Big-bang nucleosynthesis and the baryon density of the universe

The abundance of 4He restricts the number of independent lepton families to three or possibly four. Building Blocks of Matter: Most lithium and beryllium is produced by cosmic ray collisions breaking up some of the carbon produced in stars.

Big Bang nucleosynthesis

Understanding this earliest of eras in the history of the universe is currently one of the greatest unsolved problems in physics. As noted above, in the standard picture of BBN, all of the light element abundances depend on the amount of ordinary matter baryons relative to radiation photons.

And a new measurement of the free neutron lifetime is 6 sigma smaller that the previous world average, giving a new prediction of the helium abundance of He did not grasp the cosmological implications of this fact, and indeed at the time it was highly controversial whether or not these nebulae were "island universes" outside our Milky Way.

Lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei. Apparently a new unified theory of quantum gravitation is needed to break this barrier. Lithium Lithium-7 and lithium-6 produced in the Big Bang are in the order of: If the redshift is interpreted as a Doppler shift, the recessional velocity of the object can be calculated.

The cosmological principle states that on large scales the universe is homogeneous and isotropic. These pieces of additional physics include relaxing or removing the assumption of homogeneity, or inserting new particles such as massive neutrinos. Because of the free expansion character of the early evolution of the universe, a larger number of neutrino types increases the rate at which the universe expands and reduces the time available for element building.

The first, which is largely of historical interest, is to resolve inconsistencies between BBN predictions and observations.

Thanks to the pioneering efforts of George Gamow and his collaborators, there now exists a satisfactory theory as to the production of light elements in the early Universe. The weakly interacting particles are known as leptons and include the electrons, muons, tau particles, and their associated neutrinos.

At high density and temperature, the universe is filled with particles of many unfamiliar types. A very few helium nuclei combine into heavier nuclei giving a small abundance of Li7 coming from the Big Bang. Eventually the temperature gets so low that the electrostatic repulsion of the deuterons causes the reaction to stop.

It seems like we really understand the physical processes which went on in the first few minutes of the evolution of the Universe! The observed lithium abundance in stars is less than the predicted lithium abundance, by a factor of about 2. Distance measures cosmology and Scale factor universe Observations of distant galaxies and quasars show that these objects are redshifted—the light emitted from them has been shifted to longer wavelengths.

If the expansion of the universe continues to acceleratethere is a future horizon as well. The input parameters to the model calculation include the density of baryons relative to the cosmic background radiation, the number of neutrino families, and a set of nuclear reaction rates derived from laboratory observations.

There has been a dispute about the actual primordial helium abundance in the Universe: There are no known post-Big Bang processes which can produce significant amounts of deuterium. The half-life of the neutron is seconds.


In order to build up multiple baryon isotopes, pairs of the individual baryons must combine. But stars destroy lithium so it is hard to assess the significance of this difference. Quantifying the evolution of the universe from this early time until the present is a central goal of modern cosmology.

The strongly interacting particles are composed of two or three quarks and are known as hadrons. So far combinations beyond weak forces and electromagnetic fields are only a goal of particle physics and cosmology.

Light elements namely deuterium, helium, and lithium were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe.

Ulrich Pick a style below, and copy the text for your bibliography.Big-bang nucleosynthesis plays a crucial role in constraining big-bang cosmology. Although the uncertainties in the observations of the light elements are governed by systematic effects, firm bounds on the density of baryons in the Universe can be set.

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 x 10() and x 10() grams per cubic centimeter (corresponding to about 1 to 15 percent of the critical density)., big bang online software system. This site hosts an online Big Bang Nucleosynthesis code and provides extensive resources for studies of the Big Bang.

and compare the results to observations of the primordial light element abundances to constrain the baryon density. Monte Carlo simulations can also be run wherein.

A few minutes into the expansion, when the temperature was about a billion (one thousand million) kelvin and the density was about that of air, neutrons combined with protons to form the universe's deuterium and helium nuclei in. Using the baryon density predicted by big bang nucleosynthesis, the total mass of the universe would have been 25% helium, % deuterium and even less than that would have been lithium.

During the s, there was a major puzzle in that the density of baryons as calculated by Big Bang nucleosynthesis was much less than the observed mass of the universe based on measurements of galaxy rotation curves and galaxy cluster dynamics.

Big-bang nucleosynthesis and the baryon density of the universe
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