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We investigate primordial non-Gaussianity in the Inflation without an Inflaton (IWI) framework, where scalar perturbations are generated at second order by primordial gravitational waves in Einstein gravity on an exact de Sitter (dS)…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-17 Mariam Abdelaziz , Marisol Traforetti , Daniele Bertacca , Raul Jimenez , Sabino Matarrese , Angelo Ricciardone

We present a novel method for including the impact of massive neutrinos in cold dark matter N-body simulations. Our approach is compatible with widely employed Newtonian N-body codes and relies on only three simple modifications. First, we…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-05 Pol Heuschling , Christian Partmann , Christian Fidler

Realistic models of high-energy physics include multiple scalar fields. Renormalization requires that the fields have nonminimal couplings to the spacetime Ricci curvature scalar, and the couplings can be large at the energy scales of…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-21 David I. Kaiser , Edward A. Mazenc , Evangelos I. Sfakianakis

Inaccuracies in the initial conditions for cosmological N-body simulations could easily be the largest source of systematic error in predicting the non-linear large-scale structure. From the theory side, initial conditions are usually…

Cosmology and Nongalactic Astrophysics · Physics 2020-11-18 Michaël Michaux , Oliver Hahn , Cornelius Rampf , Raul E. Angulo

It is well known that enhancement in the primordial scalar perturbations over small scales generates detectable amplitudes of secondary gravitational waves (GWs), by sourcing the tensor perturbations at the second order. These stochastic…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-06 H. V. Ragavendra

In single-field inflationary models with a low sound speed, the orthogonal shape of the primordial bispectrum arises due to partial cancellations between equilateral-type shapes. This fact allows for a speed of sound c_s as low as about…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Sebastien Renaux-Petel

This technical paper describes a software package that was designed to produce initial conditions for large cosmological simulations in the context of the Horizon collaboration. These tools generalize E. Bertschinger's Grafic1 software to…

Astrophysics · Physics 2009-11-13 S. Prunet , C. Pichon , D. Aubert , D. Pogosyan , R. Teyssier , S. Gottloeber

We set forth a new method for generating model-agnostic, nonparametric priors for neutron star equation-of-state inference that are stable, causal and thermodynamically consistent by construction. This generalizes Gaussian processes to…

High Energy Astrophysical Phenomena · Physics 2026-05-12 Tyler Gorda , Oleg Komoltsev , Aleksi Kurkela , Eirik Sunde

We present an efficient \textit{ab initio} algorithm for quantum dynamics simulations of interacting systems that is based on the conditional decomposition of the many-body wavefunction [Phys. Rev. Lett. 113, 083003 (2014)]. Starting with…

Mesoscale and Nanoscale Physics · Physics 2019-02-27 Guillermo Albareda , Aaron Kelly , Angel Rubio

The bispectrum of the microwave background sky is a possible discriminator between inflationary and defect models of structure formation in the Universe. The bispectrum, which is the analogue of the temperature 3-point correlation function…

Astrophysics · Physics 2009-10-30 A. F. Heavens

Accurate modeling of nonlinearities in the galaxy bispectrum, the Fourier transform of the galaxy three-point correlation function, is essential to fully exploit it as a cosmological probe. In this paper, we present numerical and…

Cosmology and Nongalactic Astrophysics · Physics 2015-12-02 Nuala McCullagh , Donghui Jeong , Alexander S. Szalay

We calculate the scale dependence of the bispectrum and trispectrum in (quasi) local models of non-Gaussian primordial density perturbations, and characterize this scale dependence in terms of new observable parameters. They can help to…

Cosmology and Nongalactic Astrophysics · Physics 2010-10-12 Christian T. Byrnes , Mischa Gerstenlauer , Sami Nurmi , Gianmassimo Tasinato , David Wands

This paper tackles the challenge presented by small-data to the task of Bayesian inference. A novel methodology, based on manifold learning and manifold sampling, is proposed for solving this computational statistics problem under the…

Machine Learning · Statistics 2019-10-29 Christian Soize , Roger Ghanem

Conditional density estimation is complicated by multimodality, heteroscedasticity, and strong non-Gaussianity. Gaussian processes (GPs) provide a principled nonparametric framework with calibrated uncertainty, but standard GP regression is…

Machine Learning · Computer Science 2026-03-12 Vardaan Tekriwal , Mark D. Risser , Hengrui Luo , Marcus M. Noack

For predictive modeling relying on Bayesian inversion, fully independent, or ``mean-field'', Gaussian distributions are often used as approximate probability density functions in variational inference since the number of variational…

Methodology · Statistics 2023-07-14 Wyatt Bridgman , Reese Jones , Mohammad Khalil

We consider the model reduction problem for linear time-invariant dynamical systems having nonzero (but otherwise indeterminate) initial conditions. Building upon the observation that the full system response is decomposable as a…

Systems and Control · Computer Science 2017-01-04 Christopher A. Beattie , Serkan Gugercin , Volker Mehrmann

Conditional image generation has paved the way for several breakthroughs in image editing, generating stock photos and 3-D object generation. This continues to be a significant area of interest with the rise of new state-of-the-art methods…

Computer Vision and Pattern Recognition · Computer Science 2022-05-10 Vedant Singh , Surgan Jandial , Ayush Chopra , Siddharth Ramesh , Balaji Krishnamurthy , Vineeth N. Balasubramanian

The aim of this paper is to propose a novel methodology to deal with micro-structural boundary conditions for the analysis of granular materials. The response of the granular assembly is modelled through the discrete element method (DEM),…

Soft Condensed Matter · Physics 2017-02-27 J. Liu , E. Bosco , A. S. J. Suiker

We study the initial conditions for cosmological $N$-body simulations for precision cosmology. In general, Zel'dovich approximation has been applied for the initial conditions of $N$-body simulations for a long time. These initial…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Takayuki Tatekawa

We aim to address sparse-view reconstruction of a 3D scene by leveraging priors from large-scale vision models. While recent advancements such as 3D Gaussian Splatting (3DGS) have demonstrated remarkable successes in 3D reconstruction,…

Computer Vision and Pattern Recognition · Computer Science 2025-07-29 Hanyang Yu , Xiaoxiao Long , Ping Tan