Understanding Coherent Large Scale Modes in Power Spectra

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    Coherent Modes
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Discussion Overview

The discussion revolves around the concept of "coherent large scale modes" in the context of power spectra, specifically in relation to Fourier space and wavenumber. Participants seek clarification on the terminology and its implications within the framework of a note they are reviewing.

Discussion Character

  • Exploratory
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the meaning of "coherent large scale modes" as presented in a power spectrum plot, specifically asking if "mode" refers to wavenumber.
  • Another participant requests a citation for the source material to provide context for the discussion.
  • A participant expresses uncertainty about the definition of "mode" in the context of power spectra and seeks clarification on the term "coherent mode."
  • It is noted that Fourier modes are related to time-dependent functions in the Fourier decomposition, indexed by comoving wavenumber, k, which describe the time evolution of perturbations on that scale.

Areas of Agreement / Disagreement

The discussion does not reach a consensus, as participants are still seeking definitions and clarifications regarding the terms used in the context of power spectra.

Contextual Notes

Participants have not provided specific definitions or examples from the source material, which may limit the clarity of the discussion. There is also a lack of consensus on the terminology and its implications.

shirin
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Hi everyone,
I am reading a paper, which discusses about power spectrum. There is a plot which is power versus k(wave number). It says something about "coherent large scale modes". Would you please tell me what the meaning of this is?
 
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Cite the paper instead of a pinada
 
Sorry, I shouldn't have said "a paper". It is a note. I don't know what mode is in regard to power spectrum in Fourier space? Does it mean wavenumber? And in addition what "coherent mode" is?
 
Again, can you cite the paper you are reading? Perhaps even give us a link to it?
 
shirin said:
Sorry, I shouldn't have said "a paper". It is a note. I don't know what mode is in regard to power spectrum in Fourier space? Does it mean wavenumber? And in addition what "coherent mode" is?
They are Fourier modes, which are the time-dependent functions in front of the plane wave basis states in the Fourier decomposition of a function. The mode functions are indexed by comoving wavenumber, k: they describe the time evolution of perturbations on the scale k.
 

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