Quantum Density Fluctuations in Classical Liquids

We discuss the density fluctuations of a fluid due to zero point motion. These can be regarded as density fluctuations in the phonon vacuum state. We assume a linear dispersion relation with a fixed speed of sound and calculate the density correlation function. We note that this function has the same form as the correlation function for the time derivative of a relativistic massless scalar field, but with the speed of light replaced by the speed of sound. As a result, the study of density fluctuations in a fluid can be a useful analog model for better understanding fluctuations in relativistic quantum field theory. We next calculate the differential cross section for light scattering by the zero point density fluctuations, and find a result proportional to the fifth power of the light frequency. This can be understood as the product of fourth power dependence of the usual Rayleigh cross section with the linear frequency dependence of the spectrum of zero point density fluctuations. We give some estimates of the relative magnitude of this effect compared to the scattering by thermal density fluctuations, and find that it can be of order 0.5% for water at room temperature and optical frequencies. This relative magnitude is proportional to frequency and inversely proportional to temperature. Although the scattering by zero point density fluctuation is small, it may be observable.Comment: 7 page

Anomalies in electrostatic calibrations for the measurement of the Casimir force in a sphere-plane geometry

We have performed precision electrostatic calibrations in the sphere-plane geometry and observed anomalous behavior. Namely, the scaling exponent of the electrostatic signal with distance was found to be smaller than expected on the basis of the pure Coulombian contribution and the residual potential found to be distance dependent. We argue that these findings affect the accuracy of the electrostatic calibrations and invite reanalysis of previous determinations of the Casimir force.Comment: 4 pages, 4 figure

SCOOTER: A compact and scalable dynamic labeling scheme for XML updates

Although dynamic labeling schemes for XML have been the focus of recent research activity, there are significant challenges still to be overcome. In particular, though there are labeling schemes that ensure a compact label representation when creating an XML document, when the document is subject to repeated and arbitrary deletions and insertions, the labels grow rapidly and consequently have a significant impact on query and update performance. We review the outstanding issues todate and in this paper we propose SCOOTER - a new dynamic labeling scheme for XML. The new labeling scheme can completely avoid relabeling existing labels. In particular, SCOOTER can handle frequently skewed insertions gracefully. Theoretical analysis and experimental results confirm the scalability, compact representation, efficient growth rate and performance of SCOOTER in comparison to existing dynamic labeling schemes

Complementary stereotyping of ethnic minorities predicts system justification in Poland

We investigate the phenomenon of complementary stereotyping of ethnic minorities in Poland and its relationship to system justification. Using results from a nationally representative survey we test the hypothesis that complementary stereotypes—according to which ethnic minorities are seen as possessing distinctive, offsetting strengths and weaknesses—would be associated with system justification among Polish majority citizens. For four minorities, results indicated that stereotyping them as (a) low in morality but high in competence or (b) high in morality but low in competence predicted greater system justification. These results suggest that even in a context that is low in support for the status quo, complementary stereotyping of ethnic minorities is linked to system justification processes. For the three minority groups that were lowest in social status, complementary stereotyping was unrelated to system justification. It appears that negative attitude towards these groups can be expressed openly, regardless of one’s degree of system justification

Towards a precision measurement of the Casimir force in a cylinder-plane geometry

We report on a proposal aimed at measuring the Casimir force in a cylinder-plane configuration. The Casimir force is evaluated including corrections due to finite parallelism, conductivity, and temperature. The range of validity of the proximity force approximation is also discussed. An apparatus to test the feasibility of a precision measurement in this configuration has been developed, and we describe both a procedure to control the parallelism and the results of the electrostatic calibration. Finally, we discuss the possibility of measuring the thermal contribution to the Casimir force and deviations from the proximity force approximation, both of which are expected at relatively large distances.Comment: 11 pages, 13 figures (.eps format, higher-resolution figures in published version

Theory of Exciton Migration and Field-Induced Dissociation in Conjugated Polymers

The interplay of migration, recombination, and dissociation of excitons in disordered media is studied theoretically in the low temperature regime. An exact expression for the photoluminescence spectrum is obtained. The theory is applied to describe the electric field-induced photoluminescence-quenching experiments by Kersting et al. [Phys. Rev. Lett. 73, 1440 (1994)] and Deussen et al. [Synth. Met. 73, 123 (1995)] on conjugated polymer systems. Good agreement with experiment is obtained using an on-chain dissociation mechanism, which implies a separation of the electron-hole pair along the polymer chain.Comment: 4 pages, RevTeX, 2 Postscript figure

Wavelength-selectable laser emission from a multistripe array grating integrated cavity laser

We report laser operation of a multistripe array grating integrated cavity (MAGIC) laser in which the wavelength of the emission from a single output stripe is chosen by selectively injection pumping a second stripe. We demonstrate a device that lases in the 1.5 µm fiber band at 15 wavelengths, evenly spaced by ~2 nm. The single-output/wavelength-selectable operation, together with the accurate predefinition of the lasing wavelengths, makes the MAGIC laser a very attractive candidate for use in multiwavelength networks