heat transfer, the number of hotspots and the attendant mixing of geochemical anomalies
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