1,090 research outputs found
Binary Black Hole Astrophysics with Gravitational Waves
Gravitational Waves (GWs) have quickly emerged as powerful, indispensabletools for studying gravity in the strong field regime and high-energy astrophysical
phenomena since they were first directly detected by the Laser Interferometer
Gravitational-Wave Observatory (LIGO) on September 14, 2015. Over the course
of this dissertation work gravitational-wave astronomy has begun to mature, going
from 11 GW observations when I began to 90 at the time of writing, just before
the next observing run begins. As the network of GW observatories continues to
grow and these observations become a regular occurrence, the entire population of
merging compact objects observed with GWs will provide a unique probe of the
astrophysics of their formation and evolution along with the cosmic expansion of
the universe. In this dissertation I present four studies that I have led using GWs
to better understand the astrophysics of the currently most detected GW source,
binary black holes (BBHs). We first present a novel data-driven technique to look for deviations from modeled gravitational waveforms in the data, coherent across
the network of observatories, along with an analysis of the first gravitational-
wave transient catalog (GWTC-1). The following three studies present the three
different approaches to modeling populations of BBHs, using parametric, semi-
parametric and non-parametric models. The first of these studies uses a parametric
model that imposes a gap in the mass distribution of black holes, looking for
evidence of effects caused by pair-instability supernovae. The second study
introduces a semi-parametric model that aims to take advantage of the benefits of
both parametric and non-parametric methods, by imposing a flexible perturbation
to an underlying simpler parametric description. This study was among the first
data-driven studies revealing possible structure in the mass distribution of BBHs
using GWTC-2, namely an additional peak at 10Mâ . The final study introduces
a novel non-parametric model for hierarchically inferring population properties of
GW sources, and performs the most comprehensive data-driven study of the BBH
population to date. This study is also the first that uses non-parametric models
to simultaneously infer the distributions of BBH masses, spins and redshifts. This
dissertation contains previously published and unpublished material
Multidisciplinary perspectives on Artificial Intelligence and the law
This open access book presents an interdisciplinary, multi-authored, edited collection of chapters on Artificial Intelligence (âAIâ) and the Law. AI technology has come to play a central role in the modern data economy. Through a combination of increased computing power, the growing availability of data and the advancement of algorithms, AI has now become an umbrella term for some of the most transformational technological breakthroughs of this age. The importance of AI stems from both the opportunities that it offers and the challenges that it entails. While AI applications hold the promise of economic growth and efficiency gains, they also create significant risks and uncertainty. The potential and perils of AI have thus come to dominate modern discussions of technology and ethics â and although AI was initially allowed to largely develop without guidelines or rules, few would deny that the law is set to play a fundamental role in shaping the future of AI. As the debate over AI is far from over, the need for rigorous analysis has never been greater. This book thus brings together contributors from different fields and backgrounds to explore how the law might provide answers to some of the most pressing questions raised by AI. An outcome of the CatĂłlica Research Centre for the Future of Law and its interdisciplinary working group on Law and Artificial Intelligence, it includes contributions by leading scholars in the fields of technology, ethics and the law.info:eu-repo/semantics/publishedVersio
Fictocritical Cyberfeminism: A Paralogical Model for Post-Internet Communication
This dissertation positions the understudied and experimental writing practice of fictocriticism as an analog for the convergent and indeterminate nature of âpost-Internetâ communication as well a cyberfeminist technology for interfering and in-tervening in metanarratives of technoscience and technocapitalism that structure contemporary media. Significant theoretical valences are established between twen-tieth century literary works of fictocriticism and the hybrid and ephemeral modes of writing endemic to emergent, twenty-first century forms of networked communica-tion such as social media. Through a critical theoretical understanding of paralogy, or that countercultural logic of deploying language outside legitimate discourses, in-volving various tactics of multivocity, mimesis and metagraphy, fictocriticism is ex-plored as a self-referencing linguistic machine which exists intentionally to occupy those liminal territories âsomewhere in among/between criticism, autobiography and fictionâ (Hunter qtd. in Kerr 1996). Additionally, as a writing practice that orig-inated in Canada and yet remains marginal to national and international literary scholarship, this dissertation elevates the origins and ongoing relevance of fictocriti-cism by mapping its shared aims and concerns onto proximal discourses of post-structuralism, cyberfeminism, network ecology, media art, the avant-garde, glitch feminism, and radical self-authorship in online environments. Theorized in such a matrix, I argue that fictocriticism represents a capacious framework for writing and reading media that embodies the self-reflexive politics of second-order cybernetic theory while disrupting the rhetoric of technoscientific and neoliberal economic forc-es with speech acts of calculated incoherence. Additionally, through the inclusion of my own fictocritical writing as works of research-creation that interpolate the more traditional chapters and subchapters, I theorize and demonstrate praxis of this dis-tinctively indeterminate form of criticism to empirically and meaningfully juxtapose different modes of knowing and speaking about entangled matters of language, bod-ies, and technologies. In its conclusion, this dissertation contends that the âcreative paranoiaâ engendered by fictocritical cyberfeminism in both print and digital media environments offers a pathway towards a more paralogical media literacy that can transform the terms and expectations of our future media ecology
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Policy options for food system transformation in Africa and the role of science, technology and innovation
As recognized by the Science, Technology and Innovation Strategy for Africa â 2024 (STISA-2024), science, technology and innovation (STI) offer many opportunities for addressing the main constraints to embracing transformation in Africa, while important lessons can be learned from successful interventions, including policy and institutional innovations, from those African countries that have already made significant progress towards food system transformation. This chapter identifies opportunities for African countries and the region to take proactive steps to harness the potential of the food and agriculture sector so as to ensure future food and nutrition security by applying STI solutions and by drawing on transformational policy and institutional innovations across the continent. Potential game-changing solutions and innovations for food system transformation serving people and ecology apply to (a) raising production efficiency and restoring and sustainably managing degraded resources; (b) finding innovation in the storage, processing and packaging of foods; (c) improving human nutrition and health; (d) addressing equity and vulnerability at the community and ecosystem levels; and (e) establishing preparedness and accountability systems. To be effective in these areas will require institutional coordination; clear, food safety and health-conscious regulatory environments; greater and timely access to information; and transparent monitoring and accountability systems
Forecasting the Past and Recalling the Future: Lemniscate Narratives in the Work of Richard Powers
Richard Powersâs multifaceted accounts of individuals navigating turbulent histories are relayed via nonlinear timelines, situating the future in relation to an imminent past. The charactersâ reassembly of pre-existing compositions, patterns, and traditions in self-styled configurations, engages with interlocking legacies whilst asserting their individual perspective on reality. Multiple analyses of Powersâs texts have focused on the permeable borders between interconnected genres, eras, and disciplines in relation to spliced or stereoscopic images of society. The six texts analysed in this comparative study depict twofold timelines intersecting in the present, creating a lemniscate form with a seemingly endless course of expansion. This comparative approach assesses the converging and diverging lemniscate narrative form and content of six texts written at different stages in Powersâs career. The thesis explores the purpose of each textâs proposed lemniscate temporal frame in relation to the reoccurring depictions of transmedial utopian fictions and a neocolonial US history. This synthesis of pre-existing forms, modernist, and postmodernist world views resembles a metamodernist or transglossic literary style. The tensions between individual and hegemonic ideologies are explored within the three comparative chapters, evaluating the similarities and differences between Powersâs treatment of music and science, innovation and neocolonialism, and individual and collective responses to autonomy in the Atomic Age US
Perturbative and non-perturbative analysis of defect correlators in AdS/CFT
In this thesis, we consider two approaches to the study of correlation
functions in one-dimensional defect Conformal Field Theories (dCFT), in
particular those defined by 1/2-BPS Wilson line defects in the three- and
four-dimensional superconformal theories relevant in the AdS/CFT
correspondence. In the first approach, we use the analytic conformal bootstrap
to evaluate two examples of defect correlators. The four-point correlator of
the displacement supermultiplet inserted on the 1/2-BPS Wilson line in ABJM
theory is computed to the third order in a strong-coupling expansion and
reproduces the explicit first-order Witten diagram calculations. The CFT
data are then extracted from this correlator, and the operator mixing is solved
at first order. Consequently, all-order results are derived for the part of the
correlator with the highest logarithm power, uniquely determining the
double-scaling limit. Then, the five-point correlator of -BPS operators
inserted on the 1/2-BPS Wilson line in super Yang-Mills are
studied. The superblocks are derived for all channels of the OPE, and the
five-point correlator is bootstrapped to first order in a strong coupling
expansion. The CFT data are then extracted, confirming that operator mixing
does not affect the first-order anomalous dimension. The second approach
considers the general structure of correlators in effective theories in
AdS. All scalar -point contact Witten diagrams for external operators of
integer conformal weight are computed. Effective theories in AdS defined by
an interaction Lagrangian with an arbitrary number of derivatives are then
considered and solved to first order using a new formalism of Mellin amplitudes
for 1d CFTs. Finally, the cusped Wilson line discretised action is presented as
an alternative way to obtain non-perturbative data: through Lattice Field
Theory.Comment: PhD Thesis: 210 pages, 27 figure
Science and Innovations for Food Systems Transformation
This Open Access book compiles the findings of the Scientific Group of the United Nations Food Systems Summit 2021 and its research partners. The Scientific Group was an independent group of 28 food systems scientists from all over the world with a mandate from the Deputy Secretary-General of the United Nations. The chapters provide science- and research-based, state-of-the-art, solution-oriented knowledge and evidence to inform the transformation of contemporary food systems in order to achieve more sustainable, equitable and resilient systems
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Healthy Diet: A Definition for the United Nations Food Systems Summit 2021
Metaverse. Old urban issues in new virtual cities
Recent years have seen the arise of some early attempts to build virtual cities,
utopias or affective dystopias in an embodied Internet, which in some respects appear to
be the ultimate expression of the neoliberal city paradigma (even if virtual). Although
there is an extensive disciplinary literature on the relationship between planning and
virtual or augmented reality linked mainly to the gaming industry, this often avoids design
and value issues. The observation of some of these early experiences - Decentraland,
Minecraft, Liberland Metaverse, to name a few - poses important questions and problems
that are gradually becoming inescapable for designers and urban planners, and allows
us to make some partial considerations on the risks and potentialities of these early virtual
cities
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