Simulating the symmetron: domain walls and symmetry-restoring impurities

In this paper we study the dynamics of relativistic domain walls in the presence of static symmetry-restoring impurities. The field theory is precisely the same as what is known to cosmologists as the "symmetron model", whereby the usual $\mathbb{Z}_2$ symmetry breaking potential is appended with a space-varying mass-term (the space-variation is set by the profile of the impurity, which we take to be a "tanh"-function). After presenting the outcomes of a suite of different numerical experiments we have three main results: (1) domain walls pin to impurities, (2) domain wall necklaces can be energetically preferred configurations, and (3) impurities significantly modifies the usual ${N}_{\rm dw}\propto t^{-1}$ scaling law for random networks of domain walls.Comment: 24 pages; 14 figure

Effective action approach to cosmological perturbations in dark energy and modified gravity

In light of upcoming observations modelling perturbations in dark energy and modified gravity models has become an important topic of research. We develop an effective action to construct the components of the perturbed dark energy momentum tensor which appears in the perturbed generalized gravitational field equations, {\delta}G_{\mu\nu} = 8{\pi}G{\delta}T_{\mu\nu} + {\delta}U_{\mu\nu} for linearized perturbations. Our method does not require knowledge of the Lagrangian density of the dark sector to be provided, only its field content. The method is based on the fact that it is only necessary to specify the perturbed Lagrangian to quadratic order and couples this with the assumption of global statistical isotropy of spatial sections to show that the model can be specified completely in terms of a finite number of background dependent functions. We present our formalism in a coordinate independent fashion and provide explicit formulae for the perturbed conservation equation and the components of {\delta}U_{\mu\nu} for two explicit generic examples: (i) the dark sector does not contain extra fields, L = L(g_{\mu\nu}) and (ii) the dark sector contains a scalar field and its first derivative L = L(g_{\mu\nu}, {\phi}, \nabla_{\mu}{\phi}). We discuss how the formalism can be applied to modified gravity models containing derivatives of the metric, curvature tensors, higher derivatives of the scalar fields and vector fields.Comment: Version accepted by JCAP. Typos corrected. Covariant decoupling conditions adde

U.S. Global Health Policy: Donor Funding for Health in Low- & Middle- Income Countries, 2001-2007

Compares 2001 and 2007 data on overseas development assistance from member states of the Organization for Economic Co-operation and Development and examines trends by donor, region, and sector, with a focus on health and its subsectors

Application of Smoothed Particle Hydrodynamics (SPH) in Nearshore Mixing: A Comparison to Laboratory Data

A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used to simulate the nearshore flow hydrodynamics. The wave induced dispersion and diffusion are determined for monochromatic waves with significant wave height of 0.12 m and the wave period of 1.2 sec (Sop=5%) based on WCSPH wave dynamics. The hydrodynamics of WCSPH model are compared to the laboratory results obtained from series of LDA measurements. The overall mixing coefficients across the nearshore are determined from WCSPH hydrodynamics. The mixing coefficients obtained are compared with the values determined from a series of fluorometric studies performed in a large-scale facility in DHI, Denmark. The results show that the wave profiles are in good agreement with the experimental data. The WCSPH model is proven to be well capable of estimating the dispersion across the nearshore

The Nonprofit Sector Capital Market in BC and Alberta

A nonprofit capital market that invests in triple bottom line returns is emerging in Canada. Stemming from individuals, foundations, and governments providing donations and grants to nonprofit organisations to support social and environmental services, the nonprofit capital market is growing and innovating, bringing the rigours of the business world to bear in maximising social impacts and leveraging available nonprofit capital in more effective ways. Because investors are demanding a triple bottom line return instead of simply financial profit maximisation, the nonprofit capital market frees up organisations to pursue a social and/or environmental return that is not constantly traded off with the need to maximise financial profits. The nonprofit capital market can be viewed as a model or at least a starting place for understanding a new kind of capital market for all ventures that would flow resources to projects that create sustainable wealth.This paper gives an overview of the Canadian nonprofit capital market, focusing on the nonprofit and social enterprise sectors, including the users of nonprofit capital, the nonprofit capital investors, and the financial products that make up the nonprofit capital market. It discusses several promising trends in the nonprofit capital market, including venture philanthropy, program-related investments, and government tax credits. These trends promise to provide more resources to expand the social and sustainable sectors, generating significant social, environmental, and economic wealth for Canadian society. This is the final report from BALTA research project A3- The Non Profit Sector Capital Market in BC and Alberta.BC-Alberta Social Economy Research Alliance (BALTA) ; Social Sciences and Humanities Research Council of Canada (SSHRC

Wave overtopping and toe scouring at a plain vertical seawall with shingle foreshore : a physical model study

This paper describes a physical model study to investigate the wave overtopping and toe scouring at a plain vertical wall with a shingle foreshore. A matrix of 180 experimental test conditions were performed in a 2D wave flume, with an approximate scale of 1:50. The study investigates the baseline overtopping characteristics at a plain vertical wall on an impermeable 1:20 foreshore slope and compares the results with two permeable 1:20 shingle beach foreshores with prototype d50 values of 13 mm, and 24 mm respectively. For impulsive wave conditions, it was found that the mean overtopping rate was reduced by factor 3 for the d50 of 13 mm, and a factor of 4 for the d50 of 24 mm. For non-impulsive waves, the reduction factors were 1.5 for d50 of 13 mm and 2 for d50 of 24 mm. Prior to this study, limited design guidance was available to predict the mean overtopping discharges and mean sediment rates at vertical seawalls on permeable shingle foreshores. Therefore, a new set of prediction formulae are proposed in this study, based on the new laboratory test results, and a comparison with the available prediction methods in literature for vertical seawalls subjected to both impulsive and non-impulsive wave conditions