3,842 research outputs found
Dynamical Casimir effect in curved spacetime
A boundary undergoing relativistic motion can create particles from quantum
vacuum fluctuations in a phenomenon known as the dynamical Casimir effect. We
examine the creation of particles, and more generally the transformation of
quantum field states, due to boundary motion in curved spacetime. We provide a
novel method enabling the calculation of the effect for a wide range of
trajectories and spacetimes. We apply this to the experimental scenario used to
detect the dynamical Casimir effect, now adopting the Schwarzschild metric, and
find novel resonances in particle creation as a result of the spacetime
curvature. Finally, we discuss a potential enhancement of the effect for the
phonon field of a Bose-Einstein condensate.Comment: 17 pages, 0 figures, 2 appendice
Universal quantum modifications to general relativistic time dilation in delocalised clocks
The theory of relativity associates a proper time with each moving object via
its world line. In quantum theory however, such well-defined trajectories are
forbidden. After introducing a general characterisation of quantum clocks, we
demonstrate that, in the weak-field, low-velocity limit, all "good" quantum
clocks experience time dilation as dictated by general relativity when their
state of motion is classical (i.e. Gaussian). For nonclassical states of
motion, on the other hand, we find that quantum interference effects may give
rise to a significant discrepancy between the proper time and the time measured
by the clock. The universality of this discrepancy implies that it is not
simply a systematic error, but rather a quantum modification to the proper time
itself. We also show how the clock's delocalisation leads to a larger
uncertainty in the time it measures -- a consequence of the unavoidable
entanglement between the clock time and its center-of-mass degrees of freedom.
We demonstrate how this lost precision can be recovered by performing a
measurement of the clock's state of motion alongside its time reading.Comment: 7 + 10 pages. V3: accepted versio
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Variable-camber systems integration and operational performance of the AFTI/F-111 mission adaptive wing
The advanced fighter technology integration, the AFTI/F-111 aircraft, is a preproduction F-111A testbed research airplane that was fitted with a smooth variable-camber mission adaptive wing. The camber was positioned and controlled by flexing the upper skins through rotary actuators and linkages driven by power drive units. The wing camber and control system are described. The measured servoactuator frequency responses are presented along with analytical predictions derived from the integrated characteristics of the control elements. A mission adaptive wing system chronology is used to illustrate and assess the reliability and dependability of the servoactuator system during 1524 hours of ground tests and 145 hours of flight testing
Mechanization of and experience with a triplex fly-by-wire backup control system
A redundant three-axis analog control system was designed and developed to back up a digital fly-by-wire control system for an F-8C airplane. Forty-two flights, involving 58 hours of flight time, were flown by six pilots. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum-displacement (force) side stick. The operational reliability of the F-8 digital fly-by-wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed
Mechanization of and experience with a triplex fly-by-wire backup control system
A redundant three axis analog control system was designed and developed to back up a digital fly by wire control system for an F-8C airplane. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum displacement (force) side stick. The operational reliability of the F-8 digital fly by wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed
Flight test of a resident backup software system
A new fault-tolerant system software concept employing the primary digital computers as host for the backup software portion has been implemented and flight tested in the F-8 digital fly-by-wire airplane. The system was implemented in such a way that essentially no transients occurred in transferring from primary to backup software. This was accomplished without a significant increase in the complexity of the backup software. The primary digital system was frame synchronized, which provided several advantages in implementing the resident backup software system. Since the time of the flight tests, two other flight vehicle programs have made a commitment to incorporate resident backup software similar in nature to the system described in this paper
The Consequences of Astroturf Lobbying for Trust and Authenticity:Findings and Implications from an Experiment
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