8,823 research outputs found
Power and Inefficient Institutions
This paper is concerned with the persistence of inefficient institutions. Why are they not replaced by more effcient ones? What and/or who prevents such change? We provide an answer to these questions based on two key ideas. The principal idea is that institutional change on an issue may adversely affect the bargaining power of some agents on different issues. The second is that certain kinds of frictions (or transaction costs) are present, which do not allow for this deteriorating bargaining power to be compensated for. A key insight obtained from our analysis is that, the greater is the degree of inequality in the playersďż˝ bargaining powers the more likely it is that ineffcient institutions will persist.
Quantum Mechanics as a Framework for Dealing with Uncertainty
Quantum uncertainty is described here in two guises: indeterminacy with its
concomitant indeterminism of measurement outcomes, and fuzziness, or
unsharpness. Both features were long seen as obstructions of experimental
possibilities that were available in the realm of classical physics. The birth
of quantum information science was due to the realization that such
obstructions can be turned into powerful resources. Here we review how the
utilization of quantum fuzziness makes room for a notion of approximate joint
measurement of noncommuting observables. We also show how from a classical
perspective quantum uncertainty is due to a limitation of measurability
reflected in a fuzzy event structure -- all quantum events are fundamentally
unsharp.Comment: Plenary Lecture, Central European Workshop on Quantum Optics, Turku
2009
Time Scales for Viscous Flow, Atomic Transport, and Crystallization in the Liquid and Supercooled Liquid States of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5
The shear viscosity of liquid Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 has been measured. At the liquidus temperature we find an extremely high viscosity of 2.5 Pa s, favoring glass formation. At deep supercooling the time scales for the diffusion of small and medium sized atoms as reported in the literature decouple from the internal relaxation time as probed by our viscosity measurements. Similarly, crystallization from the supercooled liquid state can be described with an effective diffusivity that scales with the viscosity at high temperatures and is Arrhenius-like at deep supercooling
Decomposition and primary crystallization in undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 melts
Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glasses were prepared by cooling the melt with a rate of about 10 K/s and investigated with respect to their chemical and structural homogeneity by atom probe field ion microscopy and transmission electron microscopy. The measurements on these slowly cooled samples reveal that the alloy exhibits phase separation in the undercooled liquid state. Significant composition fluctuations are found in the Be and Zr concentration but not in the Ti, Cu, and Ni concentration. The decomposed microstructure is compared with the microstructure obtained upon primary crystallization, suggesting that the nucleation during primary crystallization of this bulk glass former is triggered by the preceding diffusion controlled decomposition in the undercooled liquid state
Preserving the measure of compatibility between quantum states
In this paper after defining the abstract concept of compatibility-like
functions on quantum states, we prove that every bijective transformation on
the set of all states which preserves such a function is implemented by an
either unitary or antiunitary operator.Comment: 11 pages, submitted for publicatio
Processing of carbon-fiber-reinforced Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass composites
Carbon-fiber-reinforced bulk metallic glass composites are produced by infiltrating liquid Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 into carbon fiber bundles with diameter of the individual fiber of 5 mum. Reactive wetting occurs by the formation of a ZrC layer around the fibers. This results in a composite with a homogeneous fiber distribution. The volume fraction of the fibers is about 50% and the density of the composite amounts to 4.0 g/cm(^3)
Structural change of vortex patterns in anisotropic Bose-Einstein condensates
We study the changes in the spatial distribution of vortices in a rotating
Bose-Einstein condensate due to an increasing anisotropy of the trapping
potential. Once the rotational symmetry is broken, we find that the vortex
system undergoes a rich variety of structural changes, including the formation
of zig-zag and linear configurations. These spatial re-arrangements are well
signaled by the change in the behavior of the vortex-pattern eigenmodes against
the anisotropy parameter. The existence of such structural changes opens up
possibilities for the coherent exploitation of effective many-body systems
based on vortex patterns.Comment: 5 pages, 4 figure
Experimental determination of a time–temperature-transformation diagram of the undercooled Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy using the containerless electrostatic levitation processing technique
High temperature high vacuum electrostatic levitation was used to determine the complete time–temperature–transformation (TTT) diagram of the Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass forming alloy in the undercooled liquid state. This is the first report of experimental data on the crystallization kinetics of a metallic system covering the entire temperature range of the undercooled melt down to the glass transition temperature. The measured TTT diagram exhibits the expected "C" shape. Existing models that assume polymorphic crystallization cannot satisfactorily explain the experimentally obtained TTT diagram. This originates from the complex crystallization mechanisms that occur in this bulk glass-forming system, involving large composition fluctuations prior to crystallization as well as phase separation in the undercooled liquid state below 800 K
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