Big-Bang nucleosynthesis: Constraints on nuclear reaction rates, neutrino degeneracy, inhomogeneous and Brans–Dicke models

Nakamura, Riou; Hashimoto, Minoru; Ichimasa, Ryotaro; Arai, K.

doi:10.1142/s0218301317410038

Cited by 22 publications

(21 citation statements)

References 90 publications

(108 reference statements)

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“…The obvious generalization of this work would be a reconsideration of fluctuations on smaller scales, where differential neutron and proton diffusion becomes important [16][17][18][19]. Such models, however, are considerably more complex, since the geometry and magnitude of the fluctuations both have a strong influence on the final results.…”

Section: Discussionmentioning

confidence: 99%

Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology

Barrow

Scherrer

2018

Phys. Rev. D

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We reexamine big bang nucleosynthesis with large-scale baryon density inhomogeneities when the length scale of the density fluctuations exceeds the neutron diffusion length (∼ 10 7 −10 8 cm at BBN), and the amplitude of the fluctuations is sufficiently small to prevent gravitational collapse. In this limit, the final light element abundances can be determined by simply mixing the abundances from regions with different baryon/photon ratios without interactions. We examine gaussian, lognormal, and gamma distributions for the baryon/photon ratio, η. We find that the deuterium and lithium-7 abundances increase with the RMS fluctuation in η, while the effect on helium-4 is much smaller. We show that these increases in the deuterium and lithium-7 abundances are a consequence of Jensen's inequality, and we derive analytic approximations for these abundances in the limit of small RMS fluctuations. Observational upper limits on the primordial deuterium abundance constrain the RMS fluctuation in η to be less than 17% of the mean value of η. This provides us with a new limit on the graininess of the early universe.

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Section: Discussionmentioning

confidence: 99%

Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology

Barrow

Scherrer

2018

Phys. Rev. D

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“…[5,6,12,13,14] See however [12] for suggestions on new reaction rates that may influence BBN. Also, in Nakamura et al [13] the broad range of reactions that can enter into the inhomogeneous big bang is summarized. In order to be useful as a cosmological constraint one must know relevant nuclear reaction rates to very high precision (∼ 1%).…”

Section: Physics Of Bbnmentioning

confidence: 99%

Big bang nucleosynthesis, the CMB, and the origin of matter and space-time

Mathews

Gangopadhyay

Sasankan

et al. 2018

AIP Conference Proceedings

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We summarize some applications of big bang nucleosythesis (BBN) and the cosmic microwave background (CMB) to constrain the first moments of the creation of matter in the universe. We review the basic elements of BBN and how it constraints physics of the radiation-dominated epoch. In particular, how the existence of higher dimensions impacts the cosmic expansion through the projection of curvature from the higher dimension in the "dark radiation" term. We summarize current constraints from BBN and the CMB on this brane-world dark radiation term. At the same time, the existence of extra dimensions during the earlier inflation impacts the tensor to scalar ratio and the running spectral index as measured in the CMB. We summarize how the constraints on inflation shift when embedded in higher dimensions. Finally, one expects that the universe was born out of a complicated multiverse landscape near the Planck time. In these moments the energy scale of superstrings was obtainable during the early moments of chaotic inflation. We summarize the quest for cosmological evidence of the birth of space-time out of the string theory landscape. We will explore the possibility that a superstring excitations may have made itself known via a coupling to the field of inflation. This may have left an imprint of "dips" in the power spectrum of temperature fluctuations in the cosmic microwave background. The identification of this particle as a superstring is possible because there may be evidence for different oscillator states of the same superstring that appear on different scales on the sky. It will be shown that from this imprint one can deduce the mass, number of oscillations, and coupling constant for the superstring. Although the evidence is marginal, this may constitute the first observation of a superstring in Nature.

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“…Fortunately, unlike in stars, the energies at which these reactions occur in the early universe are directly accessible in laboratory experiments. Although considerable progress has been made [6,[12][13][14][15][16] toward quantifying and reducing uncertainties in the relevant rates, improved reaction rates are still needed for the neutron life time [17,18], the 2 H(p, γ) 3 He, 2 H(d, n) 3 He, 3 He(d, p) 3 He, 3 He(α, γ) 7 Be, and 7 Be(n, α) 4 He reactions.…”

Section: Elementary Dynamics Of Space-timementioning

confidence: 99%

“…A number of recent papers have addressed this problem [13,14,[25][26][27][28]. At present it is not yet known if this discrepancy derives from a destruction of Lithium on the old stars used to deduce the primordial Lithium abundance, or if it requires exotic new physics in the early universe [13,14,[25][26][27], or even a modification of the particle statistics in BBN itself [28]. For the remainder of this introduction we will adopt the premise that this disagreement may indicate new physics in the early universe.…”

Section: Comparison Of Bbn With Observed Abundancesmentioning

confidence: 99%

Primordial Nucleosynthesis: Constraints on the Birth of the Universe

et al. 2018

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We review the basic elements of big bang nucleosythesis (BBN) and how a comparison of predicted light-element abundances with observations constrains physics of the radiation-dominated epoch. We then summarize some applications of BBN and the cosmic microwave background (CMB) to constrain the first moments of the birth of the universe. In particular, we discuss how the existence of higher dimensions impacts the cosmic expansion through the projection of curvature from the higher dimension in the "dark radiation" term. We summarize current constraints from BBN and the CMB on this brane-world dark radiation term. At the same time, the existence of extra dimensions during the earlier inflation impacts the tensor to scalar ratio and the running spectral index as measured in the CMB. We summarize how the constraints on inflation shift when embedded in higher dimensions. Finally, one expects that the universe was born out of a complicated multiverse landscape near the Planck time. In these moments the energy scale of superstrings was obtainable during the early moments of chaotic inflation. We summarize the quest for cosmological evidence of the birth of space-time out of the string theory landscape. We will explore the possibility that a superstring excitations may have made itself known via a coupling to the field of inflation. This may have left an imprint of "dips" in the power spectrum of temperature fluctuations in the cosmic microwave background. The identification of this particle as a superstring is possible because there may be evidence for different oscillator states of the same superstring that appear on different scales on the sky. It will be shown that from this imprint one can deduce the mass, number of oscillations, and coupling constant for the superstring. Although the evidence is marginal, this may constitute the first observation of a superstring in Nature.

show abstract

Big-Bang nucleosynthesis: Constraints on nuclear reaction rates, neutrino degeneracy, inhomogeneous and Brans–Dicke models

Cited by 22 publications

References 90 publications

Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology

Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology

Big bang nucleosynthesis, the CMB, and the origin of matter and space-time

Primordial Nucleosynthesis: Constraints on the Birth of the Universe

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