OU-TAP-13 To appear in Prog.Theor.Phys.vol.94(1995) Analysis of Non-Linear Mode Coupling of Cosmological Density Fluctuations by the Pseudo-Spectral Method
نویسنده
چکیده
The pseudo-spectral method is proposed for following the evolution of density and velocity uctuations at the weakly non-linear stage in the expanding universe with a good accuracy. In this method, the evolution of density and velocity uctuations is integrated in the Fourier Space with using FFT. This method is very useful to investigate accurately the non-linear dynamics in the weakly non-linear regime. Because the pseudo-spectral method works directly in the Fourier space, it should be especially useful for examining behavior in the Fourier domain, for an example, the e ects of the non-linear coupling of di erent wave modes on the evolution of the power spectrum. I show the results of this analysis both in one and three dimensional systems.
منابع مشابه
Nonlinear Effects Due to the Coupling of Long-wave Modes
The cosmological fluid equations are used to study the nonlinear mode coupling of density fluctuations. We find that for realistic cosmological spectra there is a significant contribution to the nonlinear evolution on scales of interest to large-scale structure from the long-wave part of the initial spectrum. A consequence of this mode coupling is that at high redshift, z, the nonlinear scale [...
متن کاملReturn mapping of phases and the analysis of the gravitational clustering hierarchy
In the standard paradigm for cosmological structure formation, clustering develops from initially random-phase (Gaussian) density fluctuations in the early Universe by a process of gravitational instability. The later, non-linear stages of this process involve Fourier mode-mode interactions that result in a complex pattern of non-random phases. We present a novel mapping technique that reveals ...
متن کاملOptimal control of switched systems by a modified pseudo spectral method
In the present paper, we develop a modified pseudospectral scheme for solving an optimal control problem which is governed by a switched dynamical system. Many real-world processes such as chemical processes, automotive systems and manufacturing processes can be modeled as such systems. For this purpose, we replace the problem with an alternative optimal control problem in which the switching t...
متن کاملLeast Squares Techniques for Extracting Water Level Fluctuations in the Persian Gulf and Oman Sea
Extracting the main cyclic fluctuations from sea level changes of the Persian Gulf and Oman Sea is vital for understanding the behavior of tides and isolating non-tidal impacts such as those related to climate and changes in the ocean-sea circulations. This study compares two spectral analysis methods including: Least Squares Spectral Analysis (LSSA) and Least Squares Harmonic Estimation (LSHE)...
متن کاملNon-linearity and Non-Gaussianity through Phase Information
In the standard picture of structure formation, initially random-phase fluctuations are amplified by non-linear gravitational instability to produce a final distribution of mass which is highly non-Gaussian and has highly coupled Fourier phases. Second-order statistics, such as the power spectrum, are blind to this kind of phase association. We discuss the information contained in the phases of...
متن کامل