Steigman, Zeller & Zentner: (2002) employed SNIa data and the assumption of ΛCDM to obtain Ωm, and then computed the baryon density by combining Ωm with an estimate of the baryon fraction fb derived from X-ray observations of clusters of galaxies (e.g. Ωb = fb Ωm)..
What is baryonic matter in cosmology?
Astronomers therefore use the term 'baryonic' to refer to all objects made of normal atomic matter, essentially ignoring the presence of electrons which, after all, represent only ~0.0005 of the mass. Neutrinos, on the other hand, are (correctly) considered non-baryonic by astronomers..
The agreement between the predicted and observed abundances of deuterium, helium-3, helium-4, and lithium-7 confirms the standard cosmology model and allows accurate determination of the baryon density, between 1.7 × 10-31 and 4.1 × 10-31 grams per cubic centimeter (corresponding to about 1 to 15 percent of the
Does the universe have a positive baryon number density?
The universe, as a whole, seems to have a nonzero positive baryon number density. Since it is assumed in cosmology that the particles we see were created using the same physics we measure today, it would normally be expected that the overall baryon number should be zero, as matter and antimatter should have been created in equal amounts.
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What are baryon acoustic oscillations?
In cosmology, baryon acoustic oscillations ( BAO) are fluctuations in the density of the visible baryonic matter (normal matter) of the universe, caused by acoustic density waves in the primordial plasma of the early universe.
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What is baryogenesis in cosmology?
In physical cosmology, baryogenesis (also known as baryosynthesis ) is the physical process that is hypothesized to have taken place during the early universe to produce baryonic asymmetry, i.e. the imbalance of matter ( baryons) and antimatter (antibaryons) in the observed universe.
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What is the CDM model of baryon density?
According to the Λ CDM model, the baryon density can only vary as a result of the expansion of the Universe, so that its present-day value inferred from either the CMB or BBN should be the same.
Fluctuations in the density of the normal matter of the universe
In cosmology, baryon acoustic oscillations (BAO) are fluctuations in the density of the visible baryonic matter of the universe, caused by acoustic density waves in the primordial plasma of the early universe. In the same way that supernovae provide a standard candle for astronomical observations, BAO matter clustering provides a standard ruler for length scale in cosmology. The length of this standard ruler is given by the maximum distance the acoustic waves could travel in the primordial plasma before the plasma cooled to the point where it became neutral atoms, which stopped the expansion of the plasma density waves, freezing them into place. The length of this standard ruler can be measured by looking at the large scale structure of matter using astronomical surveys. BAO measurements help cosmologists understand more about the nature of dark energy by constraining cosmological parameters.
Cosmology baryon density
Imbalance of matter and antimatter in the observable universe
In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, is the observed imbalance in baryonic matter and antibaryonic matter in the observable universe. Neither the standard model of particle physics nor the theory of general relativity provides a known explanation for why this should be so, and it is a natural assumption that the universe is neutral with all conserved charges. The Big Bang should have produced equal amounts of matter and antimatter. Since this does not seem to have been the case, it is likely some physical laws must have acted differently or did not exist for matter and antimatter. Several competing hypotheses exist to explain the imbalance of matter and antimatter that resulted in baryogenesis. However, there is as of yet no consensus theory to explain the phenomenon, which has been described as one of the great mysteries in physics.
In cosmology, the missing baryon problem is an observed discrepancy between the amount of baryonic matter detected from shortly after the Big Bang and from more recent epochs. Observations of the cosmic microwave background and Big Bang nucleosynthesis studies have set constraints on the abundance of baryons in the early universe, finding that baryonic matter accounts for approximately 4.8% of the energy contents of the Universe. At the same time, a census of baryons in the recent observable universe has found that observed baryonic matter accounts for less than half of that amount. This discrepancy is commonly known as the missing baryon problem. The missing baryon problem is different from the dark matter problem, which is non-baryonic in nature.
