Conservative Scattering of Reissner-Nordstr\"om Black Holes at Third Post-Minkowskian Order

Using a recently developed effective field theory formalism for extreme mass ratios [2308.14832], we present a calculation of charged black hole scattering at third post-Minkowskian order. The charges and masses are kept arbitrary, and the result interpolates from the scattering of Schwarzschild to extremal charged black holes, and beyond to charged particles in electrodynamics -- agreeing with previously reported results in all such limits. The computation of the radial action is neatly organized in powers of the mass ratio. The probe (0SF) contributions are readily computed by direct integration of the radial momentum, and we use the effective field theory to compute the subleading (1SF) contributions via background-field Feynman rules supplemented by an operator encoding recoil of the background. Together these contributions completely determine the conservative physics at order~$\mathcal{O}(G^{3})$.Comment: 36 pages, 3 figure

Microgrids & District Energy: Pathways To Sustainable Urban Development

A microgrid is an energy system specifically designed to meet some of the energy needs of a group of buildings, a campus, or an entire community. It can include local facilities that generate electricity, heating, and/or cooling; store energy; distribute the energy generated; and manage energy consumption intelligently and in real time. Microgrids enable economies of scale that facilitate local production of energy in ways that can advance cost reduction, sustainability, economic development, and resilience goals. As they often involve multiple stakeholders, and may encompass numerous distinct property boundaries, municipal involvement is often a key factor for successful implementation. This report provides an introduction to microgrid concepts, identifies the benefits and most common road blocks to implementation, and discusses proactive steps municipalities can take to advance economically viable and environmentally superior microgrids. It also offers advocacy suggestions for municipal leaders and officials to pursue at the state and regional level. The contents are targeted to municipal government staff but anyone looking for introductory material on microgrids should find it useful

Gauge Invariant Propagators and States in Quantum Electrodynamics

We study gauge invariant states in QED, where states are understood in terms of data living on the boundary of gauge invariant path-integrals. This is done for both scalar and spinor QED, and for boundaries that are either time slices, or the boundaries of a 'causal diamond'. We discuss both the case where the gauge field falls off to zero at the boundaries, and the case of 'large gauge transformations', where it remains finite at the boundaries. The dynamics are discussed using the gauge-invariant propagator, describing motion of both the particles and the field between the boundaries. We demonstrate how the path-integral naturally generates a 'Coulomb-field' dressing factor for states living on time-slices, and how this is done without fixing any gauge. We show that the form of the dressing depends only on the nature of the boundaries. We also derive the analogous dressing for states defined on null infinity, showing both its Coulombic parts as well as soft-photon parts.Comment: 24 pages, 3 figure

Measuring discursive influence across scholarship

Assessing scholarly influence is critical for understanding the collective system of scholarship and the history of academic inquiry. Influence is multifaceted, and citations reveal only part of it. Citation counts exhibit preferential attachment and follow a rigid “news cycle” that can miss sustained and indirect forms of influence. Building on dynamic topic models that track distributional shifts in discourse over time, we introduce a variant that incorporates features, such as authorship, affiliation, and publication venue, to assess how these contexts interact with content to shape future scholarship. We perform in-depth analyses on collections of physics research (500,000 abstracts; 102 years) and scholarship generally (JSTOR repository: 2 million full-text articles; 130 years). Our measure of document influence helps predict citations and shows how outcomes, such as winning a Nobel Prize or affiliation with a highly ranked institution, boost influence. Analysis of citations alongside discursive influence reveals that citations tend to credit authors who persist in their fields over time and discount credit for works that are influential over many topics or are “ahead of their time.” In this way, our measures provide a way to acknowledge diverse contributions that take longer and travel farther to achieve scholarly appreciation, enabling us to correct citation biases and enhance sensitivity to the full spectrum of scholarly impact

Effective Field Theory for Extreme Mass Ratios

We derive an effective field theory describing a pair of gravitationally interacting point particles in an expansion in their mass ratio, also known as the self-force (SF) expansion. The 0SF dynamics are trivially obtained to all orders in Newton's constant by the geodesic motion of the light body in a Schwarzschild background encoding the gravitational field of the heavy body. The corrections at 1SF and higher are generated by perturbations about this configuration -- that is, the geodesic deviation of the light body and the fluctuation graviton -- but crucially supplemented by an operator describing the recoil of the heavy body as it interacts with the smaller companion. Using this formalism we compute new results at third post-Minkowskian order for the conservative dynamics of a system of gravitationally interacting massive particles coupled to a set of additional scalar and vector fields.Comment: 9 pages, 1 figur

Measuring Discursive Influence Across Scholarship

Assessing scholarly influence is critical for researchers surveying literature, institutions seeking to credit and support scholarly work, and understanding the history of academic inquiry. Influence is multi-faceted and citations reveal only part of it. Citation counts exhibit preferential attachment and follow a rigid ``news cycle’’ that can miss sustained and indirect forms of influence. Building on dynamic topic models that track distributional shifts in discourse over time, we introduce a novel variant that incorporates features such as authorship, affiliation, and publication venue to assess how these contexts interact with content to shape future scholarship. We perform in-depth analyses on collections of physics research (500K abstracts; 102 years) and scholarship generally (JSTOR: 2M full-text articles; 130 years). Our measure of document influence helps predict citations, and shows how outcomes such as winning a Nobel Prize or affiliation with a highly ranked institution boost influence. Analysis of citations alongside discursive influence reveals that citations tend to credit authors who persist in their fields over time, and discount credit for works that are influential over many topics or are ``ahead of their time’’. In this way, our measures provide a way to acknowledge diverse contributions that take longer and travel further to achieve scholarly appreciation, enabling us to correct citation biases and enhance sensitivity to the full spectrum of scholarly impact

Self-care support for children and adolescents with long-term conditions : the REfOCUS evidence synthesis

Background: Self-care support (e.g. education, training, peer/professional support) is intended to enhance the self-care capacities of children and young people, while simultaneously reducing the financial burden facing health-care systems. Objectives: To determine which models of self-care support for long-term conditions (LTCs) are associated with significant reductions in health utilisation and costs without compromising outcomes for children and young people. Design: Systematic review with meta-analysis. Population: Children and young people aged 0–18 years with a long-term physical or mental health condition (e.g. asthma, depression). Intervention: Self-care support in health, social care, educational or community settings. Comparator: Usual care. Outcomes: Generic/health-related quality of life (QoL)/subjective health symptoms and health service utilisation/costs. Design: Randomised/non-randomised trials, controlled before-and-after studies, and interrupted time series designs. Data sources: MEDLINE, EMBASE, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, ISI Web of Science, NHS Economic Evaluation Database, The Cochrane Library, Health Technology Assessment database, Paediatric Economic Database Evaluation, IDEAS, reference scanning, targeted author searches and forward citation searching. All databases were searched from inception to March 2015. Methods: We conducted meta-analyses, simultaneously plotting QoL and health utilisation effects. We conducted subgroup analyses for evidence quality, age, LTC and intervention (setting, target, delivery format, intensity). Results: Ninety-seven studies reporting 114 interventions were included. Thirty-seven studies reported adequate allocation concealment. Fourteen were UK studies. The vast majority of included studies recruited children and young people with asthma (n = 66, 68%). Four per cent of studies evaluated ‘pure’ self-care support (delivered through health technology without additional contact), 23% evaluated facilitated self-care support (≤ 2 hours’/four sessions’ contact), 65% were intensively facilitated (≥ 2 hours’/four sessions’ contact) and 8% were case management (≥ 2 hours’ support with multidisciplinary input). Self-care support was associated with statistically significant, minimal benefits for QoL [effect size (ES) –0.17, 95% confidence interval (CI) –0.23 to –0.11], but lacked clear benefit for hospital admissions (ES –0.05, 95% CI –0.12 to 0.03). This finding endured across intervention intensities and LTCs. Statistically significant, minimal reductions in emergency use were observed (ES –0.11, 95% CI –0.17 to –0.04). The total cost analysis was limited by the small number of data. Subgroup analyses revealed statistically significant, minimal reductions in emergency use for children aged ≤ 13 years (ES –0.10, 95% CI –0.17 to –0.04), children and young people with asthma (ES –0.12, 95% CI –0.18 to –0.06) and children and young people receiving ≥ 2 hours per four sessions of support (ES –0.10, 95% CI –0.17 to –0.03). Preliminary evidence suggested that interventions that include the child or young person, and deliver some content individually, may optimise QoL effects. Face-to-face delivery may help to maximise emergency department effects. Caution is required in interpreting these findings. Limitations: Identification of optimal models of self-care support is challenged by the size and nature of evidence available. The emphasis on meta-analysis meant that a minority of studies with incomplete but potentially relevant data were excluded. Conclusions: Self-care support is associated with positive but minimal effects on children and young people’s QoL, and minimal, but potentially important, reductions in emergency use. On current evidence, we cannot reliably conclude that self-care support significantly reduces health-care costs. Future work: Research is needed to explore the short- and longer-term effects of self-care support across a wider range of LTCs. Study registration: This study is registered as PROSPERO CRD42014015452. Funding: The National Institute for Health Research Health Services and Delivery Research programme

A study of the quantum-to-classical transition in gravity, and a study of the consequences of constraints in gauge theory path-integrals

In this thesis we discuss various aspects of low energy quantum gravity from a number of different angles. The ultimate goal we have in mind is to prepare ourselves for the upcoming wave of low-energy experiments which may test quantum gravity. In the first part of this thesis we remain within "conventional'' quantum theory. We start with a study of quantum decoherence via the emission of low energy gravitational radiation. We find that after sufficiently long times this radiation can completely decohere a matter system. In studying decoherence we needed a better understanding of gauge invariance and physical states in path-integrals with prescribed boundary data. We generalize the standard Faddeev-Popov procedure to fit this purpose, and in doing so we better understand the nature of electric fields around quantum charges. The analogous work is also done in linearized quantum gravity. This language is useful for analyzing the debate around a recently proposed gravitational-entanglement experiment. We do such an analysis, and ultimately agree that these experiments indeed test conventional quantum gravity. As a tangential project we study the interactions of quarks in a background gluon condensate, and show how this can cause confinement. In the second part of the thesis we study an "alternative'' quantum gravity theory, the Correlated WorldLine (CWL) theory. We study the theory perturbatively, and also make use of a large-N expansion to study it non-perturbatively. We apply our results to physical systems: verifying that two-path systems experience "path-bunching'' which suppresses superpositions of massive objects. We also predict a frequency band in the microhertz range where tests of CWL involving massive objects are expected to see a signature.Science, Faculty ofPhysics and Astronomy, Department ofGraduat