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The non-Gaussian part of the covariance matrix of the galaxy power spectrum involves the connected four-point correlation in Fourier space, i.e. trispectrum. This paper introduces a fast method to compute the non-Gaussian part of the…

Cosmology and Nongalactic Astrophysics · Physics 2023-11-07 Yosuke Kobayashi

We revisit the flat-sky approximation for evaluating the angular power spectra of projected random fields by retaining information about the correlations along the line of sight. With broad, overlapping radial window functions, these…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-16 Zucheng Gao , Zvonimir Vlah , Anthony Challinor

Angular power spectra are an important measure of the angular clustering of a given distribution. In Cosmology, they are applied to such vastly different observations as galaxy surveys that cover a fraction of the sky and the Cosmic…

Astrophysics · Physics 2007-11-15 Brett Hayes , Robert Brunner , Volodymyr Kindratenko

Previous research on the diagnosis of Bipolar disorder has mainly focused on resting-state functional magnetic resonance imaging. However, their accuracy can not meet the requirements of clinical diagnosis. Efficient multimodal fusion…

Computer Vision and Pattern Recognition · Computer Science 2024-01-17 Guoxin Wang , Sheng Shi , Shan An , Fengmei Fan , Wenshu Ge , Qi Wang , Feng Yu , Zhiren Wang

We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane subsystem of the SPHERE "VLT planet finder", which pushes the limits of current AO systems to shorter wavelengths, higher spatial resolution, and much improved…

We describe a fast, optimal estimator for measuring angular bispectra between two correlated weakly non-Gaussian fields ($Y$ and $Z$) from observational datasets, based on a separable modal bispectrum expansion. Our methodology is…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-26 Maresuke Shiraishi , Michele Liguori , James R. Fergusson , E. P. S. Shellard

We propose an efficient algorithm for the evaluation of the potential and its gradient of gravitational/electrostatic $N$-body systems, which we call particle mesh multipole method (PMMM or PM$^3$). PMMM can be understood both as an…

Instrumentation and Methods for Astrophysics · Physics 2014-10-20 Keigo Nitadori

We investigate the possibility of detecting in redshift surveys a hemispherical power asymmetry similar to that first reported in CMB observations. We assume the hemispherical asymmetry arises from a linear gradient in comoving coordinates…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-29 Zhongxu Zhai , Michael Blanton

We present efficient algorithms for CMB lensing simulation and power spectrum es- timation for flat-sky CMB polarization maps. We build a pure B-mode estimator to remedy E to B leakage due to partial sky coverage. We show that our…

Cosmology and Nongalactic Astrophysics · Physics 2013-11-14 Thibaut Louis , Sigurd Næss , Sudeep Das , Joanna Dunkley , Blake Sherwin

An inverse nonequispaced fast Fourier transform (iNFFT) is a fast algorithm to compute the Fourier coefficients of a trigonometric polynomial from nonequispaced sampling data. However, various applications such as magnetic resonance imaging…

Numerical Analysis · Mathematics 2025-06-09 Melanie Kircheis , Daniel Potts

Precision measurements of the Sunyaev-Zel'dovich effect in clusters of galaxies require excellent rejection of common-mode signals and wide frequency coverage. We describe an imaging, efficient, differential Fourier transform spectrometer…

Instrumentation and Methods for Astrophysics · Physics 2014-05-27 Alessandro Schillaci , Giuseppe D' Alessandro , Paolo de Bernardis , Silvia Masi , Camila Paiva Novaes , Massimo Gervasi , Mario Zannoni

Constructing a fast and efficient estimator for the B-mode power spectrum of cosmic microwave background (CMB) is of critical importance for CMB science. For a general CMB survey, the Quadratic Maximum Likelihood (QML) estimator for CMB…

Cosmology and Nongalactic Astrophysics · Physics 2021-11-17 Jiming Chen , Shamik Ghosh , Hao Liu , Larissa Santos , Wenjuan Fang , Siyu Li , Yang Liu , Hong Li , Jiaxin Wang , Le Zhang , Bin Hu , Wen Zhao

This paper shows that it is possible to improve the computational cost, the memory requirements and the accuracy of Quick Fourier Transform (QFT) algorithm for power-of-two FFT (Fast Fourier Transform) just introducing a slight modification…

Data Structures and Algorithms · Computer Science 2013-01-07 Lorenzo Pasquini

To obtain the initial pressure from the collected data on a planar sensor arrangement in Photoacoustic tomography, there exists an exact analytic frequency domain reconstruction formula. An efficient realization of this formula needs to…

Numerical Analysis · Mathematics 2015-01-14 Julian Schmid , Thomas Glatz , Behrooz Zabihian , Mengyang Liu , Wolfgang Drexler , Otmar Scherzer

We describe a simple but efficient method for deriving a consistent set of monopole and dipole corrections for multi-frequency sky map data sets, allowing robust parametric component separation with the same data set. The computational core…

Cosmology and Nongalactic Astrophysics · Physics 2014-12-01 I. K. Wehus , U. Fuskeland , H. K. Eriksen , A. J. Banday , C. Dickinson , T Ghosh , K. M. Gorski , C. R. Lawrence , J. P. Leahy , D. Maino , P. Reich , W. Reich

Accurate modeling of small-scale redshift-space clustering is crucial for full shape RSD analyses, where satellite galaxies contribute to 1-halo terms and Finger-of-God distortions. We investigate halo reconstruction based on the cylinder…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-14 Ryuichiro Hada , Teppei Okumura

A simple least-squares optimisation enables the determination of the spectrum for irregularly sampled data that is readily reconstructed using an adjoint transformation of the Non-Uniform Fast Fourier Transform (NFFT). This is an…

Numerical Analysis · Mathematics 2024-02-28 Michael Sorochan Armstrong , José Carlos Pérez-Girón , José Camacho , Regino Zamora

We compute the connected four point correlation function (the trispectrum in Fourier space) of cosmological density perturbations at one-loop order in Standard Perturbation Theory (SPT) and the Effective Field Theory of Large Scale…

Cosmology and Nongalactic Astrophysics · Physics 2016-07-06 Daniele Bertolini , Katelin Schutz , Mikhail P. Solon , Kathryn M. Zurek

Fast, high-order accurate algorithms for electromagnetic scattering from axisymmetric objects are of great importance when modeling physical phenomena in optics, materials science (e.g. meta-materials), and many other fields of applied…

Numerical Analysis · Mathematics 2019-05-22 Jun Lai , Michael O'Neil

We present a numerically cheap approximation to super-sample covariance (SSC) of large scale structure cosmological probes, first in the case of angular power spectra. It necessitates no new elements besides those used for the prediction of…

Cosmology and Nongalactic Astrophysics · Physics 2019-04-17 Fabien Lacasa , Julien Grain