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The 1+3 covariant approach and the covariant gauge-invariant approach to perturbations are used to analyze in depth conformal transformations in cosmology. Such techniques allow us to obtain very interesting insights on the physical content…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Sante Carloni , Emilio Elizalde , Sergei Odintsov

We present a new high-resolution N-body algorithm for cosmological simulations. The algorithm employs a traditional particle-mesh technique on a cubic grid and successive multilevel relaxations on the finer meshes, introduced recursively in…

Astrophysics · Physics 2009-10-30 Andrey V. Kravtsov , Anatoly A. Klypin , Alexei M. Khokhlov

Cosmological surveys aim at answering fundamental questions about our Universe, including the nature of dark matter or the reason of unexpected accelerated expansion of the Universe. In order to answer these questions, two important…

Cosmology and Nongalactic Astrophysics · Physics 2019-04-02 Xinyue Zhang , Yanfang Wang , Wei Zhang , Yueqiu Sun , Siyu He , Gabriella Contardo , Francisco Villaescusa-Navarro , Shirley Ho

In cosmology numerical simulations of structure formation are now of central importance, as they are the sole instrument for providing detailed predictions of current cosmological models for a whole class of important constraining…

Statistical Mechanics · Physics 2009-11-13 Michael Joyce

Detection and identification of nonlinearity is a task of high importance for structural dynamics. Detecting nonlinearity in a structure, which has been designed to operate in its linear region, might indicate the existence of damage.…

Machine Learning · Computer Science 2024-01-08 G. Tsialiamanis , C. R. Farrar

We present an algorithm for quickly generating multiple realizations of N-body simulations to be used, for example, for cosmological parameter estimation from surveys of large-scale structure. Our algorithm uses a new method to resample the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Michael D. Schneider , Shaun Cole , Carlos S. Frenk , Istvan Szapudi

The cold dark matter model has become the leading theoretical paradigm for the formation of structure in the Universe. Together with the theory of cosmic inflation, this model makes a clear prediction for the initial conditions for…

By directly probing the initial conditions of our universe, cosmological surveys offer us a unique observational handle on quantum field theory in curved spacetime with dynamical gravity and might even allow us to glean information about a…

The complexity and accuracy of current and future precision cosmology observational campaigns has made it essential to develop an efficient technique for directly combining simulation and observational datasets to determine cosmological and…

Astrophysics · Physics 2009-11-11 Katrin Heitmann , David Higdon , Charles Nakhleh , Salman Habib

We calculate the power spectrum of density fluctuations in the statistical non-equilibrium field theory for classical, microscopic degrees of freedom to first order in the interaction potential. We specialise our result to cosmology by…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-07 Matthias Bartelmann , Felix Fabis , Daniel Berg , Elena Kozlikin , Robert Lilow , Celia Viermann

We present results for the cosmic non-linear density-fluctuation power spectrum based on the analytical formalism developed in [1] which allows us to study cosmic structure formation based on Newtonian particle dynamics in phase-space. This…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-22 Tristan Daus , Elena Kozlikin

An attractive and simple hypothesis for the formation of large-scale structure is that it developed by gravitational instability from primordial fluctuations with an initially Gaussian probability distribution. Non-linear gravitational…

Astrophysics · Physics 2015-06-24 Ewa Luiza Lokas , Roman Juszkiewicz , David Weinberg , Francois Bouchet

Galaxy morphology, a key tracer of the evolution of a galaxy's physical structure, has motivated extensive research on machine learning techniques for efficient and accurate galaxy classification. The emergence of quantum computers has…

Astrophysics of Galaxies · Physics 2023-11-08 Mohammad Hassan Hassanshahi , Marcin Jastrzebski , Sarah Malik , Ofer Lahav

Reconstructing the initial conditions of the universe is a key problem in cosmology. Methods based on simulating the forward evolution of the universe have provided a way to infer initial conditions consistent with present-day observations.…

Cosmology and Nongalactic Astrophysics · Physics 2023-04-11 Ronan Legin , Matthew Ho , Pablo Lemos , Laurence Perreault-Levasseur , Shirley Ho , Yashar Hezaveh , Benjamin Wandelt

On the smallest scales, three-dimensional large-scale structure surveys contain a wealth of cosmological information which cannot be trivially extracted due to the non-linear dynamical evolution of the density field. Lagrangian perturbation…

Cosmology and Nongalactic Astrophysics · Physics 2015-08-05 Florent Leclercq , Jens Jasche , Héctor Gil-Marín , Benjamin Wandelt

We present a novel graph-based machine learning classifier for identifying the dark matter cosmic web environments of galaxies. Large galaxy surveys offer comprehensive statistical views of how galaxy properties are shaped by large-scale…

Astrophysics of Galaxies · Physics 2026-04-02 Dakshesh Kololgi , Krishna Naidoo , Amelie Saintonge , Ofer Lahav

We study the evolution of the universe which contains a multiple number of non-relativistic scalar fields decaying into both radiation and pressureless matter. We present a powerful analytic formalism to calculate the matter and radiation…

Astrophysics · Physics 2009-11-13 Ki-Young Choi , Jinn-Ouk Gong

Weak gravitational lensing is a powerful probe of cosmology, with second-order shear statistics commonly used to constrain parameters such as the matter density $\Omega_\mathrm{m}$ and the clustering amplitude $S_8$. However, parameter…

Cosmology and Nongalactic Astrophysics · Physics 2025-09-26 Niek Wielders , Laila Linke , Pierre A. Burger , Sven Heydenreich , Lucas Porth , Peter Schneider

We investigate cosmological structure formation seeded by topological defects which may form during a phase transition in the early universe. First we derive a partially new, local and gauge invariant system of perturbation equations to…

Astrophysics · Physics 2009-10-28 R. Durrer , Z. -H. Zhou

Fractals are geometric shapes that can display complex and self-similar patterns found in nature (e.g., clouds and plants). Recent works in visual recognition have leveraged this property to create random fractal images for model…

Computer Vision and Pattern Recognition · Computer Science 2023-03-23 Cheng-Hao Tu , Hong-You Chen , David Carlyn , Wei-Lun Chao