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Probing magnetic fields in astrophysical environments is both important and challenging. The Gradient Technique (GT) is a new tool for tracing magnetic fields, rooted in the properties of magnetohydrodynamic (MHD) turbulence and turbulent…

Astrophysics of Galaxies · Physics 2024-06-18 Yue Hu , Alex Lazarian

Magnetohydrodynamic(MHD) turbulence displays velocity anisotropies which reflect the direction of the magnetic field. This anisotropy has led to the development of a number of statistical techniques for studying magnetic fields in the…

Probing magnetic fields in self-gravitating molecular clouds are generally difficult even with the use of the polarimetry. Based on the properties of magneto-hydrodynamic (MHD) turbulence and turbulent reconnection, Velocity Gradient…

Astrophysics of Galaxies · Physics 2019-03-01 Cheng-Han Hsieh , Yue Hu , Shih-Ping Lai , Ka Ho Yuen , Sheng-Yuan Liu , I-Ta Hsieh , Ka Wai Ho , Alex Lazarian

As a novel approach for tracing interstellar magnetic fields, the Velocity Gradient Technique (VGT) has been proven to be effective for probing magnetic fields in the diffuse interstellar medium (ISM). In this work, we verify the VGT in a…

Astrophysics of Galaxies · Physics 2022-01-26 Mingrui Liu , Yue Hu , Alex Lazarian

The observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-29 Yue Hu , Ka Ho Yuen , Alex Lazarian

Principal Component Analysis (PCA) is an efficient tool to optimize the multiparameter tests of general relativity (GR) where one tests for simultaneous deviations in multiple post-Newtonian (PN) phasing coefficients by introducing…

General Relativity and Quantum Cosmology · Physics 2022-08-17 Sayantani Datta , M. Saleem , K. G. Arun , B. S. Sathyaprakash

The detection of primordial B-mode polarization is still challenging due to the relatively low amplitude compared to the galactic foregrounds. To remove the contribution from the foreground, a comprehensive picture of the galactic magnetic…

Astrophysics of Galaxies · Physics 2020-07-07 Yue Hu , A. Lazarian

This study proceeds with the development of the technique employing velocity gradients that were identified in (\cite{GL17}, henceforth GL17) as a means of probing magnetic field in interstellar media. We demonstrate a number of practical…

Astrophysics of Galaxies · Physics 2017-05-25 Ka Ho Yuen , A. Lazarian

Magnetic fields play an important role in the evolution of molecular clouds and star formation. Using the Velocity Gradient Technique (VGT) model, we measured the magnetic field in Orion A using the 12CO, 13CO, and C18O (1-0) emission lines…

Recently years, the attempts on distilling mobile data into useful knowledge has been led to the deployment of machine learning algorithms at the network edge. Principal component analysis (PCA) is a classic technique for extracting the…

Information Theory · Computer Science 2022-04-04 Zezhong Zhang , Guangxu Zhu , Rui Wang , Vincent K. N. Lau , Kaibin Huang

In this work we investigate the Principal Component Analysis (PCA) sensitivity to the velocity power spectrum in high opacity regimes of the interstellar medium (ISM). For our analysis we use synthetic Position-Position-Velocity (PPV) cubes…

In recent years, Artificial Intelligence techniques have proved to be very successful when applied to problems in physical sciences. Here we apply an unsupervised Machine Learning (ML) algorithm called Principal Component Analysis (PCA) as…

Materials Science · Physics 2021-05-26 T. Tula , G. Möller , J. Quintanilla , S. R. Giblin , A. D. Hillier , E. E. McCabe , S. Ramos , D. S. Barker , S. Gibson

Principal components analysis (PCA) is a classical method for the reduction of dimensionality of data in the form of n observations (or cases) of a vector with p variables. For a simple model of factor analysis type, it is proved that…

Statistics Theory · Mathematics 2009-01-29 Iain M Johnstone , Arthur Yu Lu

In this study, we apply the Velocity Gradient Technique (VGT) to the merging Centaurus galaxy. We compare gradient maps derived from the PHANGS-ALMA survey using CO emission lines with magnetic field tracings from dust polarization data…

Astrophysics of Galaxies · Physics 2024-06-07 Quynh Lan Nguyen , Yue Hu , Alex Lazarian

Strong Alfv\'enic turbulence develops eddy-like motions perpendicular to the local direction of magnetic fields. This local alignment induces velocity gradients perpendicular to the local direction of the magnetic field. We use this fact to…

Astrophysics of Galaxies · Physics 2017-01-25 Diego F. González-Casanova , A. Lazarian

The advancement of our understanding of MHD turbulence opens ways to develop new techniques to probe magnetic fields. In MHD turbulence, the velocity gradients are expected to be perpendicular to magnetic fields and this fact was used by…

Astrophysics of Galaxies · Physics 2017-03-15 Ka Ho Yuen , A. Lazarian

Machine learning (ML) methods have proved to be a very successful tool in physical sciences, especially when applied to experimental data analysis. Artificial intelligence is particularly good at recognizing patterns in high dimensional…

Materials Science · Physics 2022-08-19 T. Tula , G. Möller , J. Quintanilla , S. R. Giblin , A. D. Hillier , E. E. McCabe , S. Ramos , D. S. Barker , S. Gibson

Principal Component Analysis (PCA) is a well-known multivariate technique used to decorrelate a set of vectors. PCA has been extensively applied in the past to the classification of stellar and galaxy spectra. Here we apply PCA to the…

Astrophysics · Physics 2007-05-23 I. Ferreras , B. Rogers , O. Lahav , .

Retrieval-Augmented Generation (RAG) has emerged as a powerful paradigm for grounding large language models in external knowledge sources, improving the precision of agents responses. However, high-dimensional language model embeddings,…

Machine Learning · Computer Science 2025-04-14 Arman Khaledian , Amirreza Ghadiridehkordi , Nariman Khaledian

Insights on stellar surface large-scale magnetic field topologies are usually drawn by applying Zeeman-Doppler-Imaging (ZDI) to the observed spectropolarimetric time series. However, ZDI requires experience for reliable results to be…

Solar and Stellar Astrophysics · Physics 2022-06-02 L. T. Lehmann , J. -F. Donati
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