Probing Halo and Molecular States in Light, Neutron-Rich Nuclei

Selected topics on halo and molecular states in light, neutron-rich nuclei are discussed. In particular, work on $x\alpha$:X$n$ structures is briefly reviewed. The use of proton radiative capture as a probe of clustering is also presented through the example provided by the $^6$He(p,$\gamma$) reaction.Comment: Invited contribution to the International Symposium on Clustering Aspects of Quantum Many-Body Systems Kyoto, Japan, 12-14 November 2001 8 pages, 3 figure

Haloes and Clustering in Light, Neutron-Rich Nuclei

Clustering is a relatively widespread phenomena which takes on many guises across the nuclear landscape. Selected topics concerning the study of halo systems and clustering in light, neutron-rich nuclei are discussed here through illustrative examples taken from the Be isotopic chain.Comment: 5 pages, 5 figures Extended version of written contribution of invited talk to ENAM200

Nuclear Halo and Molecular States

Significant advances have been made in recent years in the exploration of clustering in light nuclei. This progress has arisen not only from the investigation of new systems, but also through the development and application of novel probes. This paper will briefly review selected topics concerning halo and molecular states in light nuclei through examples provided by the neutron-rich Be isotopes.Comment: 12 pages, 6 figures Invited paper to TOURS2000 Symposium Tours France, 4-7 Sept 2000 to be published as an AIP Conf. Proceeding

Clustering and Correlations at the Neutron Dripline

Some recent experimental studies of clustering and correlations within very neutron-rich light nuclei are reviewed. In particular, the development of the novel probes of neutron-neutron interferometry and Dalitz-plot analyses is presented through the example of the dissociation of the two-neutron halo system $^{14}$Be. The utility of high-energy proton radiative capture is illustrated using a study of the $^{6}$He(p,$\gamma$) reaction. A new approach to the production and detection of bound neutron clusters is also described, and the observation of events with the characteristics expected for tetraneutrons ($^{4}$n) liberated in the breakup of $^{14}$Be is discussed. The prospects for future work, including systems beyond the neutron dripline, are briefly outlined.Comment: Invited contribution to a topical issue on Exotic Nuclei of Les Comptes Rendus de l'Academie des Sciences Paris, Serie IV. 29 pages,11 figures (format RevTex preprint

A comparison of UK equity and property duration

This paper considers the duration of property and equity. A general formula for duration of asset classes is derived. It is shown that calculations which assume, usually implicitly, that the flow-through of inflation to cash flow is zero, produce misleadingly high durations for property and equities. These are typically in the range 15 to 25 years. Simulations using the formulae show that property has some bond-like characteristics. The results indicate that, for realistic flow-through rates, equities have a higher duration than property. The flow-through rate is the most important variable in the estimation of equities. Using historical data, equity duration is estimated at 8.65 years and property’s at 3.15 years. These are substantially lower than those commonly cited. If these values can be substantiated, and if higher values are used in practice, portfolio immunisation strategies may need to be reconsidered

Neutron-Neutron Correlations in the Dissociation of Halo Nuclei

Studies attempting to probe the spatial configuration of the valence neutrons in two-neutron halo nuclei using the technique of intensity interferometry are described. Following a brief review of the method and its application to earlier measurements of the breakup of 6He, 11Li and 14Be, the results of the analysis of a high statistics data set for 6He are presented. The limitations of the technique, including the assumption of incoherent emission in the breakup and the sensitivity to the continuum states populated in the dissociation rather than the ground state, are discussed.Comment: Revised and updated version of invited contribution to the RCNP Spring Workshop on Cluster Condensation and Nucleon Correlations -- 14 pages, 5 figure

On the role of vortex stretching in energy optimal growth of three dimensional perturbations on plane parallel shear flows

The three dimensional optimal energy growth mechanism, in plane parallel shear flows, is reexamined in terms of the role of vortex stretching and the interplay between the span-wise vorticity and the planar divergent components. For high Reynolds numbers the structure of the optimal perturbations in Couette, Poiseuille, and mixing layer shear profiles is robust and resembles localized plane-waves in regions where the background shear is large. The waves are tilted with the shear when the span-wise vorticity and the planar divergence fields are in (out of) phase when the background shear is positive (negative). A minimal model is derived to explain how this configuration enables simultaneous growth of the two fields, and how this mutual amplification reflects on the optimal energy growth. This perspective provides an understanding of the three dimensional growth solely from the two dimensional dynamics on the shear plane

BeppoSAX LECS background subtraction techniques

We present 3 methods for the subtraction of non-cosmic and unresolved cosmic backgrounds observed by the Low-Energy Concentrator Spectrometer (LECS) on-board BeppoSAX. Removal of these backgrounds allows a more accurate modeling of the spectral data from point and small-scale extended sources. At high (>|25| degree) galactic latitudes, subtraction using a standard background spectrum works well. At low galactic latitudes, or in complex regions of the X-ray sky, two alternative methods are presented. The first uses counts obtained from two semi-annuli near the outside of the LECS field of view to estimate the background at the source location. The second method uses ROSAT Position Sensitive Proportional Counter (PSPC) all-sky survey data to estimate the LECS background spectrum for a given pointing position. A comparison of the results from these methods provides an estimate of the systematic uncertainties. For high galactic latitude fields, all 3 methods give 3 sigma confidence uncertainties of <0.9 10^-3 count/s (0.1-10 keV), or <1.5 10^-3 count/s (0.1-2 keV). These correspond to 0.1-2.0 keV fluxes of 0.7-1.8 and 0.5-1.1 10^-13 erg/cm2/s for a power-law spectrum with a photon index of 2 and photoelectric absorption of 3 10^20 and 3 10^21 atom/cm2, respectively. At low galactic latitudes, or in complex regions of the X-ray sky, the uncertainties are a factor ~2.5 higher.Comment: 13 pages. Accepted for publication in A&A