scholarly journals Non-linear cosmological power spectra in real and redshift space

1996 ◽  
Vol 282 (3) ◽  
pp. 767-778 ◽  
Author(s):  
A. N. Taylor ◽  
A. J. S. Hamilton
Keyword(s):  
Power Spectra ◽  
Non Linear

scholarly journals Kinetic field theory: Non-linear cosmic power spectra in the mean-field approximation

2021 ◽  
Vol 10 (6) ◽  
Author(s):  
Matthias Bartelmann ◽  
Johannes Dombrowski ◽  
Sara Konrad ◽  
Elena Kozlikin ◽  
Robert Lilow ◽  
...  
Keyword(s):  
Field Theory ◽  
Power Spectrum ◽  
Mean Field ◽  
Power Spectra ◽  
Field Approximation ◽  
Density Fluctuations ◽  
Mean Field Approximation ◽  
Non Linear ◽  
Two Parameters ◽  
Kinetic Field

We use the recently developed Kinetic Field Theory (KFT) for cosmic structure formation to show how non-linear power spectra for cosmic density fluctuations can be calculated in a mean-field approximation to the particle interactions. Our main result is a simple, closed and analytic, approximate expression for this power spectrum. This expression has two parameters characterising non-linear structure growth which can be calibrated within KFT itself. Using this self-calibration, the non-linear power spectrum agrees with results obtained from numerical simulations to within typically \lesssim10\,\%≲10% up to wave numbers k\lesssim10\,h\,\mathrm{Mpc}^{-1}k≲10hMpc−1 at redshift z = 0z=0. Adjusting the two parameters to optimise agreement with numerical simulations, the relative difference to numerical results shrinks to typically \lesssim 5\,\%≲5%. As part of the derivation of our mean-field approximation, we show that the effective interaction potential between dark-matter particles relative to Zel’dovich trajectories is sourced by non-linear cosmic density fluctuations only, and is approximately of Yukawa rather than Newtonian shape.

scholarly journals N-body simulations for parametrized modified gravity

2020 ◽  
Vol 497 (2) ◽  
pp. 1885-1894
Author(s):  
Farbod Hassani ◽  
Lucas Lombriser
Keyword(s):  
Modified Gravity ◽  
Full Range ◽  
Percent Level ◽  
Power Spectra ◽  
Large Field ◽  
Spherical Collapse ◽  
Non Linear ◽  
Normal Branch ◽  
Braneworld Model ◽  
Tests Of Gravity

ABSTRACT We present MG-evolution, an N-body code simulating the cosmological structure formation for parametrized modifications of gravity. It is built from the combination of parametrized linear theory with a parametrization of the deeply non-linear cosmological regime extrapolated from modified spherical collapse computations that cover the range of known screening mechanisms. We test MG-evolution, which runs at the speed of conventional ΛCDM simulations, against a suit of existing exact model-specific codes, encompassing linearized and chameleon f(R) gravity as well as the normal branch of the Dvali–Gabadadz–Porrati braneworld model, hence covering both large-field value and large-derivative screening effects. We compare the non-linear power spectra produced by the parametrized and model-specific approaches over the full range of scales set by the box size and resolution of our simulations, k = (0.05 − 2.5) $h\, \mathrm{Mpc}^{-1}$, and for two redshift slices, z = 0 and z = 1. We find sub-percent to one-percent level recovery of all the power spectra generated with the model-specific codes for the full range of scales. MG-evolution can be used for generalized and accurate tests of gravity and dark energy with the increasing wealth of high-precision cosmological survey data becoming available over the next decade.

Chaos and bifurcation analysis of a flexible rotor supported by short journal bearings with non-linear suspension

2000 ◽  
Vol 214 (7) ◽  
pp. 931-947 ◽  
Author(s):  
H-T Yau ◽  
C-K Chen ◽  
C-L Chen
Keyword(s):  
Chaotic Motion ◽  
Power Spectra ◽  
Rotor System ◽  
Numerical Results ◽  
Operating Conditions ◽  
Flexible Rotor ◽  
Bifurcation And Chaos ◽  
Symmetric Motion ◽  
Bifurcation Phenomenon ◽  
Non Linear

The bifurcation and chaos of the unbalanced response of a bearing-rotor system with non-linear suspension are investigated on the basis of the assumption of an incompressible lubricant together with short bearing approximation. Numerical results show that, owing to the non-linear factors, the trajectory of the journal centre demonstrates steady state symmetric motion even when the trajectory of the bearing centre is in a state of disorder. Poincaré maps, bifurcation diagrams and power spectra are used to analyse the behaviour of the bearing centre in the horizontal and vertical directions under different operating conditions. A unidirectional bifurcation phenomenon is detected in the bearing-rotor system in this study. The fractal dimension concept is used to determine whether the system is in a state of chaotic motion. Numerical results show that the dimension of the bearing centre trajectory is fractal and greater than 2 in some operating conditions. This indicates that the bearing centre is in the state of chaotic motion at these operating conditions.

scholarly journals On the road to per cent accuracy – II. Calibration of the non-linear matter power spectrum for arbitrary cosmologies

2019 ◽  
Vol 490 (4) ◽  
pp. 4826-4840 ◽  
Author(s):  
Benjamin Giblin ◽  
Matteo Cataneo ◽  
Ben Moews ◽  
Catherine Heymans
Keyword(s):  
Power Spectrum ◽  
Initial Conditions ◽  
Power Spectra ◽  
Linear Regime ◽  
The Road ◽  
Matter Power Spectrum ◽  
Non Linear ◽  
Standard Cosmological Model ◽  
Massive Neutrinos ◽  
On The Road

ABSTRACT We introduce an emulator approach to predict the non-linear matter power spectrum for broad classes of beyond-ΛCDM cosmologies, using only a suite of ΛCDM N-body simulations. By including a range of suitably modified initial conditions in the simulations, and rescaling the resulting emulator predictions with analytical ‘halo model reactions’, accurate non-linear matter power spectra for general extensions to the standard ΛCDM model can be calculated. We optimize the emulator design by substituting the simulation suite with non-linear predictions from the standard halofit tool. We review the performance of the emulator for artificially generated departures from the standard cosmology as well as for theoretically motivated models, such as f(R) gravity and massive neutrinos. For the majority of cosmologies we have tested, the emulator can reproduce the matter power spectrum with errors ${\lesssim}1{{\ \rm per\ cent}}$ deep into the highly non-linear regime. This work demonstrates that with a well-designed suite of ΛCDM simulations, extensions to the standard cosmological model can be tested in the non-linear regime without any reliance on expensive beyond-ΛCDM simulations.

Non-linear dynamic analysis of a flexible rotor supported by self-acting gas journal bearings

2004 ◽  
Vol 218 (12) ◽  
pp. 1527-1538 ◽  
Author(s):  
C-C Wang ◽  
M-J Jang ◽  
C-K Chen
Keyword(s):  
Reynolds Equation ◽  
Dynamic Behaviour ◽  
Rotational Velocity ◽  
Power Spectra ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Flexible Rotor ◽  
Non Linear ◽  
Subharmonic Response ◽  
Rotor Mass

This paper studies the bifurcation of a flexible rotor supported by gas film bearings. A time dependent mathematical model for gas journal bearings is presented. The finite difference method, with the successive overrelation method (SOR), is employed to solve the Reynolds equation. The system state trajectory, Poincare maps, power spectra and bifurcation diagrams are used to analyse the dynamic behaviour of the rotor and journal centre in the horizontal and vertical directions under different operating conditions. The analysis reveals a complex dynamic behaviour comprising periodic and subharmonic response of the rotor and journal centre. This paper shows how the dynamic behaviour of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the non-linear dynamics of gas film rotor-bearing systems.

Analysis of an aerodynamic grooved journal bearing with plain sleeve

2006 ◽  
Vol 220 (1) ◽  
pp. 51-60 ◽  
Author(s):  
C-C Wang
Keyword(s):  
Reynolds Equation ◽  
Dynamic Behaviour ◽  
Journal Bearing ◽  
Power Spectra ◽  
Operating Conditions ◽  
Complex Dynamic ◽  
Non Linear ◽  
Linear Behaviour ◽  
Bearing Number ◽  
Rotor Mass

This article studies the non-linear behaviour of a herringbone-grooved rigid rotor supported by a gas film bearing. A numerical method is employed to a time-dependent mathematical model for herringbone-grooved gas journal bearings. The finite difference method with successive over-relation method is employed to solve the Reynolds equation. The system state trajectory, Poincaré maps, power spectra, and bifurcation diagrams are used to analyse the dynamic behaviour of the rotor centre in the horizontal and vertical directions under different operating conditions. The analysis reveals a complex dynamic behaviour comprising periodic and quasi-periodic responses of the rotor centre. This article shows how the dynamic behaviour of this type of system varies with changes in rotor mass and bearing number. The results of this study contribute to a further understanding of the non-linear dynamics of aerodynamic-grooved journal bearing systems.

scholarly journals CMB and matter power spectra with non-linear dark-sector interactions

2017 ◽  
Vol 2017 (01) ◽  
pp. 050-050 ◽  
Author(s):  
R.F. vom Marttens ◽  
L. Casarini ◽  
W.S. Hipólito-Ricaldi ◽  
W. Zimdahl
Keyword(s):  
Power Spectra ◽  
Dark Sector ◽  
Non Linear

Random Wave Response of Double Pendulum Articulated Off-Shore Tower

2003 ◽  
Author(s):  
Nazrul Islam ◽  
Suhail Ahmad
Keyword(s):  
Equations Of Motion ◽  
Linear Equations ◽  
Time Integration ◽  
Power Spectra ◽  
Integration Scheme ◽  
Random Wave ◽  
Double Pendulum ◽  
Non Linear ◽  
Time Histories ◽  
Time Integration Scheme

Present study investigates the non-linear dynamic behavior of Double Hinged Articulated Tower (DHAT) under long crested random Sea and directional random sea. The non-linearities due to time wise variation of submergence, buoyancy, added mass, instantaneous tower orientation and resulting hydrodynamic loading have been taken into account for modeling the forcing functions of equation of motion which is derived by Largrangian approach. A long crested random sea has been modeled by Monte-Carlo Simulation using P-M spectrum. The non-linear equations of motion are solved by an iterative time integration scheme using Newmark’s β integration scheme. Various important parameters such as heel angles, deck displacements, base share for double hinged articulated tower under long and short crested random sea are compared and presented in the form of time-histories and their respective PSDFs. Statistical studies of random time histories have been carried out and important characteristics like mean, maxima, minima, standard deviations etc. have been analyzed. The dynamic behaviors have been investigated in detail in terms of various parametric combinations. Effect of current, and significant wave height are also studied. Sub and super harmonic excitations are highlighted through power spectra. A multi-hinged articulated tower is found to be economical and suitable for various offshore activities in adverse environmental and deep sea conditions.

scholarly journals Non-linear evolution of cosmological power spectra

1996 ◽  
Vol 280 (3) ◽  
pp. L19-L26 ◽  
Author(s):  
J. A. Peacock ◽  
S. J. Dodds
Keyword(s):  
Power Spectra ◽  
Linear Evolution ◽  
Non Linear
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