Testing Wavefunction Collapse Models using Parametric Heating of a Trapped Nanosphere

We propose a mechanism for testing the theory of collapse models such as continuous spontaneous localization (CSL) by examining the parametric heating rate of a trapped nanosphere. The random localizations of the center-of-mass for a given particle predicted by the CSL model can be understood as a stochastic force embodying a source of heating for the nanosphere. We show that by utilising a Paul trap to levitate the particle and optical cooling, it is possible to reduce environmental decoher- ence to such a level that CSL dominates the dynamics and contributes the main source of heating. We show that this approach allows measurements to be made on the timescale of seconds, and that the free parameter λcsl which characterises the model ought to be testable to values as low as 10^{−12} Hz.

Experimental measurements of the collisional absorption of XUV radiation in warm dense aluminium

The collisional (or free-free) absorption of soft x rays in warm dense aluminium remains an unsolved problem. Competing descriptions of the process exist, two of which we compare to our experimental data here. One of these is based on a weak scattering model, another uses a corrected classical approach. These two models show distinctly different behaviors with temperature. Here we describe experimental evidence for the absorption of 26-eV photons in solid density warm aluminium (Te≈1 eV). Radiative x-ray heating from palladium-coated CH foils was used to create the warm dense aluminium samples and a laser-driven high-harmonic beam from an argon gas jet provided the probe. The results indicate little or no change in absorption upon heating. This behavior is in agreement with the prediction of the corrected classical approach, although there is not agreement in absolute absorption value. Verifying the correct absorption mechanism is decisive in providing a better understanding of the complex behavior of the warm dense state.

Settlement Duration and Materiality:Formal Chronological Models for the Development of Barnhouse, a Grooved Ware Settlement in Orkney

Radiocarbon dating and Bayesian chronological modelling, undertaken as part of the investigation by the Times of Their Lives project into the development of Late Neolithic settlement and pottery in Orkney, has provided precise new dating for the Grooved Ware settlement of Barnhouse, excavated in 1985–91. Previous understandings of the site and its pottery are presented. A Bayesian model based on 70 measurements on 62 samples (of which 50 samples are thought to date accurately the deposits from which they were recovered) suggests that the settlement probably began in the later 32nd century cal bc (with Houses 2, 9, 3 and perhaps 5a), possibly as a planned foundation. Structure 8 – a large, monumental structure that differs in character from the houses – was probably built just after the turn of the millennium. Varied house durations and replacements are estimated. House 2 went out of use before the end of the settlement, and Structure 8 was probably the last element to be abandoned, probably during the earlier 29th century cal bc. The Grooved Ware pottery from the site is characterised by small, medium-sized, and large vessels with incised and impressed decoration, including a distinctive, false-relief, wavy-line cordon motif. A considerable degree of consistency is apparent in many aspects of ceramic design and manufacture over the use-life of the settlement, the principal change being the appearance, from c. 3025–2975 cal bc, of large coarse ware vessels with uneven surfaces and thick applied cordons, and of the use of applied dimpled circular pellets. The circumstances of new foundation of settlement in the western part of Mainland are discussed, as well as the maintenance and character of the site. The pottery from the site is among the earliest Grooved Ware so far dated. Its wider connections are noted, as well as the significant implications for our understanding of the timing and circumstances of the emergence of Grooved Ware, and the role of material culture in social strategies.