261 research outputs found
Towards the Laboratory Search for Space-Time Dissipation
It has been speculated that gravity could be an emergent phenomenon, with
classical general relativity as an effective, macroscopic theory, valid only
for classical systems at large temporal and spatial scales. As in classical
continuum dynamics, the existence of underlying microscopic degrees of freedom
may lead to macroscopic dissipative behaviors. With the hope that such
dissipative behaviors of gravity could be revealed by carefully designed
experiments in the laboratory, we consider a phenomenological model that adds
dissipations to the gravitational field, much similar to frictions in solids
and fluids. Constraints to such dissipative behavior can already be imposed by
astrophysical observations and existing experiments, but mostly in lower
frequencies. We propose a series of experiments working in higher frequency
regimes, which may potentially put more stringent bounds on these models.Comment: 18 pages, 8 figure
Phonon-Plasmon Interaction in Metal-Insulator-Metal Localized Surface Plasmon Systems
We investigate theoretically and numerically the coupling between elastic and
localized surface plasmon modes in a system of gold nanocylinders separated
from a thin gold film by a dielectric spacer of few nanometers thickness. That
system supports plasmon modes confined in between the bottom of the
nanocylinder and the top of the gold film, which arise from the formation of
interference patterns by short-wavelength metal-insulator-metal propagating
plasmon. First we present the plasmonic properties of the system though
computer-simulated extinction spectra and field maps associated to the
different optical modes. Next a simple analytical model is introduced, which
allows to correctly reproduce the shape and wavelengths of the plasmon modes.
This model is used to investigate the efficiency of the coupling between an
elastic deformation and the plasmonic modes. In the last part of the paper, we
present the full numerical simulations of the phononic properties of the
system, and then compute the acousto-plasmonic coupling between the different
plasmon modes and five acoustic modes of very different shape. The efficiency
of the coupling is assessed first by evaluating the modulation of the resonance
wavelength, which allows comparison with the analytical model, and finally in
term of time-modulation of the transmission spectra on the full visible range,
computed for realistic values of the deformation of the nanoparticle.Comment: 12 pages, 9 figure
Nano-plasmonic near field phase matching of attosecond pulses
Nano-structures excited by light can enhance locally the electric field when tuned to plasmonic resonances. This phenomenon can be used to boost non-linear processes such as harmonic generation in crystals or in gases, Raman excitation, and four wave mixing. Here we present a theoretical investigation of the near-field phase matching of attosecond pulses emitted by high-order harmonic generation (HHG) of an atom immersed in a multi-cycle femtosecond infrared laser field and a spatially inhomogeneous plasmonic field. We demonstrate that the spatial inhomogeneity factor of the plasmonic field strongly affects the electron trajectory and recombination time which can be used to control the attosecond emission. For further insight into the plasmonic field effect, we monitor the phase of each quantum path as a function of the inhomogeneity strength. Moreover, we investigate the attosecond emission as a function of near-field phase matching effects. This is achieved by calculating the coherent field superposition of attosecond pulses emitted from various intensities or field inhomogeneities. Finally, far-field and near-field phase matching effects are combined to modulate the harmonic spectral phase towards the emission of a single attosecond pulse
Astrophysical science metrics for next-generation gravitational-wave detectors
The second generation of gravitational-wave detectors are being built and
tuned all over the world. The detection of signals from binary black holes is
beginning to fulfill the promise of gravitational-wave astronomy. In this work,
we examine several possible configurations for third-generation laser
interferometers in existing km-scale facilities. We propose a set of
astrophysically motivated metrics to evaluate detector performance. We measure
the impact of detector design choices against these metrics, providing a
quantitative cost-benefit analyses of the resulting scientific payoffs
Residual amplitude modulation in interferometric gravitational wave detectors
The effects of residual amplitude modulation (RAM) in laser interferometers using heterodyne sensing can be substantial and difficult to mitigate. In this work, we analyze the effects of RAM on a complex laser interferometer used for gravitational wave detection. The RAM introduces unwanted offsets in the cavity length signals and thereby shifts the operating point of the optical cavities from the nominal point via feedback control. This shift causes variations in the sensing matrix, and leads to degradation in the performance of the precision noise subtraction scheme of the multiple-degree-of-freedom control system. In addition, such detuned optical cavities produce an optomechanical spring, which also perturbs the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO (aLIGO) detectors, and show that the RAM expected in aLIGO will not limit its sensitivity
Plasmonic mode interferences and Fano resonances in Metal-Insulator-Metal nanostructured interface OPEN
International audienceMetal-insulator-metal systems exhibit a rich underlying physics leading to a high degree of tunability of their spectral properties. We performed a systematic study on a metal-insulator-nanostructured metal system with a thin 6 nm dielectric spacer and showed how the nanoparticle sizes and excitation conditions lead to the tunability and coupling/decoupling of localized and delocalized plasmonic modes. We also experimentally evidenced a tunable Fano resonance in a broad spectral window 600 to 800 nm resulting from the interference of gap modes with white light broad band transmitted waves at the interface playing the role of the continuum. By varying the incident illumination angle shifts in the resonances give the possibility to couple or decouple the localized and delocalized modes and to induce a strong change of the asymmetric Fano profile. All these results were confirmed with a crossed comparison between experimental and theoretical measurements, confirming the nature of different modes. The high degree of control and tunability of this plasmonically rich system paves the way for designing and engineering of similar systems with numerous applications. In particular, sensing measurements were performed and a figure of merit of 3.8 was recorded ranking this sensor among the highest sensitive in this wavelength range. Surface plasmon polariton (SPP) and Localized surface plasmon (LSP) have attracted numerous researchers due to their high technological potential. SPP's are surface waves confined near a metal dielectric interface that can propagate over large distances 1 , making them appealing for applications in biosens-ing 2,3. On the other hand LSP resonances can be defined as the localized resonance condition that massively enhances the electromagnetic field in the vicinity of a metal nanoparticle (NP), when the NP have dimensions much smaller than the excitation wavelength 4. LSP resonance is very sensitive to changes in the NP's dimensions, the dielectric constant of the surrounding media and the nature of the substrate. Because of intense local electrical field enhancements and sharp resonance excitation peaks, metallic NPs are of great interest for applications in surface enhanced Raman spectroscopy (SERS) 5 , chemical and biological sensors 3,6 , cancer treatment 7 and light harvesting 8–10. Recently, strong attention was paid to the potentials of SPP and LSP combinations by investigating metallic NPs on top of metallic thin films. Several studies on such systems have indeed shown the coupling and hybridization between localized and delocalized modes, and the effect of the thickness of the dielectric spacer. Those works have revealed that such coupled systems exhibit enhanced optical properties and larger tunability of their spectral properties compared to uncoupled systems 1,4,11–2
The effect of smoking on the duration of life with and without disability, Belgium 1997-2011
Background: Smoking is the single most important health threat yet there is no consistency as to whether non-smokers experience a compression of years lived with disability compared to (ex-)smokers. The objectives of the manuscript are (1) to assess the effect of smoking on the average years lived without disability (Disability Free Life Expectancy (DFLE)) and with disability (Disability Life Expectancy (DLE)) and (2) to estimate the extent to which these effects are due to better survival or reduced disability in never smokers. Methods. Data on disability and mortality were provided by the Belgian Health Interview Survey 1997 and 2001 and a 10 years mortality follow-up of the survey participants. Disability was defined as difficulties in activities of daily living (ADL), in mobility, in continence or in sensory (vision, hearing) functions. Poisson and multinomial logistic regression models were fitted to estimate the probabilities of death and the prevalence of disability by age, gender and smoking status adjusted for socioeconomic position. The Sullivan method was used to estimate DFLE and DLE at age 30. The contribution of mortality and of disability to smoking related differences in DFLE and DLE was assessed using decomposition methods. Results: Compared to never smokers, ex-smokers have a shorter life expectancy (LE) and DFLE but the number of years lived with disability is somewhat larger. For both sexes, the higher disability prevalence is the main contributing factor to the difference in DFLE and DLE. Smokers have a shorter LE, DFLE and DLE compared to never smokers. Both higher mortality and higher disability prevalence contribute to the difference in DFLE, but mortality is more important among males. Although both male and female smokers experience higher disability prevalence, their higher mortality outweighs their disability disadvantage resulting in a shorter DLE. Conclusion: Smoking kills and shortens both life without and life with disability. Smoking related disability can however not be ignored, given its contribution to the excess years with disability especially in younger age groups
Observation of Parametric Instability in Advanced LIGO
Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this Letter, we describe the first observation of parametric instability in a gravitational wave detector, and the means by which it has been removed as a barrier to progress
Observation of Parametric Instability in Advanced LIGO
Parametric instabilities have long been studied as a potentially limiting
effect in high-power interferometric gravitational wave detectors. Until now,
however, these instabilities have never been observed in a kilometer-scale
interferometer. In this work we describe the first observation of parametric
instability in an Advanced LIGO detector, and the means by which it has been
removed as a barrier to progress
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