Calculation of the static and dynamical correlation energy of pseudo-one-dimensional beryllium systems via a many-body expansion

Low-dimensional beryllium systems constitute interesting case studies for the test of correlation methods because of the importance of both static and dynamical correlation in the formation of the bond. Aiming to describe the whole dissociation curve of extended Be systems we chose to apply the method of increments (MoI) in its multireference (MR) formalism. However, in order to do so an insight into the wave function was necessary. Therefore we started by focusing on the description of small Be chains via standard quantum chemical methods and gave a brief analysis of the main characteristics of their wave functions. We then applied the MoI to larger beryllium systems, starting from the Be6 ring. First, the complete active space formalism (CAS-MoI) was employed and the results were used as reference for local MR calculations of the whole dissociation curve. Despite this approach is well established for the calculation of systems with limited multireference character, its application to the description of whole dissociation curves still requires further testing. After discussing the role of the basis set, the method was finally applied to larger rings and extrapolated to an infinite chain

The chemical equilibration volume: measuring the degree of thermalization

We address the issue of the degree of equilibrium achieved in a high energy heavy-ion collision. Specifically, we explore the consequences of incomplete strangeness chemical equilibrium. This is achieved over a volume V of the order of the strangeness correlation length and is assumed to be smaller than the freeze-out volume. Probability distributions of strange hadrons emanating from the system are computed for varying sizes of V and simple experimental observables based on these are proposed. Measurements of such observables may be used to estimate V and as a result the degree of strangeness chemical equilibration achieved. This sets a lower bound on the degree of kinetic equilibrium. We also point out that a determination of two-body correlations or second moments of the distributions are not sufficient for this estimation.Comment: 16 pages, 15 figures, revtex

Enhancing Tc in field-doped Fullerenes by applying uniaxial stress

Capitalizing on the two-dimensional nature of superconductivity in field-effect doped C60, we show that it should be possible to increase the transition temperature Tc by applying uniaxial stress perpendicular to the gate electrode. This method not only holds the promise of substantially enhancing Tc (by about 30 K per GPa), but also provides a sensitive check of the current understanding of superconductivity in the doped Fullerenes.Comment: 3 pages RevTe

Surfing waves of data in San Diego: Sophisticated analyses provide a broad view of human genetic diversity

A report on the 64th annual American Society of Human Genetics meeting held in San Diego, USA, 18-22 October, 2014

Myrtaceous shrub species respond to long-term decreasing groundwater levels on the Gnangara Groundwater Mound, northern Swan Coastal Plain

Analysis of four vegetation transects that were established on the Bassendean Dune System, northern Swan Coastal Plain classified 42 native plant species into four ‘habitat’ groups based on their preferred soil moisture regimes (Havel 1968). Using adult abundance and distribution data from three of these transects and an additional transect established in 1976, we investigated the various ecological responses of myrtaceous shrub species representing the four habitat groups to long-term (20-30 yr) decreasing groundwater and soil moisture levels. Myrtaceous shrubs were chosen for analysis because of their widespread occurrence and diversity on the Swan Coastal Plain, and because Myrtaceae is the only plant family to be represented in all four of Havel’s habitat categories. Myrtaceous species ‘tolerant of excessive wetness’ (Astartea fascicularis, Hypocalymma angustifolium, Pericalymma ellipticum, Regelia ciliata) are all shallow rooted (rooting depth < 1m), occur in winter-wet depressions, and displayed the greatest reduction in population size in response to decreasing groundwater levels. Species cateogorised as displaying ‘maximum development on dry sites’ (Eremaea pauciflora, Melaleuca scabra, Scholtzia involucrata) commonly occurred on the upper and mid-slopes of the transects, are deeper-rooted and varied in their population response to long-term declines in water availability. All three species probably rely to some extent on accessing soil moisture at depth (2-6 m) during summer drought. The scenario was similar for species ‘optimum on moist sites’ (M. seriata) and for species ‘without clear-cut site preferences’ (Calytrix flavescens). In the context of Havel’s four habitat categories, whether a particular habitat preference is ‘wet’ or ‘dry’ refers to availability of soil moisture, although to what soil depth and moisture levels are uncertain. Habitat preferences, based on soil moisture availability, may have no relevance to a species preferred groundwater regime and hence response to decreasing groundwater levels. A species’ groundwater requirements during periods of drought are dependent on their position in the landscape, summer groundwater depth and the species rooting depth

On the Number of Facets of Three-Dimensional Dirichlet Stereohedra III: Full Cubic Groups

We are interested in the maximum possible number of facets that Dirichlet stereohedra for three-dimensional crystallographic groups can have. The problem for non-cubic groups was studied in previous papers by D. Bochis and the second author (Discrete Comput. Geom. 25:3 (2001), 419-444, and Beitr. Algebra Geom., 47:1 (2006), 89-120). This paper deals with ''full'' cubic groups, while ''quarter'' cubic groups are left for a subsequent paper. Here, ''full'' and ''quarter'' refers to the recent classification of three-dimensional crystallographic groups by Conway, Delgado-Friedrichs, Huson and Thurston (math.MG/9911185, Beitr. Algebra Geom. 42.2 (2001), 475-507). Our main result in this paper is that Dirichlet stereohedra for any of the 27 full groups cannot have more than 25 facets. We also find stereohedra with 17 facets for one of these groups.Comment: 28 pages, 12 figures. Changes from v1: apart of some editing (mostly at the end of the introduction) and addition of references, an appendix has been added, which analyzes the case where the base point does not have trivial stabilize

Baryon stopping and hyperon enhancement in the improved dual parton model

We present an improved version of the dual parton model which contains a new realization of the diquark breaking mechanism of baryon stopping. We reproduce in this way the net baryon yield in nuclear collisions. The model, which also considers strings originating from diquark-antidiquark pairs in the nucleon sea, reproduces the observed yields of p and Lambda and their antiparticles and underestimates cascades by less than 50 %. However, Omega's are underestimated by a factor five. Agreement with data is restored by final state interaction, with an averaged cross-section as small as 0.14 mb. Hyperon yields increase significantly faster than antihyperons, in agreement with experiment.Comment: 40 pages, 18 postscript figure

Black Hole Cross Section at the Large Hadron Collider

Black hole production at the Large Hadron Collider (LHC) was first discussed in 1999. Since then, much work has been performed in predicting the black hole cross section. In light of the start up of the LHC, it is now timely to review the state of these calculations. We review the uncertainties in estimating the black hole cross section in higher dimensions. One would like to make this estimate as precise as possible since the predicted values, or lower limits, obtain for the fundamental Planck scale and number of extra dimensions from experiments will depend directly on the accuracy of the cross section. Based on the current knowledge of the cross section, we give a range of lower limits on the fundamental Planck scale that could be obtained at LHC energies.Comment: 28 pages, 9 figures, LaTeX; added references, corrected typos, expanded discussio