14,897 research outputs found
Sensitivity below the standard quantum limit in gravitational wave detectors with Michelson-Fabry-Perot readout
We calculate the quantum noise limited displacement sensitivity of a
Michelson-Fabry-Perot (MFP) with detuned cavities, followed by phase-sensitive
homodyne detection. We show that the standard quantum limit can be surpassed
even with resonant cavities and without any signal-recycling mirror nor
additional cavities. Indeed, thanks to the homodyne detection, the output field
quadrature can be chosen in such a way to cancel the effect of input amplitude
fluctuations, i.e., eliminating the force noise. With detuned cavities, the
modified opto-mechanical susceptivity allows to reach unlimited sensitivity for
large enough (yet finite) optical power. Our expressions include mirror losses
and cavity delay effect, for a realistic comparison with experiments. Our study
is particularly devoted to gravitational wave detectors and we consider both an
interferometer with free-falling mirrors, and a MFP as readout for a massive
detector. In the latter case, the sensitivity curve of the recently conceived
'DUAL' detector, based on two acoustic modes, is obtained
Power in the Multinational Corporation in Industry Equilibrium
Recent theories of the multinational corporation introduce the property rights model of the firm and examine whether to integrate our outsource firm activities locally or to a foreign country. This paper focus instead on the internal organization of the multinational corporation by examining the power allocation between headquarters and subsidiaries. We provide a framework to analyse the interaction between the decision to serve the local market by exporting or FDI, market acces and the optimal mode of organization of the multinational corporation. We find that subsidiary managers are given most autonomy in their decision how to run the firm at intermediate levels of local competition. We then provide comparative statics for changes in fixed FDI entry costs and trade costs, information technology, the number of local competitors, and in the size of the local market
Tilted excitation implies odd periodic resonances
This work was supported by the Brazilian agencies FAPESP and CNPq. MSB also acknowledges the Engineering and Physical Sciences Research Council grant Ref. EP/I032606/1. GID thanks Felipe A. C. Pereira for fruitful discussions.Peer reviewedPostprin
Corporate Hierarchies and the Size of Nations: Theory and Evidence
Corporate organization varies within a country and across countries with country size. The paper starts by establishing some facts about corporate organization based on unique data of 660 Austrian and German corporations. The larger country (Germany) has larger firms with flatter more decentral corporate hierarchies compared to the smaller country (Austria). Firms in the larger country change their organization less fast than firms in the smaller country. Over time firms have been introducing less hierarchical organizations by delegating power to lower levels of the corporation. We develop a theory which explains these facts and which links these features to the trade environment that countries and firms face. We introduce firms with internal hierarchies in a Krugman (1980) model of trade. We show that international trade and the toughness of competition in international markets induce a power struggle in firms which eventually leads to decentralized corporate hierarchies. We offer econometric evidence which is consistent with the models predictions
Degenerate four-wave mixing in triply-resonant Kerr cavities
We demonstrate theoretical conditions for highly-efficient degenerate
four-wave mixing in triply-resonant nonlinear (Kerr) cavities. We employ a
general and accurate temporal coupled-mode analysis in which the interaction of
light in arbitrary microcavities is expressed in terms a set of coupling
coefficients that we rigorously derive from the full Maxwell equations. Using
the coupled-mode theory, we show that light consisting of an input signal of
frequency can, in the presence of pump light at
, be converted with quantum-limited efficiency into an output shifted
signal of frequency , and we derive expressions for
the critical input powers at which this occurs. We find that critical powers in
the order of 10mW assuming very conservative cavity parameters (modal volumes
cubic wavelengths and quality factors . The standard
Manley-Rowe efficiency limits are obtained from the solution of the classical
coupled-mode equations, although we also derive them from simple
photon-counting "quantum" arguments. Finally, using a linear stability
analysis, we demonstrate that maximal conversion efficiency can be retained
even in the presence of self- and cross-phase modulation effects that generally
act to disrupt the resonance condition.Comment: 13 pages, 8 figures. To appear in Physical Review
Interplay between the magnetic anisotropy contributions of Cobalt nanowires
We report on the magnetic properties and the crystallographic structure of
the cobalt nanowire arrays as a function of their nanoscale dimensions. X-ray
diffraction measurements show the appearance of an in-plane HCP-Co phase for
nanowires with 50 nm diameter, suggesting a partial reorientation of the
magnetocrystalline anisotropy axis along the membrane plane with increasing
pore diameter. No significant changes in the magnetic behavior of the nanowire
system are observed with decreasing temperature, indicating that the effective
magnetoelastic anisotropy does not play a dominant role in the remagnetization
processes of individual nanowires. An enhancement of the total magnetic
anisotropy is found at room temperature with a decreasing nanowire
diameter-to-length ratio (d/L), a result that is quantitatively analyzed on the
basis of a simplified shape anisotropy model.Comment: 8 pages, 4 figure
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