Showing papers on "Big Bang nucleosynthesis published in 1992"
TL;DR: In this paper, the authors estimate the baryon mass density of the universe due to the stars in galaxies and the hot gas in clusters and groups of galaxies using the Efstathiou, Ellis & Peterson luminosity function, together with van der Marel and Persic & Salucci's mass-to-light versus luminosity relationships.
Abstract: We estimate the baryon mass density of the Universe due to the stars in galaxies and the hot gas in clusters and groups of galaxies. The galaxy contribution is computed by using the Efstathiou, Ellis & Peterson luminosity function, together with van der Marel and Persic & Salucci’s mass-to-light versus luminosity relationships. We find stars ≃ 0.002. For clusters and groups we use the Edge et al. X -ray luminosity function, and Edge & Stewart and Kriss, Cioffi & Canizares’ (gas mass )-luminosity relations. We find gas ≃ 0.001. The total amount of visible baryons is then b ≃ 0.003, i.e. less than 10 per cent of the lower limit predicted by standard primordial nucleosynthesis, implying that the great majority of baryons in the Universe are unseen.
247 citations
TL;DR: The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed and constraints to {mu} which are more restrictive than any previous limit are found.
Abstract: The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed. The computation consists of a numerical integration of the Friedmann-Robertson-Walker Einstein equations which describe a universe containing radiation, dust, and a one-scale''-model cosmic-string component. The procedure takes into account the effects of the annihilations of massive particle species on the equation of state of the cosmological fluid. An expression for the power emitted per mode of oscillation by a cosmic-string loop, suggested by both analytic calculations and recent numerical simulations, is used. The results of the computation are spectra of the cosmic-string gravitational radiation at nucleosynthesis and at present. Comparison of these spectra with the observed bounds on pulsar timing noise, and the observed bound on the effective number of light neutrino species permitted by the model of nucleosynthesis, allows one to exclude a range of values of {mu}, the cosmic-string linear mass density, for certain values of {alpha}, the size of a newly formed loop as a fraction of the particle horizon radius. We find constraints to {mu} which are more restrictive than any previous limit.
179 citations
TL;DR: In this paper, the cosmological consequences of neutrino degeneracy are explored with particular attention to the effects on primordial nucleosynthesis, and a combination of bounds from DBBN and the density and expansion rate of the Universe constraints the e-neutrino deformation (−0.06 ⪅ξe⪅1.1), the μ, τ-NE, τ−6.9) and, the nucleon-to-photon rati0 (2.8⫅η10−19).
131 citations
TL;DR: In this article, the authors studied new physical phenomena and constraints in generalized scalar-tensor theories of gravity with Phi-dependent masses and found an entropy increase effect during the matter era and, in principle, a measurable effect on the motion of the halo of spiral galaxies.
Abstract: The authors study new physical phenomena and constraints in generalized scalar-tensor theories of gravity with Phi -dependent masses. They investigate a scenario (which can arise in string theories) with two types of Phi -dependent masses which could correspond to visible and dark matter sectors. The parameters of this theory are constrained from post-Newtonian bounds, primordial nucleosynthesis and the age of the universe. They present a perfect fluid formalism for the dark matter sector with variable masses and find an entropy increase effect during the matter era and, in principle, a measurable effect on the motion of the halo of spiral galaxies. For the case of string effective theories, the constancy of gauge couplings provides new bounds which are orders of magnitude stronger than the previous ones.
100 citations
TL;DR: In this paper, the primordial beryllium abundance in the early universe has been investigated in terms of the evolution of galactic chemical evolution, using observations of nine very metal-poor stars.
Abstract: Standard Big Bang nucleosynthesis predicts a very small primordial abundance of beryllium. Observations of nine very metal-poor stars indicate a beryllium abundance roughly proportional to the oxygen abundance, a trend that can be explained in terms of galactic chemical evolution. Combining this rate of beryllium production with recent observations of boron and lithium in similar stars yields an upper limit to the primordial beryllium abundance several orders of magnitude greater than the cosmological prediction, a result that can be explained by cosmicray activity in the early Galaxy.
94 citations
TL;DR: In this paper, a study on the lithium abundance in 36 T Tauri stars (mass range 0.4-2.25 M ⊙ ), partly based on high-dispersion spectra taken with the Isaac Newton Telescope, is presented.
Abstract: A study on the lithium abundance in 36 T Tauri stars (mass range 0.4-2.25 M ⊙ ), partly based on high-dispersion spectra taken with the Isaac Newton Telescope, is presented. Veiling effects have been taken into account when measuring the Li I λ670.8 nm doublet equivalent width. Non-LTE effects, studied in the range 4000 ≤ T eff ≤ 5000 K, are significant for the coolest atmospheres, becoming smaller for T eff close to 5000 K. The non-LTE corrections tend to increase the derived abundance, except for high temperatures (∼ 5000 K) and log N(Li) ≥ 3, where an inverse trend is found. The majority of the stars in the sample present a rather narrow distribution of abundance around log N(Li) = 3.2, the expected value of the present cosmic lithium abundance. These results do not provide support to models of inhomogeneous big bang nucleosynthesis, that predict a very high value for the primordial lithium abudance
80 citations
TL;DR: In this paper, the abundances of three halo stars and an upper limit for a fourth were derived considering models for Galactic and primordial synthesis of Be, using constraints imposed by its overall metallicity distribution.
Abstract: We have used a spectrum synthesis code to measure Be abundances for three halo stars and an upper limit for a fourth. The abundances are discussed considering models for Galactic and primordial synthesis of Be. Computations for inhomogeneous big bang models range over two orders of magnitude, and we can at best place upper limits on possible primordial nucleosynthesis. We compute a new model for the evolution of Be abundances in the halo, using constraints imposed by its overall metallicity distribution. Observations of stars of [Fe/H]∼−2.0 are required to clarify the enrichment history of this element
75 citations
TL;DR: In this article, the primordial abundances of deuterium and 3 He provided a valuable probe of cosmology and a crucial test of the consistency of big bang nucleosynthesis (BBN).
Abstract: The primordial (i.e., pre-Galactic) abundances of deuterium and of 3 He provide a valuable probe of cosmology and a crucial test of the consistency of big bang nucleosynthesis (BBN). To utilize current observational data on the D and 3 He abundances in the solar system and the interstellar medium to infer the primordial values, it is necessary to adopt some-necessarily model-dependent-assumptions about the evolution of D and 3 He during the course of Galactic evolution. Here, we follow the D and 3 He evolution using several models for the chemical evolution of the disk of the Galaxy
60 citations
01 Jan 1992
TL;DR: A guide to its use is presented, followed by a series of appendices containing specific details such as a summary of the basic structure of the program, a description of the computational algorithm, and a presentation of the theory incorporated into the program.
Abstract: This is a revised description and manual for the primordial nucleosynthesis program, NUC123, an updated and modified version of the code of R.V. Wagoner. NUC123 has undergone a number of changes, further enhancing its documentation and ease of use. Presented here is a guide to its use, followed by a series of appendices containing specific details such as a summary of the basic structure of the program, a description of the computational algorithm, and a presentation of the theory incorporated into the program.
59 citations
TL;DR: In this paper, a consistency check on the combination of big bang nucleosynthesis and GCR spallation was performed on the Be and B data from a sample of hot population II stars.
Abstract: The astrophysical Li-7 abundance is considered to be largely primordial, while the Be and B abundances are thought to be due to galactic cosmic ray (GCR) spallation reactions on top of a much smaller big bang component. But GCR spallation should also produce Li-7. As a consistency check on the combination of big bang nucleosynthesis and GCR spallation, the Be and B data from a sample of hot population II stars is used to subtract from the measured Li-7 abundance an estimate of the amount generated by GCR spallation for each star in the sample, and then to add to this baseline an estimate of the metallicity-dependent augmentation of Li-7 due to spallation. The singly reduced primordial Li-7 abundance is still consistent with big bang nucleosynthesis, and a single GCR spallation model can fit the Be, B, and corrected Li-7 abundances for all the stars in the sample.
48 citations
TL;DR: In this article, a thorough calculation of light-element production in Brans-Dicke cosmologies is presented, by taking into account the most general class of these models.
Abstract: A thorough calculation of light-element production in Brans-Dicke cosmologies is presented, by taking into account the most general class of these models. The comparison of the outputs of our calculation with current observational data results in bounds on the allowed ω-values. It is found that cosmological models where (dφ/dt) R 3 → C ¬=; 0 when R → 0 and high values of the expansion rate of the universe are ruled out by the primordial nucleosynthesis test. However, if C = 0, light-element production imposes less restrictive bounds on the parameter ω than the experiments in the weak field limit
TL;DR: In this paper, the authors examined the consequences for primordial nucleosynthesis of a weakly interacting neutrino which possesses both Dirac and Majorana mass terms, and showed that δm p-D | −10 eV is tight even in the special case of a pseudo-Dirac Neutrino.
TL;DR: The erects are generic to early-Universe decay of fermions, not just of relevance for 17 keV neutrinos, and can form a Bose condensate, with interesting consequences for galaxy formation and the dark-matter problem.
Abstract: Early-Universe decay of 17 keV neutrinos is likely to happen in equilibrium for lifetime t free <10 5 sec. For 3×10 -4
TL;DR: In this article, the primordial abundance of anomalous 5 Li which contains three protons in the lowest level was estimated and an upper limit for the probability of having two pairs in a symmetric state with respect to exchange was obtained, corresponding to a small violation of the Pauli exclusion principle.
TL;DR: In this paper, it was shown that the degree of supercooling of the quark-gluon plasma after the phase transition is large enough to produce a significant rate of nucleation of hadrons.
Book•
01 Feb 1992
TL;DR: In this paper, Einasto et al. presented a large scale structure of the universe based on primordial nucleosynthesis and the microwave sky, and the abundances of light elements.
Abstract: 1. Lectures on the very early universe V. N. Lukash and I. D. Novikov 2. Primordial nucleosynthesis Hubert Reeves 3. Big Bang nucleosynthesis and abundances of light elements Bernard E. J. Pagel 4. The microwave sky Jose Luis Sanz 5. The large scale structure of the universe Bernard J. T. Jones 6. Large-scale structure of the universe Jaan Einasto.
Journal Article•
TL;DR: Differential cross-section data for the 8 Li(p, α) 5 He reaction at 1.5 MeV center-of-mass energy, measured with a (radioactive) 8 Li beam, were used to calculate one of the terms of the thermonuclear reaction rate for destruction of 8 Li.
TL;DR: In this paper, the authors studied the effects of recently calculated baryon diffusion coefficients on the yields of primordial light elements in Baryon-inhomogeneous big-bang models and found that the largest effect of these new coefficients on nucleosynthesis is through neutron-proton scattering.
TL;DR: In this article, the authors studied new physical phenomena and constraints in generalized scalar-tensor theories of gravity with variable masses and found an entropy increase effect during the matter era and a measurable effect on the motion of the halo of spiral galaxies.
Abstract: We study new physical phenomena and constraints in generalized scalar--tensor theories of gravity with $\Phi$--dependent masses. We investigate a scenario (which can arise in string theories) with two types of $\Phi$--dependent masses which could correspond to visible and dark matter sectors. The parameters of this theory are constrained from post--Newtonian bounds, primordial nucleosynthesis and the age of the Universe. We present a perfect fluid formalism for the dark matter sector with variable masses and find an entropy increase effect during the matter era and, in principle, a measurable effect on the motion of the halo of spiral galaxies. For the case of string effective theories, the constancy of gauge couplings provide new bounds which are orders of magnitude stronger than the previous ones.
TL;DR: In this article, the authors proposed generalized couplings of a dark matter component to the Jordan-Brans-Dicke, or dilaton, field, and used observational data on the rate of change of Newton's constant, as well as on its value during primordial nucleosynthesis, on the age of the Universe and on the present value of the Hubble constant.
TL;DR: In this article, a detailed calculation of light element production in scale-covariant FRW cosmological models, where the modifications in the equations of nuclear kinetics due to scale-consistency theory effects are taken into account, is presented.
Abstract: A detailed calculation of light element production in scale-covariant FRW cosmological models, where the modifications in the equations of nuclear kinetics due to scale-covariant kinetic theory effects are taken into account, is presented. The comparison of the results of our calculation with current observational data implies that the gauge function β(t) at primordial nucleosynthesis cannot deviate from its present value by more than a 1.5%. If we assume, as usual, that β is a power of time, these bounds leave little room for a possible strong equivalence principle violation
TL;DR: In this article, a detailed discussion of the constraints that the primordial abundances of light elements impose on the interactions of light scalars which are relativistic at the time of nucleosynthesis is presented.
TL;DR: In this article, the development of experimental studies on explosive nucleosynthesis, especially the rapid proton process and the primordial nuclear synthesis were discussed with a stress on unstable nuclei.
01 Jan 1992
TL;DR: In this paper, the observational status in evaluating the interstellar deuterium abundance was reviewed and it was shown that the most reasonable value is of the order of 10-5, which is in general agreement with the standard Big Bang nucleosynthesis.
Abstract: We review the observational status in evaluating the interstellar deuterium abundance and show that the most reasonable value is of the order of 10-5 . Although in general agreement with the standard Big Bang nucleosynthesis, the situation is still unclear and deserves much more observations.
TL;DR: In this paper, the high-lying levels of 12 B have been studied via the 9 Be(α, p) 12 B reaction using 65 MeV α-particles, and the reaction protons were analyzed with a quadrupole-dipole-diagram spectrograph, yielding a resolution of about 40 keV.
01 Jan 1992
TL;DR: In this paper, the dependence of primordial abundances of D, 3 He, 4 He and 7 Li on the mean baryonic density of the universe and dependence of 4 He on the number of neutrino families and the neutron half-life are discussed.
Abstract: Big Bang nucleosynthesis (BBNS) theory is sketched, indicating the dependence of primordial abundances of D, 3 He, 4 He and 7 Li on the mean baryonic density of the universe and the dependence of 4 He on the number of neutrino families and the neutron half-life. Observational data and inferred primordial abundances of these elements are reviewed and shown to be consistent (within errors) either with standard BBNS in a homogeneous universe about 100 seconds after the Big Bang or with moderately inhomogeneous BBNS models resulting from earlier phase transitions like the quark-hadron transition if this is first order. However, models with closure density supplied by baryons are apparently ruled out. Finally, implications for the existence of baryonic and non-baryonic dark matter are briefly discussed.
TL;DR: In this paper, it was shown that the primordial yields of D, 3He, 4He and 7Li far exceed the upper limits inferred from observation, unless baryogenesis is anterior to the freeze-out of the weak interactions.
TL;DR: In this paper, it was shown that dark matter with variable masses can have a measurable effect on the dynamical motion of the halo of spiral galaxies, which may affect cold dark matter models of galaxy formation.
Abstract: String effective theories contain a dilaton scalar field which couples to gravity, matter and radiation. In general, particle masses will have different dilaton couplings. We can always choose a conformal frame in which baryons have constant masses while (non--baryonic) dark matter have variable masses, in the context of a scalar--tensor gravity theory. We are interested in the phenomenology of this scenario. Dark matter with variable masses could have a measurable effect on the dynamical motion of the halo of spiral galaxies, which may affect cold dark matter models of galaxy formation. As a consequence of variable masses, the energy--momentum tensor is not conserved; there is a dissipative effect, due to the dilaton coupling, associated with a ``dark entropy" production. In particular, if axions had variable masses they could be diluted away, thus opening the ``axion window". Assuming that dark matter with variable masses dominates the cosmological evolution during the matter era, it will affect the primordial nucleosynthesis predictions on the abundances of light elements. Furthermore, the dilaton also couples to radiation in the form of a variable gauge coupling. Experimental bounds will constrain the parameters of this model.