Computational Methods in Multi-Messenger Astrophysics using Gravitational Waves and High Energy Neutrinos

This dissertation seeks to describe advancements made in computational methods for multi-messenger astrophysics (MMA) using gravitational waves GW and neutrinos during Advanced LIGO (aLIGO)’s first through third observing runs (O1-O3) and, looking forward, to describe novel computational techniques suited to the challenges of both the burgeoning MMA field and high-performance computing as a whole. The first two chapters provide an overview of MMA as it pertains to gravitational wave/high energy neutrino (GWHEN) searches, including a summary of expected astrophysical sources as well as GW, neutrino, and gamma-ray detectors used in their detection. These are followed in the third chapter by an in-depth discussion of LIGO’s timing system, particularly the diagnostic subsystem, describing both its role in MMA searches and the author’s contributions to the system itself. The fourth chapter provides a detailed description of the Low-Latency Algorithm for Multi-messenger Astrophysics (LLAMA), the GWHEN pipeline developed by the author and used in O2 and O3. Relevant past multi-messenger searches are described first, followed by the O2 and O3 analysis methods, the pipeline’s performance, scientific results, and finally, an in-depth account of the library’s structure and functionality. In particular, the author’s high-performance multi-order coordinates (MOC) HEALPix image analysis library, HPMOC, is described. HPMOC increases performance of HEALPix image manipulations by several orders of magnitude vs. naive single-resolution approaches while presenting a simple high-level interface and should prove useful for diverse future MMA searches. The performance improvements it provides for LLAMA are also covered. The final chapter of this dissertation builds on the approaches taken in developing HPMOC, presenting several novel methods for efficiently storing and analyzing large data sets, with applications to MMA and other data-intensive fields. A family of depth-first multi-resolution ordering of HEALPix images — DEPTH9, DEPTH19, and DEPTH40 — is defined, along with algorithms and use cases where it can improve on current approaches, including high-speed streaming calculations suitable for serverless compute or FPGAs. For performance-constrained analyses on HEALPix data (e.g. image analysis in multi-messenger search pipelines) using SIMD processors, breadth-first data structures can provide short-circuiting calculations in a data-parallel way on compressed data; a simple compression method is described with application to further improving LLAMA performance. A new storage scheme and associated algorithms for efficiently compressing and contracting tensors of varying sparsity is presented; these demuxed tensors (D-Tensors) have equivalent asymptotic time and space complexity to optimal representations of both dense and sparse matrices, and could be used as a universal drop-in replacement to reduce code complexity and developer effort while improving performance of existing non-optimized numerical code. Finally, the big bucket hash table (B-Table), a novel type of hash table making guarantees on data layout (vs. load factor), is described, along with optimizations it allows for (like hardware acceleration, online rebuilds, and hard realtime applications) that are not possible with existing hash table approaches. These innovations are presented in the hope that some will prove useful for improving future MMA searches and other data-intensive applications

Skyler and Bliss

Hong Kong remains the backdrop to the science fiction movies of my youth. The city reminds me of my former training in the financial sector. It is a city in which I could have succeeded in finance, but as far as art goes it is a young city, and I am a young artist. A frustration emerges; much like the mould, the artist also had to develop new skills by killing off his former desires and manipulating technology. My new series entitled HONG KONG surface project shows a new direction in my artistic research in which my technique becomes ever simpler, reducing the traces of pixelation until objects appear almost as they were found and photographed. Skyler and Bliss presents tectonic plates based on satellite images of the Arctic. Working in a hot and humid Hong Kong where mushrooms grow ferociously, a city artificially refrigerated by climate control, this series provides a conceptual image of a imaginary typographic map for survival. (Laurent Segretier

KEER2022

Avanttítol: KEER2022. DiversitiesDescripció del recurs: 25 juliol 202

The Wolfville Magic Winery Bus: a grounded theory approach to understanding the consumer view of winescape

The tourism literature uses two perspectives to understand the wine tourism, the micro approach (an individual winery) and the macro approach (the winery area/region). This study reveals the important role played by tour guides in linking the micro and macro perspectives, creating a social environment and mediating the winery experience

Alternative asset holdings by US pension funds since the 2008 financial crisis

Since the financial crisis of 2008, the percentage of alternative asset holdings by institutional investors has increased dramatically. The current study utilizes the Public Plans Database to analyze both the drivers and impacts of this increased allocation to alternative assets on US pension funds. The results indicate that there has been a significant divergence in the asset mixes of US pension funds since the 2008 financial crisis, with the largest adaptors of alternatives now holding one-third of their funds in these assets. Regression analysis shows that Funded Ratio and Actuarially Assumed Rate of Return are both negatively related to the adaptation of alternatives. Finally, the naïve simulation analysis shows that, despite the argued motivation for the adaptation of alternatives by market research, those funds that adapted the highest level of alternatives would have actually performed worse during the 2008 financial crisis than those funds that made only modest allocation changes since that time

Testing an extension to the model of acceptance of technology in household with undergraduate and graduate students of four universities in three global countries

Individual adoption of technology has been studied extensively in the workplace, but far less attention has been paid to adoption of technology in the household (Brown & Venkatesh, 2005). Obviously, mobile phone is now integrated into our daily life. Indeed, according to International Data Corporation (IDC), the market reached 1.472 billion mobile phones sold in the world in 2017 (ZDNet, 2018). In addition, according to Statista, there was 4.77 billion mobile phone users worldwide in 2017 while the population was reaching 7.6 billion people, and there will be 5.07 billion mobile phone users worldwide by 2019 (Statista, 2018). The purpose of this study is then to pursue the investigation on the determining factors that make such people around the world are so using the mobile phone. On the basis of the model of acceptance of technology in household (MATH) developed by Brown and Venkatesh (2005) to verify the determining factors in intention to adopt a computer in household by American people, this study extends this moderator-type research model to examine the determining factors in the use of mobile phone in household by undergraduate and graduate students from four universities within three countries over the world. Data were randomly gathered from 750 undergraduate and graduate students from Yaounde in Cameroon, Kinshasa in Congo, and New Brunswick in Canada who own a mobile phone. Data analysis was performed using the structural equation modeling software Partial Least Squares (PLS). The results revealed, among others, that two-third of the variables examined in the study, including the three new variables we added to the Brown and Venkatesh’s research model, showed to be determining factors in the use of mobile phone by undergraduate and graduate students

A third wave for entrepreneurship research: mending the split between causation and effectuation through complexity

In this paper we propose that the theoretical framework for understanding entrepreneurship of Effectuation as developed in Sarasvathy (2001) can be reframed as a subset of complexity management as proposed by Nason (2017). Doing so has five main advantages. Firstly, it places effectuation as part of the well-developed theory of complexity science. This in turn allows for a refinement of the concepts of effectuation as they are reframed in the language of the more widely studied concepts of complexity science. Secondly, it separates the false dichotomy between causation and effectuation and recasts it into complementary complicated and complex systems whose selection for appropriateness depends on the specific underlying context or system of the entrepreneurial venture. Thirdly, it expands the applicability of the concept of effectuation beyond the purview of the entrepreneur into general management regardless of the scope, scale or development of the business organization in question. Fourthly, it changes the discussion of the criticisms of effectuation by showing many criticisms are based on incorrect methodologies for examining complex systems and non-reductionist systems. Finally, the recasting of effectuation as a subset of complexity management, helps to reinforce that complexity is a valid concept to expand from the social sciences where it is well accepted into the business literature where the study of complexity is in many ways still in its nascent stages