ASAP – A sub-sampling approach for preserving topological structures modeled with geodesic topographic mapping

Topological data analysis tools enjoy increasing popularity in a wide range of applications, such as Computer graphics, Image analysis, Machine learning, and Astronomy for extracting information. However, due to computational complexity, processing large numbers of samples of higher dimensionality quickly becomes infeasible. This contribution is twofold: We present an efficient novel sub-sampling strategy inspired by Coulomb's law to decrease the number of data points in d-dimensional point clouds while preserving its homology. The method is not only capable of reducing the memory and computation time needed for the construction of different types of simplicial complexes but also preserves the size of the voids in d-dimensions, which is crucial e.g. for astronomical applications. Furthermore, we propose a technique to construct a probabilistic description of the border of significant cycles and cavities inside the point cloud. We demonstrate and empirically compare the strategy in several synthetic scenarios and an astronomical particle simulation of a dwarf galaxy for the detection of superbubbles (supernova signatures). (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)

Tracking the Temporal-Evolution of Supernova Bubbles in Numerical Simulations

The study of low-dimensional, noisy manifolds embedded in a higher dimensional space has been extremely useful in many applications, from the chemical analysis of multi-phase flows to simulations of galactic mergers. Building a probabilistic model of the manifolds has helped in describing their essential properties and how they vary in space. However, when the manifold is evolving through time, a joint spatio-temporal modelling is needed, in order to fully comprehend its nature. We propose a first-order Markovian process that propagates the spatial probabilistic model of a manifold at fixed time, to its adjacent temporal stages. The proposed methodology is demonstrated using a particle simulation of an interacting dwarf galaxy to describe the evolution of a cavity generated by a Supernov

Swarm Intelligence-based Extraction and Manifold Crawling Along the Large-Scale Structure

The distribution of galaxies and clusters of galaxies on the mega-parsec scale of the Universe follows an intricate pattern now famously known as the Large-Scale Structure or the Cosmic Web. To study the environments of this network, several techniques have been developed that are able to describe its properties and the properties of groups of galaxies as a function of their environment. In this work we analyze the previously introduced framework: 1-Dimensional Recovery, Extraction, and Analysis of Manifolds (1-DREAM) on N-body cosmological simulation data of the Cosmic Web. The 1-DREAM toolbox consists of five Machine Learning methods, whose aim is the extraction and modelling of 1-dimensional structures in astronomical big data settings. We show that 1-DREAM can be used to extract structures of different density ranges within the Cosmic Web and to create probabilistic models of them. For demonstration, we construct a probabilistic model of an extracted filament and move through the structure to measure properties such as local density and velocity. We also compare our toolbox with a collection of methodologies which trace the Cosmic Web. We show that 1-DREAM is able to split the network into its various environments with results comparable to the state-of-the-art methodologies. A detailed comparison is then made with the public code DisPerSE, in which we find that 1-DREAM is robust against changes in sample size making it suitable for analyzing sparse observational data, and finding faint and diffuse manifolds in low density regions

Swarming in stellar streams: Unveiling the structure of the Jhelum stream with ant colony-inspired computation

The halo of the Milky Way galaxy hosts multiple dynamically coherent substructures known as stellar streams that are remnants of tidally disrupted systems such as globular clusters (GCs) and dwarf galaxies (DGs). A particular case is that of the Jhelum stream, which is known for its complex morphology. Using the available data from Gaia DR3, we extracted a region on the sky that contains Jhelum. We then applied the novel Locally Aligned Ant Technique (LAAT) on the position and proper motion space of stars belonging to the selected region to highlight the stars that are closely aligned with a local manifold in the data and the stars belonging to regions of high local density. We find that the overdensity representing the stream in proper motion space is composed of two components, and show the correspondence of these two signals to the previously reported narrow and broad spatial components of Jhelum. We made use of the radial velocity measurements provided by the $S^5$ survey to confirm, for the first time, a separation between the two components in radial velocity. We show that the narrow and broad components have velocity dispersions of $4.84^{+1.23}_{-0.79}$~km/s and $19.49^{+2.19}_{-1.84}$~km/s, and metallicity dispersions of $0.15^{+0.18}_{-0.10}$ and $0.34^{+0.13}_{-0.09}$, respectively. These measurements, and the difference in component widths, could be explained with a scenario where Jhelum is the remnant of a GC embedded within a DG that were accreted onto the Milky Way during their infall. Although the properties of Jhelum can be explained with this merger scenario, other progenitors of the narrow component remain possible such as a nuclear star cluster or a DG. To rule these possibilities out, we would need more observational data of member stars of the stream. Our analysis highlights the importance of the internal structure of streams with regards to their formation history

Contesting constitutionalism: constitutional politics in Southeast Asia

In recent years the constitutional landscape of Southeast Asia has changed tremendously. Against a worldwide background of liberalization, globalization, and democratization, states in the region have begun to alter their constitutions, reinforcing human rights provisions, and putting in place institutional safeguards, such as constitutional courts and human rights commissions. On closer examination, however, the picture is very complex, with constitutional developments differing greatly between states. This book explores a range of current constitutional developments in the different states of Southeast Asia through a distinct political lens. Drawing on comparative and single case studies, it considers various constitutional areas, including constitution drafting, human rights, legal safeguards and the continuing role of the military, sets constitutional developments in the wider political and historical context of each country, and makes comparisons both with Western democracies and with other developing regions. The book concludes by assessing overall how far constitutional practices and trajectories are converging towards a liberal Western model or towards a distinctly Southeast Asian model

Politics and Constitutions in Southeast Asia

In recent years the constitutional landscape of Southeast Asia has changed tremendously. Against a worldwide background of liberalization, globalization, and democratization, states in the region have begun to alter their constitutions, reinforcing human rights provisions, and putting in place institutional safeguards, such as constitutional courts and human rights commissions. On closer examination, however, the picture is very complex, with constitutional developments differing greatly between states. This book explores a range of current constitutional developments in the different states of Southeast Asia through a distinct political lens. Drawing on comparative and single case studies, it considers various constitutional areas, including constitution drafting, human rights, legal safeguards and the continuing role of the military, sets constitutional developments in the wider political and historical context of each country, and makes comparisons both with Western democracies and with other developing regions. The book concludes by assessing overall how far constitutional practices and trajectories are converging towards a liberal Western model or towards a distinctly Southeast Asian model

Contesting constitutionalism: constitutional politics in Southeast Asia

In recent years the constitutional landscape of Southeast Asia has changed tremendously. Against a worldwide background of liberalization, globalization, and democratization, states in the region have begun to alter their constitutions, reinforcing human rights provisions, and putting in place institutional safeguards, such as constitutional courts and human rights commissions. On closer examination, however, the picture is very complex, with constitutional developments differing greatly between states. This book explores a range of current constitutional developments in the different states of Southeast Asia through a distinct political lens. Drawing on comparative and single case studies, it considers various constitutional areas, including constitution drafting, human rights, legal safeguards and the continuing role of the military, sets constitutional developments in the wider political and historical context of each country, and makes comparisons both with Western democracies and with other developing regions. The book concludes by assessing overall how far constitutional practices and trajectories are converging towards a liberal Western model or towards a distinctly Southeast Asian model

Constitutional politics in Southeast Asia: From contestation to constitutionalism?

Over the last twenty-five years the constitutional landscape of Southeast Asia has changed tremendously. As in the rest of the world, states in the region are dramatically altering their constitutions, often putting in place institutional safeguards for individual rights, such as constitutional courts and human rights commissions. Yet despite the numerous formal changes, actual constitutional practice in the region has been highly uneven. Four areas are particularly contested: constitutional drafting and design; individual and religious rights; the role of the military in constitutional politics; and the rule of law, courts and justice. How states in Southeast Asia resolve unfolding conflicts in these four areas will be critical to how constitutionalism evolves in the region. replacing traditional legal scholarship with a new perspective on how constitutional politics are contested in the region, this article seeks to advance the scholarly debate by delving deeply into the dynamics that underpin unfolding constitutionalism trajectories and assessing whether countries in the region are actually deepening constitutional practice in a Western liberal sense or whether the model that seems to be emerging is quite different

Democratization and post-Suharto Indonesia/ Edit. : Marco Bunte

xx, 323 hal. ; 23 cm

Democratization and post-Suharto Indonesia/ Edit. : Marco Bunte

xx, 323 hal. ; 23 cm