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Based on direct numerical simulations and symmetry arguments, we show that the large-scale Fourier modes are useful tools to describe the flow structures and dynamics of flow reversals in Rayleigh-B\'enard convection (RBC). We observe that…

Chaotic Dynamics · Physics 2015-05-27 Mani Chandra , Mahendra K. Verma

As is well known, structure formation in the Universe at times after decoupling can be described by hydrodynamic equations. These are shown here to be equivalent to a generalization of the stochastic Kardar--Parisi--Zhang equation with…

General Relativity and Quantum Cosmology · Physics 2009-10-28 J. F. Barbero G. , A. Dominguez , T. Goldman , J. Perez-Mercader

Ultra-light scalar fields and their non-interacting class, the so-called fuzzy dark matter (FDM), are candidates for dark matter, introduced to solve the small-scale problems of the standard cold dark matter. In this paper, we address…

Cosmology and Nongalactic Astrophysics · Physics 2024-01-24 Hamed Manouchehri Kousha , Sina Hooshangi , Aliakbar Abolhasani

We present two related techniques to measure the two-point correlation function and the power spectrum with edge correction in any spatial dimensions. The underlying algorithm uses fast Fourier transforms for calculating the two-point…

Astrophysics · Physics 2009-11-11 István Szapudi , Jun Pan , Simon Prunet , Tamás Budavári

We examine fluctuations of vorticity excited by an external random force in two-dimensional fluid in the presence of a strong external shear flow. The problem is motivated by the analysis of big coherent vortices appearing as a consequence…

Fluid Dynamics · Physics 2024-03-07 Igor V. Kolokolov , Vladimir V. Lebedev

We analyze the behavior of an ensemble of inertial particles in a one-dimensional smooth Gaussian velocity field, in the limit of large inertia, but considering a finite correlation time for the random field. We derive in this limit a…

Statistical Mechanics · Physics 2009-11-13 Piero Olla , Raffaella Vuolo

An improved approach to updating the electric field in simulations of Coulomb gases using the local lattice technique introduced by Maggs and Rossetto, is described and tested. Using the Fast Fourier Transform (FFT) an independent…

Other Condensed Matter · Physics 2009-11-11 A. Duncan , R. D. Sedgewick , R. D. Coalson

In the theory of disordered systems the spectral form factor $S(\tau)$, the Fourier transform of the two-level correlation function with respect to the difference of energies, is linear for $\tau<\tau_c$ and constant for $\tau>\tau_c$. Near…

Condensed Matter · Physics 2009-10-28 E. Brézin , S. Hikami

Iterative Fast Fourier Transform methods are useful for calculating the fields in composite materials and their macroscopic response. By iterating back and forth until convergence, the differential constraints are satisfied in Fourier…

Numerical Analysis · Mathematics 2018-01-25 Hervé Moulinec , Pierre Suquet , Graeme W. Milton

Forward modeling the galaxy density within the Effective Field Theory of Large Scale Structure (EFT of LSS) enables field-level analyses that are robust to theoretical uncertainties. At the same time, they can maximize the constraining…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-08 Julia Stadler , Fabian Schmidt , Martin Reinecke , Matteo Esposito

The dominant paradigm in computational materials discovery relies on heavily parameterized deep architectures, including message-passing graph networks and equivariant models, that require millions of DFT-labeled training structures and…

Materials Science · Physics 2026-05-19 Pranoy Ray , Surya R. Kalidindi

(Abridged) I investigate statistical properties of one-dimensional fields in the universe such as the Lyman alpha forest and inverted line-of-sight densities. Because of gravitational clustering, the cosmic density field is already quite…

Astrophysics · Physics 2007-05-23 Hu Zhan

We present a new class of estimators for computing small-scale power spectra and bispectra in configuration-space via weighted pair- and triple-counts, with no explicit use of Fourier transforms. Particle counts are truncated at $R_0\sim…

Cosmology and Nongalactic Astrophysics · Physics 2019-12-30 Oliver H. E. Philcox , Daniel J. Eisenstein

We apply an orthogonalization procedure on the effective field theory of large scale structure (EFT of LSS) shapes, relevant for the angle-averaged bispectrum and non-Gaussian covariance of the matter power spectrum at one loop. Assuming…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-23 Daniele Bertolini , Mikhail P. Solon

Perturbation theory (PT) calculation of large-scale structure has been used to interpret the observed non-linear statistics of large-scale structure at the quasi-linear regime. In particular, the so-called standard perturbation theory (SPT)…

Cosmology and Nongalactic Astrophysics · Physics 2018-12-05 Atsushi Taruya , Takahiro Nishimichi , Donghui Jeong

Redshift-space distortions in galaxy surveys happen along the radial direction, breaking statistical translation invariance. We construct estimators for radial distortions that, using only Fast Fourier Transforms (FFTs) of the overdensity…

Cosmology and Nongalactic Astrophysics · Physics 2015-11-04 Roman Scoccimarro

We discuss the density fluctuations of a fluid due to zero point motion. These can be regarded as density fluctuations in the phonon vacuum state. We assume a linear dispersion relation with a fixed speed of sound and calculate the density…

Quantum Physics · Physics 2010-04-22 L. H. Ford , N. F. Svaiter

The specification of a covariance function is of paramount importance when employing Gaussian process models, but the requirement of positive definiteness severely limits those used in practice. Designing flexible stationary covariance…

Computation · Statistics 2024-05-01 Paul G. Beckman , Christopher J. Geoga

Rank-2 tensor fields of large-scale structure, e.g. a tensor field inferred from shapes of galaxies, open up a window to directly access 2-scalar, 2-vector and 2-tensor modes, where the scalar fields can be measured independently from the…

Cosmology and Nongalactic Astrophysics · Physics 2022-06-13 Toshiki Kurita , Masahiro Takada

We have developed a new three-dimensional algorithm, based on the standard P$^3$M method, for computing deflections due to weak gravitational lensing. We compare the results of this method with those of the two-dimensional planar approach,…

Astrophysics · Physics 2009-10-31 H. M. P. Couchman , Andrew J. Barber , Peter A. Thomas