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The interstellar medium (ISM) is a magnetised system in which transonic or supersonic turbulence is driven by supernova explosions. This leads to the production of intermittent, filamentary structures in the ISM gas density, whilst the…

Astrophysics of Galaxies · Physics 2018-01-31 Irina Makarenko , Anvar Shukurov , Robin Henderson , Luiz F. S. Rodrigues , Paul Bushby , Andrew Fletcher

We explore the impact of reionization topology on 21-cm statistics. Four reionization models are presented which emulate large ionized bubbles around over-dense regions (21CMFAST/ global-inside- out), small ionized bubbles in over-dense…

Cosmology and Nongalactic Astrophysics · Physics 2014-08-15 Catherine A. Watkinson , Jonathan R. Pritchard

Recently the numerical simulations of the process of reionization of the universe at z>6 have made a qualitative leap forward, reaching sufficient sizes and dynamic range to determine the characteristic scales of this process. This allowed…

The predictions of mean-field electrodynamics can now be probed using direct numerical simulations of random flows and magnetic fields. When modelling astrophysical MHD, it is important to verify that such simulations are in agreement with…

Data Analysis, Statistics and Probability · Physics 2018-09-12 Irina Makarenko , Paul Bushby , Andrew Fletcher , Robin Henderson , Nikolay Makarenko , Anvar Shukurov

We study the evolution of the hydrogen ionization field during the epoch of reionization (EoR) using semi-numerical simulations. By calculating the Minkowski functionals (MFs) of the 21cm brightness temperature field, which provides a…

Cosmology and Nongalactic Astrophysics · Physics 2019-11-14 Zhaoting Chen , Yidong Xu , Yougang Wang , Xuelei Chen

It is possible that the properties of HII regions during reionization depend sensitively on many poorly constrained quantities (the nature of the ionizing sources, the clumpiness of the gas in the IGM, the degree to which photo-ionizing…

A key physical quantity during reionization is the size of HII regions. Previous studies found a characteristic bubble size which increases rapidly during reionization, with apparent agreement between simulations and analytic excursion set…

Cosmology and Nongalactic Astrophysics · Physics 2016-10-07 Yin Lin , S. Peng Oh , Steven R. Furlanetto , P. M. Sutter

Topological properties of crystalline ice structures are studied by considering ring statistics, coordination sequences, and topological density of different ice phases. The coordination sequences (number of sites at topological distance k…

Chemical Physics · Physics 2017-09-13 Carlos P. Herrero , Rafael Ramirez

We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the…

Cosmology and Nongalactic Astrophysics · Physics 2016-01-13 Yougang Wang , Changbom Park , Yidong Xu , Xuelei Chen , Juhan Kim

The size distribution of ionized regions during the epoch of reionization -- a key ingredient in understanding the HI power spectrum observable by 21cm experiments -- can be modelled analytically using the excursion set formalism of random…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Aseem Paranjape , T. Roy Choudhury

Persistent homology has been applied to brain network analysis for finding the shape of brain networks across multiple thresholds. In the persistent homology, the shape of networks is often quantified by the sequence of $k$-dimensional…

Quantitative Methods · Quantitative Biology 2018-11-13 Hyekyoung Lee , Moo K. Chung , Hongyoon Choi , Hyejin Kang , Seunggyun Ha , Yu Kyeong Kim , Dong Soo Lee

In this paper we investigate the nature and distribution of large neutral regions during the late epoch of reionization. In the "bubble model" of reionization, the mass distribution of large ionized regions ("bubbles") during the early…

Cosmology and Nongalactic Astrophysics · Physics 2014-01-17 Yidong Xu , Bin Yue , Meng Su , Zuhui Fan , Xuelei Chen

Persistent homology is a fundamental tool in topological data analysis; however, it lacks methods to quantify the fragility or fineness of cycles, anticipate their formation or disappearance, or evaluate their stability beyond persistence.…

Algebraic Topology · Mathematics 2025-05-16 Pablo Hernández-García , Daniel Hernández Serrano , Darío Sánchez Gómez

During the EoR, the first stars and galaxies appear while creating ionized bubbles that will eventually percolate near z=6. These ionized bubbles and percolation process are nowadays under a lot of scrutiny since observations of the HI gas…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-14 Emilie Thélie , Dominique Aubert , Nicolas Gillet , Pierre Ocvirk

The evolution of topology and morphology of ionized or neutral hydrogen during different stages of the Epoch of Reionization (EoR) have the potential to provide us a great amount of information about the properties of the ionizing sources…

Cosmology and Nongalactic Astrophysics · Physics 2022-11-23 Aadarsh Pathak , Satadru Bag , Saswata Dasgupta , Suman Majumdar , Rajesh Mondal , Mohd Kamran , Prakash Sarkar

We characterize structures such as monotonicity, convexity, and modality in smooth regression curves using persistent homology. Persistent homology is a key tool in topological data analysis that detects higher-dimensional topological…

Algebraic Topology · Mathematics 2025-10-28 Satish Kumar , Subhra Sankar Dhar

The reionization of the Universe, it is believed, occurred by the growth of ionized regions (bubbles) in the neutral intergalactic medium (IGM). We study the possibility of detecting these bubbles in radio-interferometric observations of…

Astrophysics · Physics 2009-03-19 Kanan K. Datta , Somnath Bharadwaj , T. Roy Choudhury

The topology and geometry of random fields - in terms of the Euler characteristic and the Minkowski functionals - has received a lot of attention in the context of the Cosmic Microwave Background (CMB), as the detection of primordial…

Cosmology and Nongalactic Astrophysics · Physics 2019-10-02 Job Feldbrugge , Matti van Engelen , Rien van de Weygaert , Pratyush Pranav , Gert Vegter

We present the prospects of extracting information about the Epoch of Reionization by identifying the remaining neutral regions, referred to as islands, in tomographic observations of the redshifted 21-cm signal. Using simulated data sets…

Astrophysics of Galaxies · Physics 2019-09-23 Sambit K. Giri , Garrelt Mellema , Thomas Aldheimer , Keri L. Dixon , Ilian T. Iliev

This paper is a cursory study on how topological features are preserved within the internal representations of neural network layers. Using techniques from topological data analysis, namely persistent homology, the topological features of a…

Machine Learning · Computer Science 2022-08-16 Archie Shahidullah