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Questions tagged [bao]

Baryon Acoustic Oscillations (BAO) are periodic density fluctuations in the density of matter in the universe. BAO is observed in the large-scale structure of the universe (e.g. distribution of clusters and quasars) in addition to the power spectrum of fluctuations in the Cosmic Microwave Background (CMB).

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What is the present day photon density, $\rho_{\gamma, 0}$?

I'm attempting to perform the integration that will yield the sound horizon at recombination: $$ c_s^2 = \frac{c^2}{3}\left[\frac{3}{4}\frac{\rho_{b,0}(1+z)^3}{\rho_{\gamma,0}(1+z)^4} + 1\right]^{-1}...
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BAO : Relation between redshift, Hubble constant and radial

From this link https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations#Measured_observables_of_dark_energy , I can't get this relation : $$c\Delta z = H(z)\Delta \chi\quad\quad(1)$$ with $z$ ...
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BAO : Relation between redshift, Hubble constant and radial coordinate

From this wikipedia link relation about BAO, I can't get this relation : $$c\Delta z = H(z)\Delta \chi\quad\quad(1)$$ with $z$ redshift, $H(z)$ Hubble constant at redshift = $z$ and $\chi$ radial ...
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What causes structure formation: Baryon acoustic oscillations or inflation?

Formation of structures such as galaxies and galaxy clusters require anisotropies in the cosmic plasma which (as I understand) were due to the anisotropies or density inhomogeneities created by Baryon ...
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Is the baryonic acoustic oscillation a sound wave?

I was told by a friend that a baryon acoustic oscillations are sound waves with a wavelength so large that they can travel through a vacuum. Is there any truth to this? I read what Wikipedia has to ...
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Different cold dark matter density parameters from early- and late-Universe observations

Edit: @John Rennie, thank you for your good and concise review of how the parameters of the $\Lambda$CDM model evolve with time. However, the answer I was looking for was a different one (sorry for ...
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Is BAO a standing or moving wave?

The sound horizon is the distance that a wave of plasma can move from the end of Inflation to Recombination (roughly 300,000 years). In several papers and talks, this is described as a moving wave (...
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Are there any public program that can calculate baryon acoustic oscillations (BAO) acoustic peak from the data Lyman alpha spectra of BOSS?

Are there any public program that can calculate baryon acoustic oscillations (BAO) acoustic peak from the data Lyman alpha spectra of Baryon Oscillation Spectroscopic Survey (BOSS)? I am confused in ...
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Baryon Acoustic oscillations - simple confusion about length scales

I am confused about length scales and baryon acoustic oscillations. I am clearly missing something very simple. The length scale found in the $SDSS$ and $2dF$ data is quoted as being $150Mpc$. ...
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What determines the size of features on the CMB?

I have been learning about baryon acoustic oscillations. I am however confused about the size of the features as seen on the CMB. It is claimed that the largest structures have a size given by the ...
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baryon acoustic oscillation

I have one question about baryon acoustic oscillation. I understand why we should have the baryon-photon fluid sound wave before recombination: Suppose we have a spherical overdense region. This ...
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Galaxy bias and baryon acoustic oscillations (BAO)

I have a doubt with the concept of galaxy bias and how it affects baryon acoustic oscillations, it is supposed to mean that by measuring the distribution of galaxies we are not measuring the actual ...
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Why is the Baryon Acoustic Oscillations (BAO) calculated like this?

In the Wikipedia, it says that, when calculating the Baryon Acoustic Oscillations (sound horizon), we measure $150\text{ Mpc}$, saying that the sound horizon is the "Physical Length of sound horizon ...
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Connection between BAO und CMB Spectrum

I have a problem understanding the connection between the accoustic peaks in the CMB spectrum and the baryon oscillation picture. On the one hand it is stated, that the odd accoustic peaks (1,3,5..) ...