The success of primordial nucleosynthesis as a cornerstone of the hot Big Bang model has been limited by the long-standing lithium problem. Recent work presented a self-consistent perturbative analysis of the effects of variations in nature's fundamental constants on primordial nucleosynthesis for a broad class of grand unified theory models, showing that such models provide a possible solution to the lithium problem, provided the value of the fine-structure constant $α$ at the nucleosynthesis epoch is larger than the current laboratory one by a few parts per million of relative variation. Here we extend the earlier analysis, focusing on how this preferred value of $α$ is affected if relevant cosmological parameters are also allowed to vary--specifically focusing on the baryon-to-photon ratio, the number of neutrinos, and the neutron lifetime. We rephrase the lithium problem in terms of the values of these parameters that would be needed to solve it within this class of grand unified theories, thus obtaining values that would disagree with the results of other experiments by several standard deviations. Using these experimental results as priors in the analysis, we find that a larger value of $α$ is still preferred, confirming our previous results. By excluding lithium from the analysis, we also obtain upper limits on possible variations of $α$ at the primordial nucleosynthesis epoch. At the two-sigma level, these are $|Δα/α|<50$ ppm without nuclear physics, cosmology, or atomic clocks priors, or alternatively $|Δα/α|<5$ ppm if these priors are used. While the simplest solution to the lithium problem is likely to be found within observational astrophysics, our work shows that varying fundamental constants remain a viable alternative.
During the era of primordial nucleosynthesis the background of non-equilibrium antineutrinos is being formed due to decays of neutrons and nuclei of tritium. The spectra of antineutrinos of this background were calculated taking into account the Coulomb interaction between electron and daughter nucleus in $β^-$-decay. The dependence of these spectra on the value of the baryon-to-photon ratio $η$ at the period of primordial nucleosynthesis is investigated. The observations of these antineutrinos will allow us to look directly at the very early Universe and nonequilibrium processes taken place b…
The success of primordial nucleosynthesis has been limited by the long-standing Lithium problem. We use a self-consistent perturbative analysis of the effects of relevant theoretical parameters on primordial nucleosynthesis, including variations of nature's fundamental constants, to explore the problem and its possible solutions, in the context of the latest observations and theoretical modeling. We quantify the amount of depletion needed to solve the Lithium problem, and show that transport processes of chemical elements in stars are able to account for it. Specifically, the combination of at…
Primordial nucleosynthesis is an observational cornerstone of the Hot Big Bang model and a sensitive probe of physics beyond the standard model. Its success has been limited by the so-called Lithium problem, for which many solutions have been proposed. We report on a self-consistent perturbative analysis of the effects of variations in nature's fundamental constants, which are unavoidable in most extensions of the standard model, on primordial nucleosynthesis, focusing on a broad class of Grand Unified Theory models. A statistical comparison between theoretical predictions and observational me…
We analyze the influence of decaying sterile neutrinos with the masses in the range 1-140 MeV on the primordial Helium-4 abundance, explicitly solving the Boltzmann equations for all particle species, taking into account neutrino flavour oscillations, and paying special attention to systematic uncertainties. We show that the Helium abundance depends only on the sterile neutrino lifetime and not on the way the active-sterile mixing is distributed between flavours, and derive an upper bound on the lifetime. We also demonstrate that the recent results of Izotov & Thuan [arXiv:1001.4440], who find…
Abundances of light nuclei formed during primordial nucleosynthesis are predicted by Standard Big Bang Model. The latest data from WMAP, with precision's higher than ever before, provides a motivation to determine theoretical higher order corrections to change in helium abundance and the related parameters. Here we evaluate the QED corrections to the change in these parameters during primordial nucleosynthesis using finite temperature effects at the two loop level. Relative variations in neutron decay rate, total energy density of the universe, relative change in neutrino temperature etc., wit…
The cosmic microwave background (CMB) spectrum provides tight constraints on the thermal history of the universe up to $z \sim 2\times 10^6$. At higher redshifts thermalization processes become very efficient so that even large energy releases do not leave visible imprints in the CMB spectrum. In this paper we show that the consistency between the accurate determinations of the specific entropy at primordial nucleosynthesis and at the electron-photon decoupling implies that no more than 7.8% of the present day CMB energy density could have been released in the post-nucleosynthesis era. As poin…
Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the three evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations, and calculated in primordial nucleosynthesis. However, there remains a yet-unexplained discrepancy of a factor 3, between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor …
For a brief time in its early evolution the Universe was a cosmic nuclear reactor. The expansion and cooling of the Universe limited this epoch to the first few minutes, allowing time for the synthesis in astrophysically interesting abundances of only the lightest nuclides (D, 3He, 4He, 7Li). For big bang nucleosynthesis (BBN) in the standard models of cosmology and particle physics (SBBN), the SBBN-predicted abundances depend on only one adjustable parameter, the baryon density parameter (the ratio by number of baryons (nucleons) to photons). The predicted and observed abundances of the relic…
We present a parametrized study of the effects of free thermal neutron injection on primordial nucleosynthesis, where both the rate and the time scale of injection are varied. This generic approach is found to yield a successful solution for reducing the 7Li abundance without causing significant problems to other elemental abundances. Our analysis demonstrates that hadronic injection, possibly due to decays or annihilations of dark matter particles with a mass of about 1 to 30 GeV, provides a possible solution to an outstanding problem in the standard Big Bang model.
During its early evolution the Universe provided a laboratory to probe fundamental physics at high energies. Relics from those early epochs, such as the light elements synthesized during primordial nucleosynthesis when the Universe was only a few minutes old, and the cosmic background photons, last scattered when the protons (and alphas) and electrons (re)combined some 400 thousand years later, may be used to probe the standard models of cosmology and of particle physics. The internal consistency of primordial nucleosynthesis is tested by comparing the predicted and observed abundances of the …
5D models with one 3D brane and one infinite extra dimension are studied. Matter is confined to the brane, gravity extends to the bulk. Models with positive and negative tension of the brane are studied. Cosmological solutions on the brane are obtained by solving the generalized Friedmann equation. As the input in cosmological solutions we use the present-time observational cosmological parameters. We find constraints on dimensionless combinations of scales of 5D models which follow from the requirement that the models reproduce the data on production of ${}^4 He$ in primordial nucleosynthesis…
For the first time the antineutrino spectrum formed as a result of neutron and tritium decays during the epoch of primordial nucleosynthesis is calculated. This spectrum is a non-thermal increase in addition to the standard cosmic neutrino background (C$ν$B) whose thermal spectrum was formed before the beginning of primordial nucleosynthesis. For energy larger than $10^{-2}\,$eV the calculated non-thermal antineutrino flux exceeds the C$ν$B spectrum and there are no other comparable sources of antineutrino in this range. The observations of these antineutrinos will allow us to look directly at…
We study the effects of dark-matter annihilation during the epoch of big-bang nucleosynthesis on the primordial abundances of light elements. We improve the calculation of the light-element abundances by taking into account the effects of anti-nucleons emitted by the annihilation of dark matter and the interconversion reactions of neutron and proton at inelastic scatterings of energetic nucleons. Comparing the theoretical prediction of the primordial light-element abundances with the latest observational constraints, we derive upper bounds on the dark-matter pair-annihilation cross section. Im…
We propose a correction of the standard Big Bang nucleosynthesis (BBN) scenario to resolve the primordial lithium problem by considering a possibility that the primordial plasma can deviate from the ideal state. In the standard BBN, the primordial plasma is assumed to be ideal, with particles and photons satisfying the Maxwell-Boltzmann and Planck distribution, respectively. We suggest that this assumption of the primordial plasma being ideal might oversimplify the early Universe and cause the lithium problem. We find that deviation of photon distribution from the Planck distribution, which is…
The $^7$Li abundance calculated in BBN with the baryon-to-photon ratio fixed from fits to the CMB power spectrum is inconsistent with the observed lithium abundances on the surface of metal-poor halo stars. Previous cosmological solutions proposed to resolve this $^7$Li problem include photon cooling (possibly via the Bose-Einstein condensation of a scalar particle) or the decay of a long-lived $X-$particle (possibly the next-to-lightest supersymmetric particle). In this paper we reanalyze these solutions, both separately and in concert. We also introduce the possibility of a primordial magnet…
Primordial or big bang nucleosynthesis (BBN) is now a parameter free theory whose predictions are in good overall agreement with observations. However, the 7Li calculated abundance is significantly higher than the one deduced from spectroscopic observations. Most solutions to this lithium problem involve a source of extra neutrons that inevitably leads to an increase of the deuterium abundance. This seems now to be excluded by recent deuterium observations that have drastically reduced the uncertainty on D/H and also calls for improved precision on thermonuclear reaction rates.
We calculate the weak interaction rates of selected light nuclei during the epoch of Big Bang Nucleosynthesis (BBN), and we assess the impact of these rates on nuclear abundance flow histories and on final light element abundance yields. We consider electron and electron antineutrino captures on 3He and 7Be, and the reverse processes of positron capture and electron neutrino capture on 3H and 7Li. We also compute the rates of positron and electron neutrino capture on 6He. We calculate beta and positron decay transitions where appropriate. As expected, the final standard BBN abundance yields ar…
In the present work, we discuss the effects of the inclusion of sterile-active neutrino oscillations during the production of primordial light-nuclei. We assume that the sterile neutrino mass-eigenstate might oscillate with the two lightest active neutrino mass- eigenstates, with mixing angles $ϕ_1$ and $ϕ_2$. We also allow a constant renormalization (represented by a parameter ($ζ$)) of the sterile neutrino occupation factor. Taking $ζ$ and the mixing angles as free parameters, we have computed distribution functions of active and sterile neutrinos and primordial abundances. Using observable …
Primordial nucleosynthesis is rightly hailed as one of the great successes of the standard cosmological model. Here we consider the initial forging of elements in the recently proposed Rh = ct universe, a cosmology that demands linear evolution of the scale factor. Such a universe cools extremely slowly compared to standard cosmologies, considerably depleting the available neutrons during nucleosynthesis; this has significant implications for the resultant primordial abundances of elements, predicting a minuscule quantity of helium which is profoundly at odds with observations. The production …
In the primordial Universe, neutrino decoupling occurs only slightly before electron-positron annihilations, leading to an increased neutrino energy density with order $10^{-2}$ spectral distortions compared to the standard instantaneous decoupling approximation. However, there are discrepancies in the literature on the impact it has on the subsequent primordial nucleosynthesis, in terms of both the magnitude of the abundance modifications and their sign. We review how neutrino decoupling indirectly affects the various stages of nucleosynthesis, namely, the freezing out of neutron abundance, t…
A change in the fundamental constants of nature or plasma effects in the early universe could stabilize $^8$Be against decay into two $^4$He nuclei. Coc et al. examined this effect on big bang nucleosynthesis as a function of $B_8$, the mass difference between two $^4$He nuclei and a single $^8$Be nucleus, and found no effects for $B_8 \le 100$ keV. Here we examine stable $^8$Be with larger $B_8$ and also allow for a variation in the rate for $^4$He + $^4$He $\longrightarrow$ $^8$Be to determine the threshold for interesting effects. We find no change to standard big bang nucleosynthesis for $…
We study the dependence of primordial nuclear abundances on fundamental nuclear observables such as binding energies, scattering lengths, neutron lifetime, \textit{etc.} by varying these quantities. The numerical computations were performed with four publicly available codes, thus facilitating an investigation of the model-dependent (systematic) uncertainties on these dependences. Indeed deviations of the order of a few percent are found. Moreover, accounting for the temperature dependence of the sensitivity of the rates to some relevant parameters leads to a reduction of the sensitivity of th…
We discuss a constraint on the scale $Λ_{\rm NC}$ of noncommutative (NC) gauge field theory arising from consideration of the big bang nucleosynthesis (BBN) of light elements. The propagation of neutrinos in the NC background described by an antisymmetric tensor $θ^{μν}$ does result in a tree-level vector-like coupling to photons in a generation-independent manner, raising thus a possibility to have an appreciable contribution of three light right-handed (RH) fields to the energy density of the universe at nucleosynthesis time. Considering elastic scattering processes of the RH neutrinos off c…
We revisit the decoupling of neutrinos in the early universe with flavour oscillations. We rederive the quantum kinetic equations which determine the neutrino evolution based on a BBGKY-like hierarchy, and include for the first time the full collision term, with both on- and off-diagonal terms for all relevant reactions. We focus on the case of zero chemical potential and solve these equations numerically. We also develop an approximate scheme based on the adiabatic evolution in the matter basis. In fact, the large difference between the oscillations and cosmological time scales allows to cons…
Primordial nucleosynthesis, or Big-Bang Nucleosynthesis (BBN), is one of the three evidences for the Big-Bang model, together with the expansion of the Universe and the Cosmic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations, and calculated in primordial nucleosynthesis. This comparison was used to determine the baryonic density of the Universe. For this purpose, it is now superseded by the analysis of the Cosmic Microwave Background (CMB) radiation anisotropies. However, there re…
Assuming the best numerical value for the cosmic baryonic density and the existence of three neutrino flavors, standard big bang nucleosynthesis is a parameter-free model. It is important to assess if the observed primordial abundances can be reproduced by simulations. Numerous studies have shown that the simulations overpredict the primordial $^7$Li abundance by a factor of $\approx$ $3$ compared to the observations. The discrepancy may be caused by unknown systematics in $^7$Li observations, poorly understood depletion of lithium in stars, errors in thermonuclear rates that take part in the …
During its early evolution, the hot, dense Universe provided a laboratory for probing fundamental physics at high energies. By studying the relics from those early epochs, such as the light elements synthesized during primordial nucleosynthesis when the Universe was only a few minutes old, and the relic, cosmic microwave photons, last scattered when the protons, alphas, and electrons (re)combined some 400 thousand years later, the evolution of the Universe may be used to test the standard models of cosmology and particle physics and to set constraints on proposals of physics beyond these stand…
A new upper limit on the amplitude of primordial magnetic field (PMF) is derived by a comparison between a calculation of elemental abundances in big bang nucleosynthesis (BBN) model and the latest observational constraints on the abundances. Updated nuclear reaction rates are adopted in the calculation. Effects of PMF on the abundances are consistently taken into account in the numerical calculation with the precise formulation of changes in physical variables. We find that abundances of 3He and 6Li increase while that of 7Li decreases when the PMF amplitude increases, in the case of the bary…
Primordial nucleosynthesis remains as one of the pillars of modern cosmology. It is the testing ground upon which many cosmological models must ultimately rest. It is our only probe of the universe during the important radiation-dominated epoch in the first few minutes of cosmic expansion. This chapter reviews the basic equations of space-time, cosmology, and big bang nucleosynthesis. We also summarize the current state of observational constraints on primordial abundances along with the key nuclear reactions and their uncertainties. We summarize which nuclear measurements are most crucial dur…
We present a new determination of the primordial helium mass fraction Yp, based on 93 spectra of 86 low-metallicity extragalactic HII regions, and taking into account the latest developments concerning systematic effects. These include collisional and fluorescent enhancements of HeI recombination lines, underlying HeI stellar absorption lines, collisional and fluorescent excitation of hydrogen lines and temperature and ionization structure of the HII region. Using Monte Carlo methods to solve simultaneously for the above systematic effects, we find the best value to be Yp=0.2565+/-0.0010(stat.…
We extensively reanalyze effects of a long-lived negatively charged massive particle, X-, on big bang nucleosynthesis (BBN). The BBN model with an X- particle was originally motivated by the discrepancy between 6,7Li abundances predicted in standard BBN model and those inferred from observations of metal-poor stars. In this model 7Be is destroyed via the recombination with an X- particle followed by radiative proton capture. We calculate precise rates for the radiative recombinations of 7Be, 7Li, 9Be, and 4He with X-. In nonresonant rates we take into account respective partial waves of scatte…
Primordial or Big Bang nucleosynthesis (BBN) is one of the three historical strong evidences for the Big-Bang model together with the expansion of the Universe and the Cosmic Microwave Background radiation (CMB). The recent results by the Planck mission have slightly changed the estimate of the baryonic density Omega_b, compared to the previous WMAP value. This article updates the BBN predictions for the light elements using the new value of Omega_b determined by Planck, as well as an improvement of the nuclear network and new spectroscopic observations. While there is no major modification, t…
As space expands, the energy density in black holes increases relative to that of radiation, providing us with motivation to consider scenarios in which the early universe contained a significant abundance of such objects. In this study, we revisit the constraints on primordial black holes derived from measurements of the light element abundances. Black holes and their Hawking evaporation products can impact the era of Big Bang Nucleosynthesis (BBN) by altering the rate of expansion at the time of neutron-proton freeze-out, as well as by radiating mesons which can convert protons into neutrons…
Big Bang Nucleosynthesis (BBN) offers one of the most strict evidences for the Lambda-CDM cosmology at present, as well as the Cosmic Microwave Background (CMB) radiation. In this work, our main aim is to present the outcomes of our calculations related to primordial abundances of light elements, in the context of higher dimensional steady-state universe model in the dilaton gravity. Our results show that abundances of light elements (primordial D, 3He, 4He, T, 7Li) are significantly different for some cases, and a comparison is given between a particular dilaton gravity model and Lambda-CDM i…
Big bang nucleosynthesis (BBN) is affected by the energy density of a primordial magnetic field (PMF). For an easy derivation of constraints on models for PMF generations, we assume a PMF with a power law (PL) distribution in wave number defined with a field strength, a PL index, and maximum and minimum scales at a generation epoch. We then show a relation between PL-PMF parameters and the scale invariant (SI) strength of PMF for the first time. We perform a BBN calculation including PMF effects, and show abundances as a function of baryon to photon ratio $η$. The SI strength of the PMF is con…
Primordial or big bang nucleosynthesis (BBN) is one of the three historical strong evidences for the big bang model. The recent results by the Planck satellite mission have slightly changed the estimate of the baryonic density compared to the previous WMAP analysis. This article updates the BBN predictions for the light elements using the cosmological parameters determined by Planck, as well as an improvement of the nuclear network and new spectroscopic observations. There is a slight lowering of the primordial Li/H abundance, however, this lithium value still remains typically 3 times larger …
Nuclear reaction rates are among the most important input for understanding the primordial nucleosynthesis and therefore for a quantitative description of the early Universe. An up-to-date compilation of direct cross sections of 2H(d,p)3H, 2H(d,n)3He, 7Li(p,alpha)4He and 3He(d,p)4He reactions is given. These are among the most uncertain cross sections used and input for Big Bang nucleosynthesis calculations. Their measurements through the Trojan Horse Method (THM) are also reviewed and compared with direct data. The reaction rates and the corresponding recommended errors in this work were used…
The theoretical predictions of the primordial abundances of elements in the big-bang nucleosynthesis (BBN) are dominated by uncertainties in the input nuclear reaction rates. We investigate the effect of modifying these reaction rates on light element abundance yields in BBN by replacing the thirty-five reaction rates out of the existing eighty-eight. We have studied these yields as functions of evolution time or temperature. We find that using these new reaction rates results in only a little increase in helium mass fraction over that obtained previously in BBN calculations. This allows insig…
We present constraints on the number of relativistic species from a joint analysis of cosmic microwave background (CMB) fluctuations and light element abundances (helium and deuterium) compared to big bang nucleosynthesis (BBN) predictions. Our BBN calculations include updates of nuclear rates in light of recent experimental and theoretical information, with the most significant change occuring for the d(p,gamma)^3He cross section. We calculate a likelihood function for BBN theory and observations that accounts for both observational errors and nuclear rate uncertainties and can be easily embe…
We show that some or all of the inventory of $r$-process nucleosynthesis can be produced in interactions of primordial black holes (PBHs) with neutron stars (NSs) if PBHs with masses ${10}^{-14}\,{\rm M}_\odot < {\rm M}_{\rm PBH} < {10}^{-8}\,{\rm M}_\odot$ make up a few percent or more of the dark matter. A PBH captured by a neutron star (NS) sinks to the center of the NS and consumes it from the inside. When this occurs in a rotating millisecond-period NS, the resulting spin-up ejects $\sim 0.1-0.5\,{\rm M}_{\odot}$ of relatively cold neutron-rich material. This ejection process and the acco…
We investigate the effect of a variation of fundamental constants on primordial element production in Big Bang nucleosynthesis (BBN). We focus on the effect of a possible change in the nucleon-nucleon interaction on nuclear reaction rates involving the A=5 (5Li and 5He) and A=8 (8Be) unstable nuclei. The reaction rates for 3He(d,p)4He and 3H(d,n)4He are dominated by the properties of broad analog resonances in 5Li and 5He compound nuclei respectively. While the triple-alpha process 4He(aa,g)12C is normally not effective in BBN, its rate is very sensitive to the position of the "Hoyle state" an…
The possibility that a relevant fraction of the dark matter might be comprised of Primordial Black Holes (PBHs) has been seriously reconsidered after LIGO's detection of a $\sim 30 M_{\odot}$ binary black holes merger. Despite the strong interest in the model, there is a lack of studies on possible cosmological implications and effects on cosmological parameters inference. We investigate correlations with the other standard cosmological parameters using cosmic microwave background observations, finding significant degeneracies, especially with the tilt of the primordial power spectrum and the …
We investigate the effect on the Big Bang Nucleosynthesis (BBN) from the presence of a stochastic primordial magnetic field (PMF) whose strength is spatially inhomogeneous. We assume a uniform total energy density and a gaussian distribution of field strength. In this case, domains of different temperatures exist in the BBN epoch due to variations in the local PMF. We show that in such case, the effective distribution function of particle velocities averaged over domains of different temperatures deviates from the Maxwell-Boltzmann distribution. This deviation is related to the scale invariant…
The conventional approach to search for departures from the standard model of physics during Big Bang Nucleosynthesis involves a careful, and subtle measurement of the mass fraction of baryons consisting of helium. Recent measurements of this quantity tentatively support new physics beyond the standard model but, historically, this method has suffered from hidden systematic uncertainties. In this letter, I show that a combined measurement of the primordial deuterium abundance and the primordial helium isotope ratio has the potential to provide a complementary and reliable probe of new physics …
We calculate the radiative capture cross section for $^7$Be($α, γ$)$^{11}$C and its reaction rate of relevance for the big bang nucleosynthesis. The impact of this reaction on the primordial $^7$Li abundance is revised including narrow and broad resonances in the pertinent energy region. Our calculations show that it is unlikely that very low energy resonances in $^{11}$C of relevance for the big bang nucleosynthesis would emerge within a two-body potential model. Based on our results and a comparison with previous theoretical and experimental analyses, we conclude that the impact of this reac…
