Detecting a Z2Z_2 topologically ordered phase from unbiased infinite projected entangled-pair state simulations

We present an approach to identify topological order based on unbiased infinite projected entangled-pair states (iPEPS) simulations, i.e. where we do not impose a virtual symmetry on the tensors during the optimization of the tensor network ansatz. As an example we consider the ground state of the toric code model in a magnetic field exhibiting $Z_2$ topological order. The optimization is done by an efficient energy minimization approach based on a summation of tensor environments to compute the gradient. We show that the optimized tensors, when brought into the right gauge, are approximately $Z_2$ symmetric, and they can be fully symmetrized a posteriori to generate a stable topologically ordered state, yielding the correct topological entanglement entropy and modular S and U matrices. To compute the latter we develop a variant of the corner-transfer matrix method which is computationally more efficient than previous approaches based on the tensor renormalization group.Comment: 16 pages, 14 figure

Detection of child abuse by Dutch preventive child-healthcare doctors and nurses:Has it changed?

Abstract Objective Child maltreatment (i.e., abuse and neglect) is a major cause of child morbidity and death. It is a principal topic in community child-healthcare services yet little is known about the actual detection of suspected cases. We examined trends in this detection, as well as the characteristics of parents and children associated with higher rates of detection. Methods We obtained data on suspected cases of physical maltreatment, as well as of emotional and sexual abuse, from Dutch national samples for children aged 3 ¾ , 5-6 and 8-12 years, for 1997/98 and 2002/03 (response rates 92% and 84%, respectively, about 4,000 children each), as registered by preventive child-healthcare doctors and nurses. We assessed changes in the detection of suspected cases and also assessed the association of suspicion with the background characteristics of parents and children. Results Rates increased slightly over this 5-years period, from .23% to .41%, due to a quadrupling of suspected emotional abuse cases (from .06% to .24%), but without statistical significance. Suspicion of maltreatment was found to be more likely among boys, older children, and children with low-educated fathers and mothers who were younger than 27 years at the child’s birth. Conclusions Professionals in Dutch preventive child-healthcare services detected fewer cases of child maltreatment than might be expected on the basis of prevalence rates of self-reported maltreatment. Detection of other types of child maltreatment thus still needs further improvement in order to reach the goal of better child health.

275 George St, Brisbane

Author was lead Design Architect on project (Associate Director) for Crone Partners Architecture Studios. Building completed 2009

Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403

HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (= UGC 6456) resolve single stars down to M$_I$$\approx$-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter

Longitudinal links between childhood peer acceptance and the neural correlates of sharing

Childhood peer acceptance is associated with high levels of prosocial behavior and advanced perspective taking skills. Yet, the neurobiological mechanisms underlying these associations have not been studied. This functional magnetic resonance imaging study examined the neural correlates of sharing decisions in a group of adolescents who had a stable accepted status (n = 27) and a group who had a chronic rejected status (n = 19) across six elementary school grades. Both groups of adolescents played three allocation games in which they could share money with strangers with varying costs and profits to them and the other person. Stably accepted adolescents were more likely to share their money with unknown others than chronically rejected adolescents when sharing was not costly. Neuroimaging analyses showed that stably accepted adolescents, compared to chronically rejected adolescents, exhibited higher levels of activation in the temporo-parietal junction, posterior superior temporal sulcus, temporal pole, pre-supplementary motor area, and anterior insula during costly sharing decisions. These findings demonstrate that stable peer acceptance across childhood is associated with heightened activity in brain regions previously linked to perspective taking and the detection of social norm violations during adolescence, and thereby provide insight into processes underlying the widely established links between peer acceptance and prosocial behavior

Competition between intermediate plaquette phases in SrCu2_2(BO3_3)2_2 under pressure

Building on the growing evidence based on NMR, magnetization, neutron scattering, ESR, and specific heat that, under pressure, SrCu$_2$(BO$_3$)$_2$ has an intermediate phase between the dimer and the N\'eel phase, we study the competition between two candidate phases in the context of a minimal model that includes two types of intra- and inter-dimer interactions without enlarging the unit cell. We show that the empty plaquette phase of the Shastry-Sutherland model is quickly replaced by a quasi-1D full plaquette phase when intra- and/or inter-dimer couplings take different values, and that this full plaquette phase is in much better agreement with available experimental data than the empty plaquette one.Comment: 19 page

Assessing the Need for a Statewide Farmers’ Market Association in Maryland

Research is funded by a grant from the USDA Federal- State Marketing Improvement Program (FSMIP). FSMIP provides matching funds to State Departments of Agriculture, State agricultural experiment stations, and other appropriate State agencies to assist in exploring new market opportunities for U.S. food and agricultural products, and to encourage research and innovation aimed at improving the efficiency and performance of the marketing system

The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

We present deep Hubble Space Telescope single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. (1998) in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters which exhibit red horizontal branches, and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A, and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but lack the detection of main-sequence turnoffs which would provide unambiguous proof of ancient (>10 Gyr) stellar generations. Blue horizontal branch stars are above the detection limits, but difficult to distinguish from young stars with similar colors and magnitudes. Synthetic color-magnitude diagrams show it is possible to populate the blue horizontal branch in the halo of Leo A. The models also suggest ~50% of the total astrated mass in our pointing to be attributed to an ancient (>10 Gyr) stellar population. We conclude that Leo A started to form stars at least about 9 Gyr ago. Leo A exhibits an extremely low oxygen abundance, of only 3% of Solar, in its ionized interstellar medium. The existence of old stars in this very oxygen-deficient galaxy illustrates that a low oxygen abundance does not preclude a history of early star formation.Comment: 44 pages, 18 figures, accepted for publication in the August 2002 issue of AJ. High resolution figures is available at http://www.astro.spbu.ru/staff/dio/preprints.htm