scholarly journals Large-scale structure non-Gaussianities with modal methods

2014 ◽  
Vol 11 (S308) ◽  
pp. 67-68
Author(s):  
Marcel Schmittfull
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
3D Structure ◽  
Computational Cost ◽  
Effective Field ◽  
Modal Expansion ◽  
Large Scale Structures ◽  
Bispectrum Estimation ◽  
Scale Structures ◽  
Non Gaussian

AbstractRelying on a separable modal expansion of the bispectrum, the implementation of a fast estimator for the full bispectrum of a 3d particle distribution is presented. The computational cost of accurate bispectrum estimation is negligible relative to simulation evolution, so the bispectrum can be used as a standard diagnostic whenever the power spectrum is evaluated. As an application, the time evolution of gravitational and primordial dark matter bispectra was measured in a large suite of N-body simulations. The bispectrum shape changes characteristically when the cosmic web becomes dominated by filaments and halos, therefore providing a quantitative probe of 3d structure formation. Our measured bispectra are determined by ∼ 50 coefficients, which can be used as fitting formulae in the nonlinear regime and for non-Gaussian initial conditions. We also compare the measured bispectra with predictions from the Effective Field Theory of Large Scale Structures (EFTofLSS).

scholarly journals Super-resolution emulator of cosmological simulations using deep physical models

2020 ◽  
Vol 495 (4) ◽  
pp. 4227-4236 ◽  
Author(s):  
Doogesh Kodi Ramanah ◽  
Tom Charnock ◽  
Francisco Villaescusa-Navarro ◽  
Benjamin D Wandelt
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Computational Cost ◽  
Physical Modelling ◽  
Real Space ◽  
Physical Models ◽  
Small Scale ◽  
Cosmological Simulations ◽  
Scale Structures ◽  
Small Scale Structures

ABSTRACT We present an extension of our recently developed Wasserstein optimized model to emulate accurate high-resolution (HR) features from computationally cheaper low-resolution (LR) cosmological simulations. Our deep physical modelling technique relies on restricted neural networks to perform a mapping of the distribution of the LR cosmic density field to the space of the HR small-scale structures. We constrain our network using a single triplet of HR initial conditions and the corresponding LR and HR evolved dark matter simulations from the quijote suite of simulations. We exploit the information content of the HR initial conditions as a well-constructed prior distribution from which the network emulates the small-scale structures. Once fitted, our physical model yields emulated HR simulations at low computational cost, while also providing some insights about how the large-scale modes affect the small-scale structure in real space.

scholarly journals The one-loop matter bispectrum in the Effective Field Theory of Large Scale Structures

2015 ◽  
Vol 2015 (10) ◽  
pp. 039-039 ◽  
Author(s):  
Raul E. Angulo ◽  
Simon Foreman ◽  
Marcel Schmittfull ◽  
Leonardo Senatore
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Large Scale ◽  
Effective Field ◽  
Large Scale Structures ◽  
Scale Structures ◽  
The One

scholarly journals How complex is the cosmic web?

2019 ◽  
Vol 491 (4) ◽  
pp. 5447-5463 ◽  
Author(s):  
F Vazza
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Magnetic Energy ◽  
Large Scale Structures ◽  
Dominant Component ◽  
Statistical Complexity ◽  
Statistical Sense ◽  
Scale Structures ◽  
Physical Laws ◽  
The Universe

ABSTRACT The growth of large-scale cosmic structure is a beautiful exemplification of how complexity can emerge in our Universe, starting from simple initial conditions and simple physical laws. Using enzo cosmological numerical simulations, I applied tools from Information Theory (namely, ‘statistical complexity’) to quantify the amount of complexity in the simulated cosmic volume, as a function of cosmic epoch and environment. This analysis can quantify how much difficult to predict, at least in a statistical sense, is the evolution of the thermal, kinetic, and magnetic energy of the dominant component of ordinary matter in the Universe (the intragalactic medium plasma). The most complex environment in the simulated cosmic web is generally found to be the periphery of large-scale structures (e.g. galaxy clusters and filaments), where the complexity is on average ∼10–102 times larger than in more rarefied regions, even if the latter dominate the volume-integrated complexity of the simulated Universe. If the energy evolution of gas in the cosmic web is measured on a ≈100 ${\rm kpc}\, h^{-1}$ resolution and over a ≈200 $\rm Myr$ time-scale, its total complexity is in the range of $\sim 10^{16}\!-\!10^{17} \rm \,bits$, with little dependence on the assumed gas physics, cosmology, or cosmic variance.

DENSITY PERTURBATIONS BY GLOBAL TEXTURES

1992 ◽  
Vol 01 (02) ◽  
pp. 427-437 ◽  
Author(s):  
MICHIYASU NAGASAWA ◽  
KATSUHIKO SATO
Keyword(s):  
Clustering Analysis ◽  
Large Scale ◽  
Dynamical Evolution ◽  
Conformal Time ◽  
Large Scale Structures ◽  
Cosmic Expansion ◽  
Density Perturbations ◽  
Scale Structures ◽  
Non Gaussian ◽  
The Universe

The dynamical evolution of global textures is studied. The evolution equation of a texture field is solved numerically and the effect of cosmic expansion is explicitly introduced. The process of knot collapse is traced and the knot number at conformal time, τ, per comoving volume is 0.01~0.02/τ3. The density perturbations by textures are investigated by a clustering analysis. High density clusters have large-scale correlation and extend widely, which enables the formation of large-scale structures. Moreover, the initial fluctuations by textures show the highly non-Gaussian spatial distribution. Thus they produce the density perturbations which may yield the cosmological structures in the universe.

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