1,579 research outputs found
Einleitung: Subjekthaftigkeit, Digitalität, Fiktion und Alltagswirklichkeit
Welche Ansätze und welche Perspektiven finden sich in der gegenwärtigen Forschung zum Subjekt und den daran gekoppelten Praktiken, Formen, Kulturen und Ordnungen? Welche Aspekte des Digitalen gilt es in dieser Hinsicht präzise zu bestimmen und wie genau passen die Kategorien des Subjekts und des Digitalen zusammen? Die Einleitung wirft einen Blick auf wesentliche Positionen der gegenwärtigen Subjektforschung, fragt nach dem Beitrag, den die Literaturwissenschaft dabei erbringen kann und stellt knapp die Aufsätze dieses Sammelbandes vor
Theory of ground state cooling of a mechanical oscillator using dynamical back-action
A quantum theory of cooling of a mechanical oscillator by radiation
pressure-induced dynamical back-action is developed, which is analogous to
sideband cooling of trapped ions. We find that final occupancies well below
unity can be attained when the mechanical oscillation frequency is larger than
the cavity linewidth. It is shown that the final average occupancy can be
retrieved directly from the optical output spectrum.Comment: 5 pages, 2 figure
Initial-state dependence of coupled electronic and nuclear fluxes in molecules
We demonstrate that coupled electronic and nuclear fluxes in molecules can strongly depend on the initial state
preparation. Starting the dynamics of an aligned D2
+ molecule at two different initial conditions, the inner and the outer turning points, we observe qualitatively different oscillation patterns of the nuclear fluxes developing after 30 fs. This corresponds to different orders of magnitude bridged by the time evolution of the nuclear dispersion. Moreover, there are attosecond time intervals within which the electronic fluxes do not adapt to the nuclei motion depending on the initial state. These results are inferred from two different approaches for the numerical flux simulation, which are both in good agreement
Separation quality of a geometric ratchet
We consider an experimentally relevant model of a geometric ratchet in which
particles undergo drift and diffusive motion in a two-dimensional periodic
array of obstacles, and which is used for the continuous separation of
particles subject to different forces. The macroscopic drift velocity and
diffusion tensor are calculated by a Monte-Carlo simulation and by a
master-equation approach, using the correponding microscopic quantities and the
shape of the obstacles as input. We define a measure of separation quality and
investigate its dependence on the applied force and the shape of the obstacles
Regulatory Impact Assessment: A survey of selected developing and emerging economies
Regulatory impact assessment (RIA) involves a systematic appraisal of the
social, economic and environmental impacts of proposed regulations and other
kinds of policy instruments before they are adopted. A vast amount of academic
literature in the last decade has charted the diffusion of RIA in OECD
countries and EU member states. However, relatively little is known about the
extent to which RIA has been adopted and implemented in developing countries.
The last research attempting to shed light on this issue over a decade ago
found that a number of were beginning to apply some form of regulatory
assessment but that its development was at an early stage. Since then RIA has
become almost universally adopted in OECD and EU member states as well as
promoted as a tool for good (regulatory) governance in developing countries by
international donors and organizations such as OECD, the International Finance
Corporation of the World Bank Group (IFC). What, then, is the extent of RIA
adoption and implementation in these countries today? This working paper
addresses this question through a survey of RIA in 14 developing and emerging
economies based on documentary analysis as well as semi-structured interviews
with key stakeholders. The survey explores topics such as the legal and
institutional framework of RIA, organizational capacity, and use of tools and
methods (e.g. Cost Benefit Analysis). The results suggest that while an
increasing number of developing countries have made efforts to introduce RIA
in their decision making processes, these efforts have not yet led to a
sustainable RIA system which significantly contributes to the good regulatory
governance of these countries
The information about the state of a qubit gained by a weakly coupled detector
We analyze the information that one can learn about the state of a quantum
two-level system, i.e. a qubit, when probed weakly by a nearby detector. In
particular, we focus on the case when the qubit Hamiltonian and the qubit's
operator being probed by the detector do not commute. Because the qubit's state
keeps evolving while being probed and because the measurement data is mixed
with a detector-related background noise, one might expect the detector to fail
in this case. We show, however, that under suitable conditions and by proper
analysis of the measurement data useful information about the state of the
qubit can be extracted. It turns out that the measurement basis is
stochastically determined every time the experiment is repeated. We analyze in
detail the probability distributions that govern the choice of measurement
bases. We also analyze the information acquisition rate and show that it is
largely unaffected by the apparent conflict between the measurement and
intrinsic qubit dynamics. We discuss the relation between our analysis and the
stochastic master equation that describes the evolution of the qubit's state
under the influence of measurement and decoherence. In particular, we write
down a stochastic equation that encompasses the usual stochastic master
equation for the evolution of the qubit's density matrix and additionally
contains the measurement information that can be extracted from the observed
signal.Comment: 21 pages (two column), 8 figure
Current-voltage correlations in interferometers
We investigate correlations of current at contacts and voltage fluctuations
at voltage probes coupled to interferometers. The results are compared with
correlations of current and occupation number fluctuations at dephasing probes.
We use a quantum Langevin approach for the average quantities and their
fluctuations. For higher order correlations we develop a stochastic path
integral approach and find the generating functions of voltage or occupation
number fluctuations. We also derive a generating function for the joint
distribution of voltage or occupation number at the probe and current
fluctuations at a terminal of a conductor. For energy independent scattering we
found earlier that the generating function of current cumulants in
interferometers with a one-channel dephasing or voltage probe are identical.
Nevertheless, the distribution function for voltage and the distribution
function for occupation number fluctuations differ, the latter being broader
than that of former in all examples considered here.Comment: 23 pages, 10 figures, minor changes, additional appendix, added
reference
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