Big-Bang Nucleosynthesis and the Baryon Density of the Universe

Copi, Craig J.; Schramm, David N.; Turner, Michael S.

doi:10.1126/science.7809624

Cited by 389 publications

(391 citation statements)

References 79 publications

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“…At high Ω B , this reflects the reduced rate of d(p, γ) 3 He indicated by recent improved measurements. These effects cancel in the middle of the Copi et al [1] concordance interval, so that the disagreement with SKM is not serious in the likely range for Ω B . Since much of the post-big-bang evolution of D/H and 3 He/H is expected to consist of the burning of deuterium into 3 He, the sum of these two number densities is often considered in comparing them to the BBN predictions.…”

Section: Resultsmentioning

confidence: 99%

“…Some subsequent calculations have incorporated the reaction rate derived from that measurement by its authors (e.g., Copi et al [1]), using as the uncertainty the 6% uncertainty in the experiment's cross section normalization. Krauss and Romanelli [10] pointed out that it is not always the best policy to base calculations on only the most recent measurement, and we agree.…”

Section: T(α γ) 7 LImentioning

confidence: 99%

“…Some subsequent BBN calculations (e.g., Ref. [1]) have incorporated the latest measurement of t(α, γ) 7 Li [14] by replacing the SKM fit with a reaction rate and uncertainty based on that measurement alone. These numbers have not found their way into all subsequent work (e.g., Ref.…”

Section: A the Databasementioning

confidence: 99%

“…The success of big-bang nucleosynthesis theory is indicated by the narrow range of cosmic baryon density over which the observed abundances of the light isotopes, D, 3 He, 4 He, and 7 Li agree with their calculated abundances. This narrow range in the theory's single free parameter (once the input physics is specified) was summarized in 1995, in units of critical density, as Ω B h 2 = .009-.020 [1]. (h is the Hubble constant in units of 100 km/s/Mpc; this limit is also customarily quoted in terms of the baryon-to-photon number ratio, 2.5 × 10 −10 < η < 6 × 10 −10 .…”

Section: Introductionmentioning

confidence: 99%

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Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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We present a Monte Carlo method for direct incorporation of nuclear inputs in primordial nucleosynthesis calculations. This method is intended to remedy shortcomings of current error estimation, by eliminating intermediate data evaluations and working directly with experimental data, allowing error estimation based solely on published experimental uncertainties. This technique also allows simple incorporation of new data and reduction of errors with the introduction of more precise data. Application of our method indicates that previous error estimates on the calculated abundances were too large by as much as a factor of three. Since uncertainties in the BBN calculation currently dominate inferences drawn from light-element abundances, the re-estimated errors have important consequences for cosmic baryon density, neutrino physics, and lithium depletion in halo stars. Our direct method allows detailed discussion of the status of the nuclear inputs, by identifying clearly the places where improved cross section measurements would be most useful. 26.35.+c, 98.80.Ft

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Section: Resultsmentioning

confidence: 99%

Section: T(α γ) 7 LImentioning

confidence: 99%

Section: A the Databasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating reaction rates and uncertainties for primordial nucleosynthesis

2000

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“…From the photoionization model, this corresponds to a neutral hydrogen fraction of H I/H ≈ 10 −2.3±0. 5 . The abundances of the two components, given in the Table, are both low and they differ.…”

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confidence: 99%

Cosmological baryon density derived from the deuterium abundance at redshift z = 3.57

Tytler

Fan

Burles

1996

Nature

305

281

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The primordial ratio of the number of deuterium to hydrogen nuclei (D/H) created in big bang nucleosynthesis is the most sensitive measure of the cosmological baryon to photon ratio and the cosmological density of baryons Ω b (1-5). In the interstellar medium (ISM) of our Galaxy D/H = 1.6 ± 0.1 × 10 −5 (6), which places a strict lower limit on the primordial abundance, because stars reduce the proportion of D in the ISM. Quasar absorption systems (QAS) should give definitive measurements of the primordial D because they can sample metal-poor gas at early epochs where the destruction of D should be negligible. A probable measurement of a high abundance ratio was reported in one QAS: D/H ≈ 24 × 10 −5 (7,8). Here we report a measurement of low D/H = 2.3 ×10 −5 , in another QAS, which is consistent with D/H in the ISM, with models of Galactic chemical evolution, (9,10), and with earlier data (7,8) provided that D line is strongly contaminated. We have internal consistency checks, and believe that this is the first direct measurement of a primordial abundance ratio. It provides the most accurate measurement of the baryon density: a high value of Ω b = 0.05, assuming a Hubble constant H 0 = 70 km s −1 Mpc −1 .Deuterium is rarely seen in QAS because the associated hydrogen is usually distributed over a wide range of velocities and its absorption covers deuterium. We selected QSO 1937-1009 because we found that the absorption system at z = 3.572 showed unusually weak metal lines in low resolution spectra, which we took to indicate that the gas was distributed in one or two narrow velocity components (11). We obtained optical spectra of QSO 1937-1009 (z em = 3.78, V ≃ 17.5) with the HIRES echelle spectrograph (12) on the W. M. Keck 10-m telescope. The high quality spectra make this amongst the best characterized QAS, and show strong absorption at the expected position of the D Lyα line and weak but highly significant absorption at D Lyβ .The weak metal lines in the system, C II, C IV, Si II, and Si IV, appear to have the same profiles, which are adequately described by two components separated by 15 km s −1 .

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The first second of the Universe

2003

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The history of the Universe after its first second is now tested by high quality observations of light element abundances and temperature anisotropies of the cosmic microwave background. The epoch of the first second itself has not been tested directly yet; however, it is constrained by experiments at particle and heavy ion accelerators. Here I attempt to describe the epoch between the electroweak transition and the primordial nucleosynthesis. The most dramatic event in that era is the quark--hadron transition at 10 $\mu$s. Quarks and gluons condense to form a gas of nucleons and light mesons, the latter decay subsequently. At the end of the first second, neutrinos and neutrons decouple from the radiation fluid. The quark--hadron transition and dissipative processes during the first second prepare the initial conditions for the synthesis of the first nuclei. As for the cold dark matter (CDM), WIMPs (weakly interacting massive particles) -- the most popular candidates for the CDM -- decouple from the presently known forms of matter, chemically (freeze-out) at 10 ns and kinetically at 1 ms. The chemical decoupling fixes their present abundances and dissipative processes during and after thermal decoupling set the scale for the very first WIMP clouds.Comment: review to appear in Annalen der Physik (51 pages, 16 figures); references added (v2); typos corrected, resembles published version (v3

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Big-Bang Nucleosynthesis and the Baryon Density of the Universe

Cited by 389 publications

References 79 publications

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Estimating reaction rates and uncertainties for primordial nucleosynthesis

Cosmological baryon density derived from the deuterium abundance at redshift z = 3.57

The first second of the Universe

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