3,891 research outputs found
Optical phase-space reconstruction of mirror position at the attometer level
We describe an experiment in which the quadratures of the position of an
harmonically-bound mirror are observed at the attometer level. We have studied
the Brownian motion of the mirror, both in the free regime and in the
cold-damped regime when an external viscous force is applied by radiation
pressure. We have also studied the thermal-noise squeezing when the external
force is parametrically modulated. We have observed both the 50% theoretical
limit of squeezing at low gain and the parametric oscillation of the mirror for
a large gain.Comment: 10 pages, 11 figure
Beating quantum limits in optomechanical sensor by cavity detuning
We study the quantum limits in an optomechanical sensor based on a detuned
high-finesse cavity with a movable mirror. We show that the radiation pressure
exerted on the mirror by the light in the detuned cavity induces a modification
of the mirror dynamics and makes the mirror motion sensitive to the signal.
This leads to an amplification of the signal by the mirror dynamics, and to an
improvement of the sensor sensitivity beyond the standard quantum limit, up to
an ultimate quantum limit only related to the mechanical dissipation of the
mirror. This improvement is somewhat similar to the one predicted in detuned
signal-recycled gravitational-waves interferometers, and makes a high-finesse
cavity a model system to test these quantum effect
Dots to boxes: Do the size and shape of spatial units jeopardize economic geography estimations?
This paper evaluates, in the context of economic geography estimates, the magnitude of the distortions arising from the choice of zoning system, which is also known as the Modifiable Areal Unit Problem (MAUP). We consider three standard economic geography exercises (the analysis of spatial concentration, agglomeration economies, and trade determinants), using various French zoning systems differentiated according to the size and shape of spatial units, which are the two main determinants of the MAUP. While size matters a little, shape does so much less. Both dimensions seem to be of secondary importance compared to specification issues.MAUP ; concentration ;agglomeration ;wage equations ;gravity
DOTS TO BOXES: DO THE SIZE AND SHAPE OF SPATIAL UNITS JEOPARDIZE ECONOMIC GEOGRAPHY ESTIMATIONS?
This paper evaluates, in the context of economic geography estimates, the magnitude of the distortions arising from the choice of zoning system, which is also known as the Modifiable Areal Unit Problem (MAUP). We consider three standard economic geography exercises (the analysis of spatial concentration, agglomeration economies, and trade determinants), using various French zoning systems differentiated according to the size and shape of spatial units, which are the two main determinants of the MAUP. While size matters a little, shape does so much less. Both dimensions seem to be of secondary importance compared to specification issues.MAUP, concentration, agglomeration, wage equations, gravity
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