Universal noise and Efimov physics

Probability distributions for correlation functions of particles interacting via random-valued fields are discussed as a novel tool for determining the spectrum of a theory. In particular, this method is used to determine the energies of universal N-body clusters tied to Efimov trimers, for even N, by investigating the distribution of a correlation function of two particles at unitarity. Using numerical evidence that this distribution is log-normal, an analytical prediction for the N-dependence of the N-body binding energies is made.Comment: 6 pages, 3 figures. Invited contribution to the 21st International Conference on Few-Body Problems in Physics (FB21

Baryon properties in meson mediums from lattice QCD

We present results for the ground-state mass shifts of octet baryons due to the presence of a medium of pions or kaons from a lattice QCD calculation performed at a single value of the quark mass, corresponding to a pion mass of $m_\pi$ ~ 390 MeV, and a spatial volume V ~ (4fm)^3. We use a canonical approach in which correlators are formed using a single baryon propagator and a fixed number of meson propagators, up to n=9. From the ground-state energies we calculate two- and three-body interaction parameters. We also extract combinations of low-energy constants by comparing our results to tree level chiral perturbation theory at non-zero isospin/kaon chemical potential.Comment: 7 pages, 3 figures, Proceedings of the 31st International Symposium on Lattice Field Theory (Lattice 2013), July 29 - August 3, 2013, Mainz, German

Vega's hot dust from icy planetesimals scattered inward by an outward-migrating planetary system

Vega has been shown to host multiple dust populations, including both hot exo-zodiacal dust at sub-AU radii and a cold debris disk extending beyond 100 AU. We use dynamical simulations to show how Vega's hot dust can be created by long-range gravitational scattering of planetesimals from its cold outer regions. Planetesimals are scattered progressively inward by a system of 5-7 planets from 30-60 AU to very close-in. In successful simulations the outermost planets are typically Neptune-mass. The back-reaction of planetesimal scattering causes these planets to migrate outward and continually interact with fresh planetesimals, replenishing the source of scattered bodies. The most favorable cases for producing Vega's exo-zodi have negative radial mass gradients, with sub-Saturn- to Jupiter-mass inner planets at 5-10 AU and outer planets of 2.5 to 20 Earth masses. The mechanism fails if a Jupiter-sized planet exists beyond ~15 AU because the planet preferentially ejects planetesimals before they can reach the inner system. Direct-imaging planet searches can therefore directly test this mechanism.Comment: Updated references. Accepted to MNRAS Letters. 5 pages, 4 figures. Blog post about the paper at http://planetplanet.net/2014/03/31/vega-a-planetary-poem

Lattice methods for strongly interacting many-body systems

Lattice field theory methods, usually associated with non-perturbative studies of quantum chromodynamics, are becoming increasingly common in the calculation of ground-state and thermal properties of strongly interacting non-relativistic few- and many-body systems, blurring the interfaces between condensed matter, atomic and low-energy nuclear physics. While some of these techniques have been in use in the area of condensed matter physics for a long time, others, such as hybrid Monte Carlo and improved effective actions, have only recently found their way across areas. With this topical review, we aim to provide a modest overview and a status update on a few notable recent developments. For the sake of brevity we focus on zero-temperature, non-relativistic problems. After a short introduction, we lay out some general considerations and proceed to discuss sampling algorithms, observables, and systematic effects. We show selected results on ground- and excited-state properties of fermions in the limit of unitarity. The appendix contains details on group theory on the lattice.Comment: 64 pages, 32 figures; topical review for J. Phys. G; replaced with published versio

N-body Efimov states from two-particle noise

The ground state energies of universal N-body clusters tied to Efimov trimers, for N even, are shown to be encapsulated in the statistical distribution of two particles interacting with a background auxiliary field at large Euclidean time when the interaction is tuned to the unitary point. Numerical evidence that this distribution is log-normal is presented, allowing one to predict the ground-state energies of the N-body system.Comment: Extended discussion of results; published versio

Management of Rural Water Services in Nicaragua: A Systematic Network Approach to Evaluating Stakeholder Alignment

Water sector literature attributes a substantial cause of rural water system failure in developing countries to poor alignment between water service stakeholders. This study aimed to investigate a means for assessing stakeholder alignment by comparing the systemic interaction of stakeholder values, where the term ‘stakeholder values’ refers to aspects stakeholders believe are necessary to ensure rural water services are sustainable. The research held focus groups with key stakeholder groups involved in the management of rural water infrastructure in Terrabona, Nicaragua, to identify stakeholder values, and then used cross-impact analysis to evaluate how these values interacted to form stakeholder value networks (SVNs). Using normalized betweenness centrality measures, the structures of SVNs were compared to determine alignment. Results from this study showed high levels of stakeholder alignment on the topics of water resources and technology for the sustainability of rural water systems, while there was marked nonalignment regarding the involvement of local government and organizations in the management of water infrastructure. This study offers compelling evidence for future studies to assess stakeholder alignment by identifying and structurally analyzing SVNs

Real Wage Chronology

We process information in a large number of Canadian wage contracts, signed over a period of several decades, to generate the long-run history of the real wage for each bargaining pair. We term these hitherto unexamined histories ‘chronologies’. We are able to generate 1574 continuous real wage chronologies and we examine the evolution of the real wage in each case. We explore the influence of productivity growth, the labour relations record of the pair, the influence of industry and region as well as the initial wage on the growth of the real wage rate over the decades in the sample. We also consider the relation between the mean and variance of the real wage contained in these chronologies.Wages, productivity, labour relations, compensating differentials,convergence.