1,400 research outputs found
Quantum interference phenomena in the Casimir effect
We propose a definitive test of whether plates involved in Casimir
experiments should be modeled with ballistic or diffusive electrons--a
prominent controversy highlighted by a number of conflicting experiments. The
unambiguous test we propose is a measurement of the Casimir force between a
disordered quasi-2D metallic plate and a three-dimensional metallic system at
low temperatures, in which disorder-induced weak localization effects modify
the well-known Drude result in an experimentally tunable way. We calculate the
weak localization correction to the Casimir force as a function of magnetic
field and temperature and demonstrate that the quantum interference suppression
of the Casimir force is a strong, observable effect. The coexistence of weak
localization suppression in electronic transport and Casimir pressure would
lend credence to the Drude theory of the Casimir effect, while the lack of such
correlation would indicate a fundamental problem with the existing theory. We
also study mesoscopic disorder fluctuations in the Casimir effect and estimate
the width of the distribution of Casmir energies due to disorder fluctuations.Comment: 9 pages, 9 figure
Non-analytic behavior of the Casimir force across a Lifshitz transition in a spin-orbit coupled material
We propose the Casimir effect as a general method to observe Lifshitz
transitions in electron systems. The concept is demonstrated with a planar
spin-orbit coupled semiconductor in a magnetic field. We calculate the Casimir
force between two such semiconductors and between the semiconductor and a metal
as a function of the Zeeman splitting in the semiconductor. The Zeeman field
causes a Fermi pocket in the semiconductor to form or collapse by tuning the
system through a topological Lifshitz transition. We find that the Casimir
force experiences a kink at the transition point and noticeably different
behaviors on either side of the transition. The simplest experimental
realization of the proposed effect would involve a metal-coated sphere
suspended from a micro-cantilever above a thin layer of InSb (or another
semiconductor with large -factor). Numerical estimates are provided and
indicate that the effect is well within experimental reach.Comment: 5 pages + 6 page supplement; 5 figure
The Virgo O3 run and the impact of the environment
Sources of geophysical noise (such as wind, sea waves and earthquakes) or of anthropogenic noise impact ground-based gravitational-wave interferometric detectors, causing transient sensitivity worsening and gaps in data taking. During the one year-long third observing run (O3: from April 01, 2019 to March 27, 2020), the Virgo Collaboration collected a statistically significant dataset, used in this article to study the response of the detector to a variety of environmental conditions. We correlated environmental parameters to global detector performance, such as observation range, duty cycle and control losses. Where possible, we identified weaknesses in the detector that will be used to elaborate strategies in order to improve Virgo robustness against external disturbances for the next data taking period, O4, currently planned to start at the end of 2022. The lessons learned could also provide useful insights for the design of the next generation of ground-based interferometers
Calibration of advanced Virgo and reconstruction of the detector strain h( t) during the observing run O3
The three advanced Virgo and LIGO gravitational wave detectors participated to the third observing run (O3) between 1 April 2019 15:00 UTC and 27 March 2020 17:00 UTC, leading to several gravitational wave detections per month. This paper describes the advanced Virgo detector calibration and the reconstruction of the detector strain h(t) during O3, as well as the estimation of the associated uncertainties. For the first time, the photon calibration technique as been used as reference for Virgo calibration, which allowed to cross-calibrate the strain amplitude of the Virgo and LIGO detectors. The previous reference, so-called free swinging Michelson technique, has still been used but as an independent cross-check. h(t) reconstruction and noise subtraction were processed online, with good enough quality to prevent the need for offline reprocessing, except for the two last weeks of September 2019. The uncertainties for the reconstructed h(t) strain, estimated in this paper in a 20-2000 Hz frequency band, are frequency independent: 5% in amplitude, 35 mrad in phase and 10 μs in timing, with the exception of larger uncertainties around 50 Hz
Fluctuation-dominated quantum oscillations in excitonic insulators
The realization of excitonic insulators in transition metal dichalcogenide
systems has opened the door to explorations of the exotic properties such a
state exhibits. We study theoretically the potential for excitonic insulators
to show an anomalous form of quantum oscillations: the de Haas-van Alphen
effect in an insulating system. We focus on the role of the interactions that
generate the energy gap and show that it is crucial to consider quantum
fluctuations that go beyond the mean field treatment. Remarkably, quantum
fluctuations can be dominant, and lead to quantum oscillations than are
significantly larger than those predicted using mean field theory. Indeed, in
experimentally accessible parameter regimes these fluctuation-generated quantum
oscillations can even be larger than what would be found for the corresponding
gapless system.Comment: 4+3 pages, 2+1 figure
Proof of principle of a fuel injector based on a magnetostrictive actuator
One of the goals of modern internal combustion engines is the NOx-soot trade-off, and this would be better achieved by a better control of the fuel injection. Moreover, this feature can be also useful for high-performance hydraulic systems. Actual fuel injection technology either allows only the control of the injection time or it is based on very complex mechanical-hydraulic systems, as in the case of piezo-actuators. This work describes the basic steps that brought the authors to the realization of a concept fuel injector based on a Terfenol-D magnetostrictive actuator that could overcome the previous issues, being both simple and controllable. The study provides the design, development, and a feasibility analysis of a magnetostrictive actuator for fuel injection, by providing a basic magneto-static analysis of the actuator, the adaptation of a suitable standard fuel injector, and its experimental testing in a lab environment, with different shapes and amplitude of the reference signal to follow
- …