Primordial nucleosynthesis as a probe of fundamental physics parameters
Thomas Dent, Steffen Stern, Christof Wetterich
备注：
v2: 34 pages, 2 figures, typo in last GUT scenario corrected, added discussion and graph of nonlinear behaviour in GUT scenarios, added short section discussing binding of dineutron and 8Be, refs added, conclusions unaltered. Accepted for publication, Phys. Rev. D
We analyze the effect of variation of fundamental couplings and mass scales on primordial nucleosynthesis in a systematic way. The first step establishes the response of primordial element abundances to the variation of a large number of nuclear physics parameters, including nuclear binding energies. We find a strong influence of the n-p mass difference (for the 4He abundance), of the nucleon mass (for deuterium) and of A=3,4,7 binding energies (for 3He, 6Li and 7Li). A second step relates the nuclear parameters to the parameters of the Standard Model of particle physics. The deuterium, and, above all, 7Li abundances depend strongly on the average light quark mass hat{m} \equiv (m_u+m_d)/2. We calculate the behaviour of abundances when variations of fundamental parameters obey relations arising from grand unification. We also discuss the possibility of a substantial shift in the lithium abundance while the deuterium and 4He abundances are only weakly affected.
A detailed analysis of primordial nucleosynthesis predictions for light element abundances is performed. Contents: 1. The standard cosmology: an overview. 2. Primordial nucleosynthesis. 3. The Born rates for n<->p reactions. 4. Finite nucleon mass corrections. 5. QED thermal radiative corrections. 6. Calculations of Big Bang Nucleosynthesis. Results.
We study here the effect of a varying G on the evolution of the early Universe and, in particular, on primordial nucleosynthesis. This variation of G is modelled using the Brans-Dicke theory as well as a more general class of scalar-tensor theories. Modified nucleosynthesis codes are used to investigate this effect and the results obtained are used to constrain the parameters of the theories. We extend previous studies of primordial nucleosynthesis in scalar-tensor theories by including effects which can cause a slow variation of G during radiation domination and by including a late-time accel…
We report on the results of a recent evaluation of all percent level corrections to weak rates of processes converting n <-> p, which are crucial for the determination of the 4He mass fraction produced during primordial nucleosynthesis.
We report the results of a detailed calculation of nucleon weak interactions relevant for the neutron to proton density ratio at the onset of primordial nucleosynthesis. Radiative electromagnetic corrections, finite nucleon mass terms, thermal radiative effects on weak processes and on neutrino temperature are taken into account to reduce the theoretical uncertainty on $n \leftrightarrow p $ rates to 1%. This translates into a sensitivity in $^4 He$ mass fraction $Y_p$ prediction up to $10^{-4}$. We find a positive total correction to the Born prediction $δY_p \simeq 0.004$.
We report the results of a new accurate evaluation of light nuclei yields in primordial nucleosynthesis. The relic densities of 4He, D and 7Li have been numerically obtained via a new updated version of the standard BBN code.
We review the Cosmology and Physics underlying Primordial Nucleosynthesis and survey current observational data in order to compare the predictions of Big Bang Nucleosynthesis with the inferred primordial abundances. From this comparison we report on the status of the consistency of the standard hot big bang model, we constrain the universal density of baryons (nucleons), and we set limits to the numbers and/or effective interactions of hypothetical new "light" particles (equivalent massless neutrinos).
The synthesis of helium in the early Universe depends on many input parameters, including the value of the gravitational coupling during the period when the nucleosynthesis takes place. We compute the primordial abundance of helium as function of the gravitational coupling, using a semi-analytical method, in order to track the influence of $G$ in the primordial nucleosynthesis. To be specific, we construct a cosmological model with varying $G$, using the Brans-Dicke theory. The greater the value of $G$ at nucleosynthesis period, the greater the abundance of helium predicted. Using the observat…
We report the results of a recent likelihood analysis combining the primordial nucleosynthesis and the BOOMERanG and MAXIMA-1 data on cosmic microwave background radiation anisotropies. We discuss the possible implications for relic neutrino background of a high value for the baryonic matter content of the universe, larger than what is expected in a standard nucleosynthesis scenario.
Using the semi-analytic method proposed by \citet{Esma91} we calculate the abundances of the light elements produced during primordial nucleosynthesis assuming that the gauge coupling constants of the fundamental interactions may vary. We analyze the dependence of the nucleon masses, nuclear binding energies and cross sections involved in the calculation of the abundances with the fundamental constants assuming the chiral limit of QCD. The abundances of light elements as a function of the fundamental constants are obtained. Finally, using the observational data of $\De$, $\Het$, $\He$ and $\Li…
An up to date review of Standard Big Bang Nucleosynthesis predictions vs the astrophysical estimates of light nuclei abundances is here presented. In particular the analysis reports the expected ranges for baryon fraction and effective number of neutrinos as obtained by BBN only.
Primordial nucleosynthesis calculations are shown to be able to provide constraints on electroweak baryogenesis which produce a highly inhomogeneous distribution of the baryon-to-photon ratio. Such baryogenesis scenarios overproduce 4He and/or 7Li and can be ruled out whenever a fraction f<3*10e-6(100 GeV/T)^3 of nucleated bubbles of broken-symmetry phase contributes > 10% of the baryon number within the horizon volume.
We use the constraints arising from primordial nucleosynthesis to bound the strength $F$ of non-standard neutrino-neutrino interactions, when the right-handed neutrinos participate in the interaction. We find $F < 3 \times 10^{-3}\ G_F$, which is five orders of magnitude more stringent than the limit obtained using LEP data. We also show that secret interactions of neutrinos mediated by massless particles must have a coupling $f$ less than $2 \times 10^{-5}$. This also ameliorates previous limits in the literature.
A new accurate evaluation of primordial light nuclei abundances is presented. The proton to neutron conversion rates have been corrected to take into account radiative effects, finite nucleon mass, thermal and plasma corrections. The theoretical uncertainty on 4He is so reduced to the order of 0.1%.
We examine in detail the changes in the production of primordial helium resulting from nonthermal neutrino momentum distributions produced by resonant transformation of electron-type neutrinos to steriles. These transformations, anti-nu_e -> anti-nu_s (nu_e->nu_s), amplify a positive (negative) lepton number asymmetry. We find that the resulting supression relative to a thermal distribution of low energy nu_e reduces n -> p conversion to a greater extent than does the enhancement of n -> p from an identical suppression of anti-nu_e. Thus, equal lepton-number asymmetries of opposite sign have u…
We investigate the influence of hadron injection from evaporating primordial black holes (PBHs) in the early stage of the primordial nucleosynthesis era (t = 10^{-3} - 10^4 sec). The emitted quark-antiquark pairs or gluons immediately fragment into a lot of hadrons and scatter off the thermal plasma which is constituted by photons, electrons and nucleons. For the relatively low mass holes we point out that the dominant effect is the inter-conversion between ambient proton and neutron through the strong interaction induced by the emitted hadrons. Even after the freeze-out time of the week inter…
The cosmological abundance of nucleons determined from considerations of Big Bang nucleosynthesis allegedly provides compelling evidence for non-nucleonic dark matter. Recent developments in measurements of primordial light element abundances, in particular deuterium and helium, require reexamination of this important issue. The present situation is uncertain but exciting.
The discrepancy between the experimental decay rate of orthopositronium (o-Ps) and the QED theoretical prediction can be solved by invoking decays of o-Ps into exotic particles with branching ratios of the order of 10^{-3}. We show that considerations based on primordial nucleosynthesis and effective Lagrangians place a very stringent upper bound: B = Gamma(o-Ps -> ``exotic'' + ...)/Gamma(o-Ps) <= 2 x 10^{-15}, ruling out the exotic decay solution to the puzzle.
We have modified the standard code for primordial nucleosynthesis to include the effect of finite nucleon mass on the weak-interaction rates as calculated by Seckel \cite{seckel}. We find a small, systematic increase in the $^4$He yield, $ΔY \simeq 0.0057\,Y$, which is insensitive to the value of the baryon-to-photon ratio $η$ and slightly larger than Seckel's estimate. The fractional changes in the abundances of D, $^3$He, and $^7$Li range from 0.08\% to 3\% for $10^{-11}\le η\le 10^{-8}$.
We show that the presence of primordial stochastic (hypercharge) magnetic fields before the electroweak (EW) phase transition induces isocurvature fluctuations (baryon number inhomogeneities). Depending on the details of the magnetic field spectrum and on the particle physics parameters (such as the strength of the EW phase transition and electron Yukawa couplings) these fluctuations may survive until the Big Bang nucleosynthesis (BBN). Their lenghtscale may exceed the neutron diffusion length at that time, while their magnitude can be so large that sizable antimatter domains are present. This…
We report on the status of primordial nucleosynthesis in light of recent results on CMB anisotropies from WMAP experiment. Theoretical estimates for nuclei abundances, along with the corresponding uncertainties, are evaluated using a new numerical code, where all nuclear rates usually considered have been updated using the most recent available data. Moreover, additional processes, neglected in previous calculations, have been included. The combined analysis of CMB and primordial nucleosynthesis prediction for Deuterium gives an effective number of relativistic degrees of freedom in good agree…
We have modified the standard code for primordial nucleosynthesis to include the effect of the slight heating of neutrinos by $e^\pm$ annihilations. There is a small, systematic change in the $^4$He yield, $ΔY \simeq +1.5\times 10^{-4}$, which is insensitive to the value of the baryon-to-photon ratio $η$ for $10^{-10}\la η\la 10^{-9}$. We also find that the baryon-to-photon ratio decreases by about 0.5\% less than the canonical factor of 4/11 because some of the entropy in $e^\pm$ pairs is transferred to neutrinos. These results are in accord with recent analytical estimates.
We study the primordial nucleosynthesis and cosmic age in the presence of a net lepton asymmetry as well as baryon asymmetry. We explore a previously unnoted region of the parameter space in which very large baryon densities $0.1 \le Ω_b \le 1$ can be accommodated within the light-element constraints from primordial nucleosynthesis. This parameter space consists of $ν_μ$ and $ν_τ$ degeneracies with a small $ν_e$ degeneracy. Constraints from cosmic microwave background fluctuations are also discussed (orito00).
A comprehensive study of the effect of an unstable tau neutrino on primordial nucleosynthesis is presented. The standard code for nucleosynthesis is modified to allow for a massive decaying tau neutrino whose daughter products include neutrinos, photons, $e^\pm$ pairs, and/or noninteracting (sterile) daughter products. Tau-neutrino decays influence primordial nucleosynthesis in three distinct ways: (i) the energy density of the decaying tau neutrino and its daughter products affect the expansion rate tending to increase $^4$He, D, and $^3$He production; (ii) electromagnetic (EM) decay products…
We calculate and display the primordial light-element abundances as a function of a neutrino degeneracy parameter ξcommon to all flavors. It is the only unknown parameter characterizing the thermal medium at the primordial nucleosynthesis epoch. The observed primordial helium abundance Y_p is the most sensitive cosmic ``leptometer.'' Adopting the conservative Y_p error analysis of Olive and Skillman implies -0.04 \alt ξ\alt 0.07 whereas the errors stated by Izotov and Thuan imply ξ=0.0245+-0.0092 (1 sigma). Improved determinations of the baryon abundance have no significant impact on this situ…
We present a detailed calculation of the light element production in the framework of Scalar-Tensor (ST) theories of gravitation. The coupling function ωhas been described by an appropriate form which reproduces all the possible asymptotic behaviors at early times of viable ST cosmological models with a monotonic ω(Φ). This form gives an exact representation for most of the particular theories proposed in the literature, but also a first-order approximation to many other theories. In most of ST theories, the nucleosynthesis bounds lead to cosmological models which do not significantly differ f…
In this paper, we revisit in detail the effects of primordial magnetic fields on big bang nucleosynthesis (BBN) including a discussion of the magnetic field geometry and the anomalous magnetic moment. The presence of magnetic fields affects BBN by (1) increasing the weak reaction rates; (2) increasing the electron density due to changes to the electron phase space; and (3) by increasing the expansion rate of the universe, due both to the magnetic field energy density and to the modified electron energy density. Of the effects considered, the increase in the expansion rate due to the magnetic f…
We examine effects on primordial nucleosynthesis from a truly random spatial distribution in the baryon-to-photon ratio ($η$). We generate stochastic fluctuation spectra characterized by different spectral indices and root-mean-square fluctuation amplitudes. For the first time we explicitly calculate the effects of baryon diffusion on the nucleosynthesis yields of such stochastic fluctuations. We also consider the collapse instability of large-mass-scale inhomogeneities. Our results are generally applicable to any primordial mechanism producing fluctuations in $η$ which can be characterized by…
Big Bang Nucleosynthesis (BBN) is the synthesis of the light nuclei, Deuterium, He3, He4 and Li7, during the first few minutes of the universe. This review concentrates on recent improvements in the measurement of the primordial (after BBN, and prior to modification) abundances of these nuclei. We mention improvement in the standard theory, and the non-standard extensions which are limited by the data. (abridged)
We discuss the possible ranges of electron neutrino degeneracy which is consistent with the inferred primordial abundances of the light elements. It is found that the electron neutrino degeneracy, $|ξ_e|$, up to order of $10^{-1}$ is consistent with the present data.
We investigate the possibility that inhomogeneous nucleosynthesis may eventually be used to explain the abundances of \li6, \be9 and B in population II stars. The present work differs from previous studies in that we have used a more extensive reaction network. It is demonstrated that in the simplest scenario the abundances of the light elements with $A\le7$ constrain the separation of inhomogeneities to sufficiently small scales that the model is indistinguishable from homogeneous nucleosynthesis and that the abundances of \li6, \be9\ and B are then below observations by several orders of mag…
We present an up-to-date review of Big Bang Nucleosynthesis (BBN). We discuss the main improvements which have been achieved in the past two decades on the overall theoretical framework, summarize the impact of new experimental results on nuclear reaction rates, and critically re-examine the astrophysical determinations of light nuclei abundances. We report then on how BBN can be used as a powerful test of new physics, constraining a wide range of ideas and theoretical models of fundamental interactions beyond the standard model of strong and electroweak forces and Einstein's general relativit…
A massive long-lived tau neutrino in the MeV regime modifies the primordial light-element abundances predicted by big-bang nucleosynthesis (BBN) calculations. This effect has been used to derive limits on the tau neutrino mass. Because recently the observational situation has become somewhat confusing and, in part, intrinsically inconsistent, we reconsider the BBN limits on the tau neutrino mass. To this end we use our newly developed BBN code to calculate the primordial abundances as a function of the tau neutrino mass and of the cosmic baryon density eta. We derive concordance regions in the…
We report the results on Big Bang Nucleosynthesis (BBN) based on an updated code, with accuracy of the order of 0.1% on He4 abundance, compared with the predictions of other recent similar analysis. We discuss the compatibility of the theoretical results, for vanishing neutrino chemical potentials, with the observational data. Bounds on the number of relativistic neutrinos and baryon abundance are obtained by a likelihood analysis. We also analyze the effect of large neutrino chemical potentials on primordial nucleosynthesis, motivated by the recent results on the Cosmic Microwave Background R…
Catalysis of nuclear reactions by metastable charged particles X^- opens the possibility for primordial production of elements with A>7. We calculate the abundance of ^9Be, where synthesis is mediated by the formation of (^8Be X^-) bound states, finding a dramatic enhancement over the standard BBN prediction: ^9Be/^1H = 10^{-13}\times(Y_X/10^{-5}). Thus observations of ^9Be abundances at low metallicity offers a uniquely sensitive probe of many particle physics models that predict X^-, including variants of supersymmetric models. Comparing the catalytically-enhanced abundances of primordial ^6…
We analyze in details the standard Primordial Nucleosynthesis scenario. In particular we discuss the key theoretical issues which are involved in a detailed prediction of light nuclide abundances, as the weak reaction rates, neutrino decoupling and nuclear rate modeling. We also perform a new analysis of available data on the main nuclear processes entering the nucleosynthesis reaction network, with particular stress on their uncertainties as well as on their role in determining the corresponding uncertainties on light nuclide theoretical estimates. The current status of theoretical versus exp…
In the standard hot big bang model, the expansion of the early universe is given by the Friedmann equation with an energy density dominated by relativistic particles. Since in a variety of models this equation is altered, we introduce modifications in the Friedmann equation and show that we can constrain them using big bang nucleosynthesis data. When there is no neutrino/antineutrino asymmetry these modifications are tightly bounded but in presence of an asymmetry the bounds become much looser. As an illustration, we apply our results to a model where the second and third families couple to gr…
We determine the restrictions imposed by primordial nucleosynthesis upon a heavy tau neutrino, in the presence of nu-tau annihilations into Majorons, as expected in a wide class of particle physics models of neutrino mass. We determine the equivalent number of light neutrino species $N_{eq}$ as a function of nu-tau mass and the nu-tau-Majoron coupling $g$. We show that for theoretically plausible $g$ values $\gsim 10^{-4}$ present nucleosynthesis observations can not rule out nu-tau masses in the MeV range. Moreover, these models give $N_{eq} \leq 3$ in the nu-tau mass region 1-10 MeV, for ver…
We study the effect from a general ultralocal supermetric on primordial nucleosynthesis for Friedmann-Robertson-Walker Cosmology. The parameter $λ$ of the supermetric changes the effective number of degrees of freedom, $g_*$, which modifies the Friedmann equation. This modification produces variations in the production of primordial $^4He$. The observations of the primordial abundances of light elements ($^4He$, $D$, $^3He$ and $^7Li$) allow to estimate bounds on the values of $λ$ consistent with these observations. We obtain $0.87 \le λ\le 1.04$. In addition we analyze the importance of $λ< 1…
We have calculated the small effect of finite nucleon mass on the weak-interaction rates that interconvert protons and neutrons in the early Universe. We have modified the standard code for primordial nucleosynthesis to include these corrections and find a small, systematic increase in the 4He yield, $δY / Y \simeq (0.47 - 0.50)% $, depending slightly on the baryon-to-photon ratio. The fractional changes in the abundances of the other light elements are a few percent or less for interesting values of the baryon-to-photon ratio.
The annihilation of new dark matter candidates with masses $m_X$ in the MeV range may account for the galactic positrons that are required to explain the 511 keV $γ$-ray flux from the galactic bulge. We study the impact of MeV-mass thermal relic particles on the primordial synthesis of $^2$H, $^4$He, and $^7$Li. If the new particles are in thermal equilibrium with neutrinos during the nucleosynthesis epoch they increase the helium mass fraction for $m_X\alt 10$ MeV and are thus disfavored. If they couple primarily to the electromagnetic plasma they can have the opposite effect of lowering both…
It is known that, theoretically, the Rees-Sciama effect may cause arbitrarily large additional redshifts in the cosmic microwave background radiation due to transparent expanding voids having sizes comparable with the size of horizon. Therefore, again theoretically, eventual huge voids existing immediately after the recombination may essentially change the predictions of the theory of big bang nucleosynthesis. If this eventuality holds, then the dark matter can be dominantly baryonic and, simultaneously, one can be in accordance with the predictions of primordial nucleosynthesis theory. Studyi…
We describe a program for computing the abundances of light elements produced during Big Bang Nucleosynthesis which is publicly available at http://parthenope.na.infn.it/. Starting from nuclear statistical equilibrium conditions the program solves the set of coupled ordinary differential equations, follows the departure from chemical equilibrium of nuclear species, and determines their asymptotic abundances as function of several input cosmological parameters as the baryon density, the number of effective neutrino, the value of cosmological constant and the neutrino chemical potential. The pro…
The catalysis of nuclear reactions by negatively charged relics leads to increased outputs of primordial ^6Li and ^9Be. In combination with observational constraints on the primordial fractions of ^6Li and ^9Be, this imposes strong restrictions on the primordial abundance and the lifetime of charged relics. We analyze the constraints from the catalysis of ^9Be on supersymmetric models in which the gravitino is the lightest supersymmetric particle and a charged slepton--such as the lighter stau--the next-to-lightest supersymmetric particle (NLSP). Barring the special cases in which the primordi…
We examine inhomogeneous primordial nucleosynthesis for {\it arbitrary} distributions $f$ of the baryon-to-photon ratio $η$, in the limit where neither particle diffusion nor gravitational collapse is important. By discretizing $f(η)$ and using linear programming, we show that for a set of $m$ constraints on the primordial element abundances, the maximum and minimum possible values of $\bar η$ (the final mean value of $η$) are given when $f(η)$ is a sum of at most $m+1$ delta functions. Our linear programming results indicate that when $f$ is taken to be an arbitrary function, there is no lowe…
We derive a general master equation relating the gravitational-wave observables r and Omega_gw(f). Here r is the tensor-to-scalar ratio, constrained by cosmic-microwave-background (CMB) experiments; and Omega_gw(f) is the energy spectrum of primordial gravitational-waves, constrained e.g. by pulsar-timing measurements, laser-interferometer experiments, and Big Bang Nucleosynthesis (BBN). Differentiating the master equation yields a new expression for the tilt d(ln Omega_gw(f))/d(ln f). The relationship between r and Omega_gw(f) depends sensitively on the uncertain physics of the early universe…
We discuss effects of fluctuation geometry on primordial nucleosynthesis. For the first time we consider condensed cylinder and cylindrical-shell fluctuation geometries in addition to condensed spheres and spherical shells. We find that a cylindrical shell geometry allows for an appreciably higher baryonic contribution to be the closure density ($Ω_b h_{50}^2 \la 0.2$) than that allowed in spherical inhomogeneous or standard homogeneous big bang models. This result, which is contrary to some other recent studies, is due to both geometry and recently revised estimates of the uncertainties in th…
The apparent discrepancy between abundances of light nuclides predicted by the standard Big-Bang and observational data is explained, by assuming the presence of metastable H dibaryons at the nucleosynthesis era. These dibaryons could be formed out of a small fraction of strange quarks at the moment of the confinement transition. For a primordial deuterium abundance of the order of 3 10^{-5}, the measured differences in the 4He abundances requires a relative abundance of H dibaryons of the order of n_H/n_B = 0.07, decaying in a timescale of the order of 10^5 s.
Primordial nucleosynthesis provides a probe of the Universe during its early evolution. Given the progress exploring the constituents, structure, and recent evolution of the Universe, it is timely to review the status of Big Bang Nucleosynthesis (BBN) and to confront its predictions, along with the constraints which emerge from them, with those derived from independent observations of the Universe at much later epochs in its evolution. Following an overview of the key physics controlling element synthesis in the early Universe, the predictions of BBN in the standard models of cosmology and par…
The physics of the standard hot big bang cosmology ensures that the early Universe was a primordial nuclear reactor, synthesizing the light nuclides (D, 3He, 4He, and 7Li) in the first 20 minutes of its evolution. After an overview of nucleosynthesis in the standard model (SBBN), the primordial abundance yields will be presented, followed by a status report (intended to stimulate further discussion during this symposium) on the progress along the road from observational data to inferred primordial abundances. Theory will be confronted with observations to assess the consistency of SBBN and to …
We present a simple method for determining the (correlated) uncertainties of the light element abundances expected from big bang nucleosynthesis, which avoids the need for lengthy Monte Carlo simulations. Our approach helps to clarify the role of the different nuclear reactions contributing to a particular elemental abundance and makes it easy to implement energy-independent changes in the measured reaction rates. As an application, we demonstrate how this method simplifies the statistical estimation of the nucleon-to-photon ratio through comparison of the standard BBN predictions with the obs…
Primordial nucleosynthesis provides a probe of the Universe during its early evolution. Given the progress exploring the constituents, structure, and recent evolution of the Universe, it is timely to review the status of Big Bang Nucleosynthesis (BBN) and to confront its predictions, and the constraints which emerge from them, with those derived from independent observations of the Universe at much later epochs in its evolution. Following an overview of the key physics controlling element synthesis in the early Universe, the predictions of the standard models of cosmology and particle physics …
We study post weak decoupling coherent active-sterile and active-active matter-enhanced neutrino flavor transformation in the early universe. We show that flavor conversion efficiency at Mikheyev-Smirnov-Wolfenstein resonances is likely to be high (adiabatic evolution) for relevant neutrino parameters and energies. However, we point out that these resonances cannot sweep smoothly and continuously with the expansion of the universe. We show how neutrino flavor conversion in this way can leave both the active and sterile neutrinos with non-thermal energy spectra, and how, in turn, these distorte…
The neutrino role in primordial nucleosynthesis is reviewed. The importance of nonequilibrium effects is emphasized both for the standard massless and possibly massive neutrinos. The upper bound on tau neutrino mass is presented. A spatial variation of primordial abundances and a possibility of observing them by precise measurements of the CMB anisotropy are considered.The nucleosynthesis bounds on the parameters of neutrino oscillations into sterile neutrinos are discussed.
Big Bang Nucleosynthesis is the theory of the production of the the light element isotopes of D, He3, He4, and Li7. After a brief review of the essential elements of the standard Big Bang model at a temperature of about 1 MeV, the theoretical input and predictions of BBN are discussed. The theory is tested by the observational determinations of the light element abundances and the current status of these observations is reviewed. Concordance of standard model and the related observations is found over a limited range of the baryon-to-photon ratio, the single true parameter of the standard mode…
We show that a class of inhomogeneous big bang nucleosynthesis models exist which yield light-element abundances in agreement with observational constraints for baryon-to-photon ratios significantly smaller than those inferred from standard homogeneous big bang nucleosynthesis (HBBN). These inhomogeneous nucleosynthesis models are characterized by a bimodal distribution of baryons in which some regions have a local baryon-to-photon ratio eta=3*10e-10, while the remaining regions are baryon-depleted. HBBN scenarios with primordial (2H+3He)/H<9*10e-5 necessarily require that most baryons be in a…
We present a detailed study of inhomogeneous Big Bang nucleosynthesis where, for the first time, nuclear reactions are coupled to all significant fluctuation dissipation processes. Theses processes include neutrino heat transport, baryon diffusion, photon diffusive heat transport, and hydrodynamic expansion with photon-electron Thomson drag. Light element abundance yields are presented for broad ranges of initial amplitudes and length scales for spherically condensed fluctuations. The $^2$H, $^3$He, $^4$He, and $^7$Li nucleosynthesis yields are found to be inconsistent with observationally inf…
We derive constraints on the strength of a new intermediate range interaction that couples to baryon number from primordial nucleosynthesis yields. The nucleosysnthesis limits here used arise from matching observations and predictions of standard and inhomogeneous primordial scenarios. We show that the standard nucleosynthesis scenario is more restrictive ($α_5 \lsim 0.2$) when the range of the interaction is greater than about 1 m. We further discuss the implications of considering the scalar particle responsible for the new interaction as the main component of the dark matter in the galactic…
Cosmic microwave background (CMB) determinations of the baryon-to-photon ratio $η\propto Ω_{\rm baryon} h^2$ will remove the last free parameter from (standard) big bang nucleosynthesis (BBN) calculations. This will make BBN a much sharper probe of early universe physics, for example, greatly refining the BBN measurement of the effective number of light neutrino species, $N_{ν,eff}$. We show how the CMB can improve this limit, given current light element data. Moreover, it will become possible to constrain $N_{ν,eff}$ independent of \he4, by using other elements, notably deuterium; this will a…
We study big bang nucleosynthesis in the presence of large mass-scale, non-linear entropy fluctuations. Overdense regions, with masses above the local baryon-Jeans mass, are expected to collapse and form condensed objects. Surviving nucleosynthesis products therefore tend to originate from underdense regions. We compute expected surviving light element ($^2$H, $^3$He, $^4$He, $^7$Li) abundance yields for a variety of stochastic fluctuation spectra. In general, we find that spectra with significant power in fluctuations on length scales below that of the local baryon Jeans mass produce nucleosy…
Recent confrontations of the predictions of standard big bang nucleosynthesis (SBBN) with the primordial abundances of the light nuclides inferred from observational data reveal a conflict. Simply put, compared to theoretical expectations the inferred primordial abundances of either deuterium or helium-4 (or both) are ``too small". Here I outline the ``tension" between D and $^4$He in the context of SBBN. The incipient crisis for SBBN may be resolved by observations of deuterium in nearly pristine environments such as the high-redshift, low-metallicity QSO absorbers. At present the big bang ab…
