Approximate initial data for binary black holes

We construct approximate analytical solutions to the constraint equations of general relativity for binary black holes of arbitrary mass ratio in quasicircular orbit. We adopt the puncture method to solve the constraint equations in the transverse-traceless decomposition and consider perturbations of Schwarzschild black holes caused by boosts and the presence of a binary companion. A superposition of these two perturbations then yields approximate, but fully analytic binary black hole initial data that are accurate to first order in the inverse of the binary separation and the square of the black holes' momenta.Comment: 13 pages, 4 figures, added comparison to numerical calculations, accepted to PR

Understanding and Developing Estimates Based on Practical Foundation Methods for Alaska\u27s Discontinuous Permafrost Region

This research uses a quantitative analysis to develop a family of curves and a calculator for potential foundation thresholds in the discontinuous permafrost region of Alaska. The United States Pacific Command (PACAF) is bolstering the region by advocating for the F-35, KC-46, and the newly proposed long-range bomber to be stationed in Alaska. These next generation aircrafts and warfighters will need new facilities and beddown plans to efficiently and effectively carry out their mission. The biggest obstacle in the region is permafrost; this unique polar phenomenon is found throughout the northern half of Alaska. Fairbanks in particular has multiple military bases that could benefit from knowing which foundation type would excel in the region. With the help of seven experts in construction, excavation, and geotechnical engineering fields, the researcher discussed methods of constructing a fictitious foundation located at Eielson AFB. The average regional cost per cubic yard of soil is $4.13; however, the average cost to excavate permafrost catapults to$11.50. With different types of proven foundations used in Alaska, all experts agreed that helical piles and thermosyphons are for extreme scenarios and would not be cost-effective in the discontinuous permafrost region. Concrete piles and excavation being the two true contenders for the area, the researcher discovered that excavating is superior to concrete piles until the volume of permafrost exceeds 94% of the construction site. Even though Fairbanks has one of the cheapest concrete batch plants in Alaska, excavating and hauling fill materials miles away is ultimately cheaper for the military

Trumpet slices of the Schwarzschild-Tangherlini spacetime

We study families of time-independent maximal and 1+log foliations of the Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black hole solution in D spacetime dimensions, for D >= 4. We identify special members of these families for which the spatial slices display a trumpet geometry. Using a generalization of the 1+log slicing condition that is parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and Shibata in the limit of maximal slicing. We also construct a numerical code that evolves the BSSN equations for D=5 in spherical symmetry using moving-puncture coordinates, and demonstrate that these simulations settle down to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR

Microwave ISM Emission Observed by WMAP

We investigate the nature of the diffuse Galactic emission in the Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial dust-correlated emission is observed at all WMAP frequencies, far exceeding the expected thermal dust emission in the lowest frequency channels (23, 33, 41 GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated synchrotron radiation, attributing the correlation to the natural association of relativistic electrons produced by SNae with massive star formation in dusty clouds, and deriving an upper limit of 5% on the contribution of Draine & Lazarian spinning dust at K-band (23 GHz). We pursue an alternative interpretation that much, perhaps most, of the dust-correlated emission at these frequencies is indeed spinning dust, and explore the spectral dependence on environment by considering a few specific objects as well as the full sky average. Models similar to Draine & Lazarian spinning dust provide a good fit to the full-sky data. The full-sky fit also requires a significant component with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K) gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and added references. 23 pages, 5 figures, 2 tables. Free-free haze map is available at http://skymaps.inf

Microwave ISM Emission in the Green Bank Galactic Plane Survey: Evidence for Spinning Dust

We observe significant dust-correlated emission outside of H II regions in the Green Bank Galactic Plane Survey (-4 < b < 4 degrees) at 8.35 and 14.35 GHz. The rising spectral slope rules out synchrotron and free-free emission as majority constituents at 14 GHz, and the amplitude is at least 500 times higher than expected thermal dust emission. When combined with the Rhodes (2.326 GHz), and WMAP (23-94 GHz) data it is possible to fit dust-correlated emission at 2.3-94 GHz with only soft synchrotron, free-free, thermal dust, and an additional dust-correlated component similar to Draine & Lazarian spinning dust. The rising component generally dominates free-free and synchrotron for \nu >~ 14 GHz and is overwhelmed by thermal dust at \nu > 60 GHz. The current data fulfill most of the criteria laid out by Finkbeiner et al. (2002) for detection of spinning dust.Comment: ApJ in press. 26 pages, 11 figures, figures jpeg compressed to save spac

Critical behaviour in the nonlinear elastic response of hydrogels

In this paper we study the elastic response of synthetic hydrogels to an applied shear stress. The hydrogels studied here have previously been shown to mimic the behaviour of biopolymer networks when they are sufficiently far above the gel point. We show that near the gel point they exhibit an elastic response that is consistent with the predicted critical behaviour of networks near or below the isostatic point of marginal stability. This point separates rigid and floppy states, distinguished by the presence or absence of finite linear elastic moduli. Recent theoretical work has also focused on the response of such networks to finite or large deformations, both near and below the isostatic point. Despite this interest, experimental evidence for the existence of criticality in such networks has been lacking. Using computer simulations, we identify critical signatures in the mechanical response of sub-isostatic networks as a function of applied shear stress. We also present experimental evidence consistent with these predictions. Furthermore, our results show the existence of two distinct critical regimes, one of which arises from the nonlinear stretch response of semi-flexible polymers.

A Review of Leadership Theory and Competency Frameworks

This report presents a review of leadership theory and competency frameworks that was commissioned to assist the development of the new National Occupational Standards in Management and Leadership. The report begins with a review of leadership theories and tracks their evolution over the past 70 years from the “great man” notion of heroic leaders, through trait theories, behaviourist theories, situational leadership, contingency theory and on to transactional and transformational leadership. Each of these offers some insights into the qualities of successful leaders, but there has been a shift in focus from the generic characteristics and behaviours of the individual to a recognition of the importance of responding to different situations and contexts and the leaders’ role in relation to followers. The review concludes with an introduction to the notion of “dispersed leadership” and a distinction between the process of “leadership” and the socially-constructed role of “leader”. The next section, on Leadership Models and Competency Frameworks, presents a range of leadership and management frameworks currently being used in organisations. These define the qualities required of people in leadership positions and help to inform the leadership development process. Seven private-sector, nine public sector and eight generic frameworks are discussed and web links to the full models included where available. The following section gives a brief overview of a selection of leadership development initiatives both associated with, and as alternatives to, a leadership competencies framework. The aim of this is to give an indication of how different techniques can be used to develop leadership capability within individuals and organisations and how this relates to the underlying philosophy of the programme. The section on Providing Governance, describes the key legal and ethical responsibilities of Directors and an indication of the kinds of skills, behaviours and values required to achieve these. The report concludes with a discussion of the competency framework approach to leadership and leadership development and a proposal as to alternative ways of addressing these issues. It is concluded that whilst this approach has its strengths, it leads to a particularly individualistic notion of leadership and a relatively prescribed approach to leadership development. The changing nature of work and society, it is argued, may demand new approaches that encourage a more collective and emergent view of leadership and leadership development and of sharing the role of “leader” more widely within organisations.Chase Consulting; Management Standards Centr

A Simple Family of Analytical Trumpet Slices of the Schwarzschild Spacetime

We describe a simple family of analytical coordinate systems for the Schwarzschild spacetime. The coordinates penetrate the horizon smoothly and are spatially isotropic. Spatial slices of constant coordinate time $t$ feature a trumpet geometry with an asymptotically cylindrical end inside the horizon at a prescribed areal radius $R_0$ (with $0<R_{0}\leq M$) that serves as the free parameter for the family. The slices also have an asymptotically flat end at spatial infinity. In the limit $R_{0}=0$ the spatial slices lose their trumpet geometry and become flat -- in this limit, our coordinates reduce to Painlev\'e-Gullstrand coordinates.Comment: 7 pages, 3 figure