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1
Schramm, D. N. "Big Bang Nucleosynthesis". Symposium - International Astronomical Union 187 (2002): 1–15. http://dx.doi.org/10.1017/s0074180900113695.
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Big Bang Nucleosynthesis (BBN) is on the verge of undergoing a transformation now that extragalactic deuterium is being measured. Previously, the emphasis was on demonstrating the concordance of the Big Bang Nucleosynthesis model with the abundances of the light isotopes extrapolated back to their primordial values using stellar and Galactic evolution theories. Once the primordial deuterium abundance is converged upon, the nature of the field will shift to using the much more precise primordial D/H to constrain the more flexible stellar and Galactic evolution models (although the question of potential systematic error in 4He abundance determinations remains open). The remarkable success of the theory to date in establishing the concordance has led to the very robust conclusion of BBN regarding the baryon density. The BBN constraints on the cosmological baryon density are reviewed and demonstrate that the bulk of the baryons are dark and also that the bulk of the matter in the universe is non-baryonic. Comparison of baryonic density arguments from Lyman-α clouds, x-ray gas in clusters, the Sunyaev-Zeldovich effect, and the microwave anisotropy are made and shown to be consistent with the BBN value.
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Steigman, Gary. "Neutrinos and Big Bang Nucleosynthesis". Advances in High Energy Physics 2012 (2012): 1–24. http://dx.doi.org/10.1155/2012/268321.
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According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders this neutrino background undetectable with current technology. The cosmic neutrino background can, however, be probed indirectly through its cosmological effects on big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) radiation. In this BBN review, focused on neutrinos and more generally on dark radiation, the BBN constraints on the number of “equivalent neutrinos” (dark radiation), on the baryon asymmetry (baryon density), and on a possible lepton asymmetry (neutrino degeneracy) are reviewed and updated. The BBN constraints on dark radiation and on the baryon density following from considerations of the primordial abundances of deuterium and helium-4 are in excellent agreement with the complementary results from the CMB, providing a suggestive, but currently inconclusive, hint of the presence of dark radiation, and they constrain any lepton asymmetry. For all the cases considered here there is a “lithium problem”: the BBN-predicted lithium abundance exceeds the observationally inferred primordial value by a factor of~3.
3
Foley, M., N. Sasankan, M. Kusakabe i G. J. Mathews. "Revised uncertainties in Big Bang Nucleosynthesis". International Journal of Modern Physics E 26, nr 08 (sierpień 2017): 1741008. http://dx.doi.org/10.1142/s0218301317410087.
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Big Bang Nucleosynthesis (BBN) explores the first few minutes of nuclei formation during the Big Bang. We present updated 2[Formula: see text] for the abundances of the four primary light nuclides — D, 3He, 4He, and 7Li — in BBN. A modified standard BBN code was used in a Monte Carlo analysis of the nucleosynthesis uncertainties as a function of the baryon-to-photon ratio. Reaction rates were updated to those of NACRE, REACLIB, and [Formula: see text]-Matrix calculations. The results were then used to derive a new constraint on the effective number of neutrinos.
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Pospelov, M. "Catalyzed Big-Bang nucleosynthesis". Canadian Journal of Physics 86, nr 4 (1.04.2008): 611–16. http://dx.doi.org/10.1139/p07-206.
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We point out that the existence of metastable, τ >103 s, negatively charged electroweak-scale particles (X–) alters the predictions for lithium and other primordial elemental abundances for A > 4 via the formation of bound states with nuclei during Big-Bang nucleosynthesis (BBN). In particular, we show that the bound states of X– with helium, formed at temperatures of about T = 108 K, lead to the catalytic enhancement of 6Li production, which is eight orders of magnitude more efficient than the standard channel. In particle physics models, where subsequent decay of X– does not lead to large nonthermal BBN effects, this directly translates to the level of sensitivity to the number density of long-lived X– particles (τ > 105 s) relative to entropy of nX – / s [Formula: see text] 3 × 10–17, which is one of the most stringent probes of electroweak scale remnants known to date. It is also argued that unstable charged particles with lifetime of order ~2000 s may naturally lead to the depletion of 7Li by a factor of two, making it consistent with observationally determined abundances. PACS No.: 98.80.Ft
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Coc, Alain, i Elisabeth Vangioni. "Primordial nucleosynthesis". International Journal of Modern Physics E 26, nr 08 (sierpień 2017): 1741002. http://dx.doi.org/10.1142/s0218301317410026.
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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 [Formula: see text], between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor by new observations. The precision in deuterium observations in cosmological clouds has recently improved dramatically, so that nuclear cross-sections involved in deuterium BBN needs to be known with similar precision. We will briefly discuss nuclear aspects related to the BBN of Li and D, BBN with nonstandard neutron sources, and finally, improved sensitivity studies using a Monte Carlo method that can be used in other sites of nucleosynthesis.
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Yeh, Tsung-Han, Keith A. Olive i Brian D. Fields. "The Neutron Mean Life and Big Bang Nucleosynthesis". Universe 9, nr 4 (12.04.2023): 183. http://dx.doi.org/10.3390/universe9040183.
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We explore the effect of neutron lifetime and its uncertainty on standard big bang nucleosynthesis (BBN). BBN describes the cosmic production of the light nuclides, 1H, D, 3H+3He, 4He, and 7Li+7Be, in the first minutes of cosmic time. The neutron mean life τn has two roles in modern BBN calculations: (1) it normalizes the matrix element for weak n↔p interconversions, and (2) it sets the rate of free neutron decay after the weak interactions freeze-out. We review the history of the interplay between τn measurements and BBN, and present a study of the sensitivity of the light element abundances to the modern neutron lifetime measurements. We find that τn uncertainties dominate the predicted 4He error budget, but these theory errors remain smaller than the uncertainties in 4He observations, even with the dispersion in recent neutron lifetime measurements. For the other light element predictions, τn contributes negligibly to their error budget. Turning the problem around, we combine present BBN and cosmic microwave background (CMB) determinations of the cosmic baryon density to predict a “cosmologically preferred” mean life of τn(BBN+CMB)=870±16s, which is consistent with experimental mean life determinations. We show that if future astronomical and cosmological helium observations can reach an uncertainty of σobs(Yp)=0.001 in the 4He mass fraction Yp, this could begin to discriminate between the mean life determinations.
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Hwang, Eunseok, Dukjae Jang, Kiwan Park, Motohiko Kusakabe, Toshitaka Kajino, A. Baha Balantekin, Tomoyuki Maruyama, Chang-Mo Ryu i Myung-Ki Cheoun. "Dynamical screening effects on big bang nucleosynthesis". Journal of Cosmology and Astroparticle Physics 2021, nr 11 (1.11.2021): 017. http://dx.doi.org/10.1088/1475-7516/2021/11/017.
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Abstract A moving ion in plasma creates a deformed electric potential depending on the ion velocity, which leads to the distinct screening effect compared to the standard static Salpeter formula. In this paper, adopting the test charge method, we explore the dynamical screening effects on big bang nucleosynthesis (BBN). We find that the high temperature in the early universe causes the ion velocity to be faster than the solar condition so that the electric potential is effectively polarized. However, the low density of background plasma components significantly suppresses the dynamical screening effects on thermonuclear reaction rates during the BBN epoch. We compare our results with several thermonuclear reaction rates for solar fusion considering the dynamical screening effects. Also, we discuss the additional plasma properties in other astrophysical sites for the possible expansion from the present calculation in the future.
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VILLANTE, F. L. "BBN AND NEUTRINO OSCILLATIONS IN THE EARLY UNIVERSE: A BRIEF REVIEW". International Journal of Modern Physics A 20, nr 11 (30.04.2005): 2431–35. http://dx.doi.org/10.1142/s0217751x05024729.
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KAMIMURA, M., Y. KINO i E. HIYAMA. "STAU-CATALYZED BIG-BANG NUCLEOSYNTHESIS AND NUCLEAR CLUSTER MODEL". International Journal of Modern Physics A 24, nr 11 (30.04.2009): 2076–83. http://dx.doi.org/10.1142/s0217751x09045649.
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Three-body cluster-model calculations are performed for the new types of big-bang nucleosynthesis (BBN) reactions that are calalyzed by a supersymmetric (SUSY) particle stau, a scalar partner of the tau lepton. If a stau has a lifetime ≳ 103s, it would capture a light element previously synthesized in standard BBN and form a Coulombic bound state. The bound state, an exotic atom, is expected to induce various reactions, such as (αX-) + d → 6 Li + X-, in which a negatively charged stau (denoted as X-) works as a catalyzer. Recent literature papers have claimed that some of these stau-catalyzed reactions have significantly large cross sections so that inclusion of the reactions into the BBN network calculation can change drastically abundances of some elements, giving not only a solution to the 6 Li -7 Li problem (calculated underproduction of 6 Li by ~ 1000 times and overproduction of 7 Li +7 Be by ~ 3 times) but also a constraint on the lifetime and the primordial abundance of the elementary particle stau. However, most of these literature calculations of the reaction cross sections were made assuming too naive models or approximations that are unsuitable for those complicated low-energy nuclear reactions. We use a few-body calculational method developed by the authors, and provides precise cross sections and rates of the stau-catalyzed BBN reactions for the use in the BBN network calculation.
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Makki, Tahani, i Mounib El Eid. "Big Bang Nucleosynthesis (BBN) and Non-Standard Physics". EPJ Web of Conferences 184 (2018): 02009. http://dx.doi.org/10.1051/epjconf/201818402009.
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A brief overview on standard big bang nucleosynthesis (shortly, SBBN) is presented. First, we describe the outcome of the SBBN concerning the abundances of the light elements up to 7Li. A comparison with observations reveals a Lithium overproduction, which is not understood yet and is termed as “Cosmological Lithium Problem”. Resolving that problem is not easy, since many aspects are involved whichnuclear, astrophysical and even a non-standard scenario may be invoked. These items are described in some details owing to the limited available space.
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Asimakis, Petros, Emmanuel N. Saridakis, Spyros Basilakos i Kuralay Yesmakhanova. "Big Bang Nucleosynthesis Constraints on f(T,TG) Gravity". Universe 8, nr 9 (14.09.2022): 486. http://dx.doi.org/10.3390/universe8090486.
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We confront f(T,TG) gravity, with big bang nucleosynthesis (BBN) requirements. The former is obtained using both the torsion scalar, as well as the teleparallel equivalent of the Gauss–Bonnet term, in the Lagrangian, resulting to modified Friedmann equations in which the extra torsional terms constitute an effective dark energy sector. We calculate the deviations of the freeze-out temperature Tf, caused by the extra torsion terms in comparison to ΛCDM paradigm. Then, we impose five specific f(T,TG) models and extract the constraints on the model parameters in order for the ratio |ΔTf/Tf| to satisfy the observational BBN bound. As we find, in most of the models the involved parameters are bounded in a narrow window around their general relativity values as expected, asin the power-law model, where the exponent n needs to be n≲0.5. Nevertheless, the logarithmic model can easily satisfy the BBN constraints for large regions of the model parameters. This feature should be taken into account in future model building.
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Kusakabe, Motohiko, Toshitaka Kajino, Takashi Yoshida i Grant J. Mathews. "Big Bang nucleosynthesis with long-lived strongly interacting relic particles". Proceedings of the International Astronomical Union 5, S268 (listopad 2009): 33–38. http://dx.doi.org/10.1017/s1743921310003832.
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AbstractWe study effects of relic long-lived strongly interacting massive particles (X particles) on big bang nucleosynthesis (BBN). The X particle is assumed to have existed during the BBN epoch, but decayed long before detected. The interaction strength between an X and a nucleon is assumed to be similar to that between nucleons. Rates of nuclear reactions and beta decay of X-nuclei are calculated, and the BBN in the presence of neutral charged X0 particles is calculated taking account of captures of X0 by nuclei. As a result, the X0 particles form bound states with normal nuclei during a relatively early epoch of BBN leading to the production of heavy elements. Constraints on the abundance of X0 are derived from observations of primordial light element abundances. Particle models which predict long-lived colored particles with lifetimes longer than ~200 s are rejected. This scenario prefers the production of 9Be and 10B. There might, therefore, remain a signature of the X particle on primordial abundances of those elements. Possible signatures left on light element abundances expected in four different models are summarized.
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Kohri, K., M. Kawasaki i Katsuhiko Sato. "Big Bang Nucleosynthesis and Lepton Number Asymmetry in the Universe". Symposium - International Astronomical Union 183 (1999): 312. http://dx.doi.org/10.1017/s0074180900133030.
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Recently it has been reported that there may be a discrepancy between big bang nucleosynthesis theory and observations (BBN crisis) (Hata et al., 1995). One way to solve the discrepancy might be to adopt some modifications of standard physics used in SBBN (Kawasaki et al, 1997). We show that BBN predictions agree with the primordial abundances of light elements, 4He, D, 3He and 7Li inferred from the observational data if the electron neutrino has a net chemical potential ξve due to lepton asymmetry (Kohri et al., 1997). We study BBN with the effects of the neutrino degeneracy in details using Monte Carlo simulation and make a likelihood analysis using the most recent data. We estimate that (95% C.L.) and (95% C.L.) adopting the presolar Deuterium abundance as the primordial values. If we adopted the low D abundance which is obtained by the observation of the high redshift QSO absorption systems, (95% C.L.) and The estimated chemical potential of ve is about 10−5 eV which is much smaller than experiments can detect (≃ 1 eV). In other words, BBN gives the most stringent constraint on the chemical potential of ve.
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Jang, Dukjae, Youngshin Kwon, Kyujin Kwak i Myung-Ki Cheoun. "Big Bang nucleosynthesis in a weakly non-ideal plasma". Astronomy & Astrophysics 650 (czerwiec 2021): A121. http://dx.doi.org/10.1051/0004-6361/202038478.
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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 a deviation of photon distribution from the Planck distribution, which is parameterised with the help of Tsallis statistics, can resolve the primordial lithium problem when the particle distributions of the primordial plasma still follow the Maxwell-Boltzmann distribution. We discuss how the primordial plasma can be weakly non-ideal in this specific fashion and its effects on the cosmic evolution.
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KUSAKABE, MOTOHIKO, TOSHITAKA KAJINO, RICHARD N. BOYD, TAKASHI YOSHIDA i GRANT J. MATHEWS. "EFFECT OF NEGATIVELY-CHARGED MASSIVE PARTICLES ON BIG-BANG NUCLEOSYNTHESIS AND A SOLUTION TO THE LITHIUM PROBLEMS". Modern Physics Letters A 23, nr 17n20 (28.06.2008): 1668–74. http://dx.doi.org/10.1142/s0217732308028077.
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Spectroscopic observations of metal poor halo stars give an indication of a possible primordial plateau of 6 Li abundance as a function of metallicity similar to that for 7 Li . The inferred abundance of 6 Li is ~1000 times larger than that predicted by standard big bang nucleosynthesis (BBN) for the baryon-to-photon ratio inferred from the WMAP data, and that of 7 Li is about 3 times smaller than the prediction. We study a possible solution to both the problems of underproduction of 6 Li and overproduction of 7 Li in BBN. This solution involves a hypothetical massive, negatively-charged particle that would bind to the light nuclei produced in BBN. The particle gets bound to the existing nuclei after the usual BBN, and a second epoch of nucleosynthesis can occur among nuclei bound to the particles. We numerically carry out a fully dynamical BBN calculation, simultaneously solving the recombination and ionization processes of negatively-charged particles by normal and particle-bound nuclei as well as many possible nuclear reactions among them. It is confirmed that BBN in the presence of these hypothetical particles can solve the two Li abundance problems simultaneously.
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Pitrou, Cyril, Alain Coc, Jean-Philippe Uzan i Elisabeth Vangioni. "A new tension in the cosmological model from primordial deuterium?" Monthly Notices of the Royal Astronomical Society 502, nr 2 (20.01.2021): 2474–81. http://dx.doi.org/10.1093/mnras/stab135.
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ABSTRACT Recent measurements of the D(p,γ)3He nuclear reaction cross-section and of the neutron lifetime, along with the reevaluation of the cosmological baryon abundance from cosmic microwave background (CMB) analysis, call for an update of abundance predictions for light elements produced during the big-bang nucleosynthesis (BBN). While considered as a pillar of the hot big-bang model in its early days, BBN constraining power mostly rests on deuterium abundance. We point out a new ≃1.8σ tension on the baryonic density, or equivalently on the D/H abundance, between the value inferred on one hand from the analysis of the primordial abundances of light elements and, on the other hand, from the combination of CMB and baryonic oscillation data. This draws the attention on this sector of the theory and gives us the opportunity to reevaluate the status of BBN in the context of precision cosmology. Finally, this paper presents an upgrade of the BBN code primat.
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Park, Tae-Sun, Kyung Joo Min i Seung-Woo Hong. "Effects of transient nonthermal particles on the big bang nucleosynthesis". International Journal of Modern Physics E 29, nr 03 (marzec 2020): 2050012. http://dx.doi.org/10.1142/s0218301320500123.
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The effects of introducing a small amount of nonthermal distribution (NTD) of elements in big bang nucleosynthesis (BBN) are studied by allowing a fraction of the NTD to be time-dependent so that it contributes only during a certain period of the BBN evolution. The fraction is modeled as a Gaussian-shaped function of [Formula: see text], where [Formula: see text] is the temperature of the cosmos, and thus the function is specified by three parameters; the central temporal position, the width and the magnitude. The change in the average nuclear reaction rates due to the presence of the NTD is assumed to be proportional to the Maxwellian reaction rates but with temperature [Formula: see text], [Formula: see text] being another parameter of our model. By scanning a wide four-dimensional parametric space at about half a million points, we have found about 130 points with [Formula: see text], at which the predicted primordial abundances of light elements are consistent with the observations. The magnitude parameter [Formula: see text] of these points turns out to be scattered over a very wide range from [Formula: see text] to [Formula: see text], and the [Formula: see text]-parameter is found to be strongly correlated with the magnitude parameter [Formula: see text]. The temperature region with [Formula: see text] or the temporal region [Formula: see text][Formula: see text]s seems to play a central role in lowering [Formula: see text].
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STEIGMAN, GARY. "PRIMORDIAL NUCLEOSYNTHESIS: SUCCESSES AND CHALLENGES". International Journal of Modern Physics E 15, nr 01 (luty 2006): 1–35. http://dx.doi.org/10.1142/s0218301306004028.
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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 (SBBN) are presented, along with those from some non-standard models. The observational data used to infer the primordial abundances are described, with an emphasis on the distinction between precision and accuracy. These relic abundances are compared with predictions, testing the internal consistency of BBN and enabling a comparison of the BBN constraints with those derived from the WMAP Cosmic Background Radiation data. Emerging from these comparisons is a successful standard model along with constraints on (or hints of) physics beyond the standard models of particle physics and of cosmology.
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Bertulani, Carlos A., Francis W. Hall i Benjamin I. Santoyo. "Big Bang nucleosynthesis as a probe of new physics". EPJ Web of Conferences 275 (2023): 01003. http://dx.doi.org/10.1051/epjconf/202327501003.
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The Big Bang Nucleosynthesis (BBN) model is a cornerstone for the understanding of the evolution of the early universe, making seminal predictions that are in outstanding agreement with the present observation of light element abundances in the universe. Perhaps, the only remaining issue to be solved by theory is the so-called “lithium abundance problem". Dedicated experimental efforts to measure the relevant nuclear cross sections used as input of the model have lead to an increased level of accuracy in the prediction of the light element primordial abundances. The rise of indirect experimental techniques during the preceding few decades has permitted the access of reaction information beyond the limitations of direct measurements. New theoreticaldevelopments have also opened a fertile ground for tests of physics beyond the standard model of atomic,nuclear, statistics, and particle physics. We review the latest contributions of our group for possible solutions of the lithium problem.
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Olive, Keith A. "The effects of coupling variations on BBN". Proceedings of the International Astronomical Union 5, H15 (listopad 2009): 305. http://dx.doi.org/10.1017/s1743921310009452.
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AbstractThe effect of variations of the fundamental nuclear parameters on big-bang nucleosynthesis are modeled and discussed in detail taking into account the interrelations between the fundamental parameters arising in unified theories. Considering only 4He, strong constraints on the variation of the neutron lifetime, neutron-proton mass difference are set. We show that a variation of the deuterium binding energy is able to reconcile the 7Li abundance deduced from the WMAP analysis with its spectroscopically determined value while maintaining concordance with D and 4He.
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Kusakabe, Motohiko, Grant J. Mathews, Toshitaka Kajino i Myung-Ki Cheoun. "Review on effects of long-lived negatively charged massive particles on Big Bang Nucleosynthesis". International Journal of Modern Physics E 26, nr 08 (sierpień 2017): 1741004. http://dx.doi.org/10.1142/s021830131741004x.
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We review important reactions in the Big Bang Nucleosynthesis (BBN) model involving a long-lived negatively charged massive particle, [Formula: see text], which is much heavier than nucleons. This model can explain the observed 7Li abundances of metal-poor stars, and predicts a primordial 9Be abundance that is larger than the standard BBN prediction. In the BBN epoch, nuclei recombine with the [Formula: see text] particle. Because of the heavy [Formula: see text] mass, the atomic size of bound states [Formula: see text] is as small as the nuclear size. The nonresonant recombination rates are then dominated by the [Formula: see text]-wave [Formula: see text] transition for 7Li and [Formula: see text]Be. The 7Be destruction occurs via a recombination with the [Formula: see text] followed by a proton capture, and the primordial 7Li abundance is reduced. Also, the 9Be production occurs via the recombination of 7Li and [Formula: see text] followed by deuteron capture. The initial abundance and the lifetime of the [Formula: see text] particles are constrained from a BBN reaction network calculation. We derived parameter region for the 7Li reduction allowed in supersymmetric or Kaluza–Klein (KK) models. We find that either the selectron, smuon, KK electron or KK muon could be candidates for the [Formula: see text] with [Formula: see text] TeV, while the stau and KK tau cannot.
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Luo, Yudong, Toshitaka Kajino, Motohiko Kusakabe i Michael A Famiano. "Primordial Nucleosynthesis with a background magnetic field". EPJ Web of Conferences 227 (2020): 02003. http://dx.doi.org/10.1051/epjconf/202022702003.
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We present our recent detailed calculation of the impacts from a background magnetic field on Big Bang Nucleosynthesis (BBN). Namely, the magnetic field impacts on the electron-positron thermodynamics, time temper-ature relation and the screening potential of the early Universe. Most interest-ingly, we investigated the electron-positron relativistic screening potential with the background magnetic field, such potential might lead to a non trivial effect on the electron capture reaction which could finally affect the neutron to proton ratio.
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Sabeeh, Syeda, Muhammad Jawad, Abdul Kabir i Jameel-Un Nabi. "Re-examination of radiative capture of deuteron 3He(d,γ)5Li at low energy". Europhysics Letters 141, nr 5 (1.03.2023): 54003. http://dx.doi.org/10.1209/0295-5075/acbf6f.
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Abstract 3He(d,γ)5Li is important in the Big Bang Nucleosynthesis (BBN), as it provides seeds for the 6Li formation. Within the framework of the potential model the 3He(d,γ)5Li is analyzed. In the present investigation the nuclear width , nuclear cross-sections, astrophysical S-factor, and nuclear reaction rates have been computed. The present study is in better agreement with the observed data.
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Boran, S., i E. O. Kahya. "Testing a Dilaton Gravity Model Using Nucleosynthesis". Advances in High Energy Physics 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/282675.
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Big bang nucleosynthesis (BBN) offers one of the most strict evidences for theΛ-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, and7Li) are significantly different for some cases, and a comparison is given between a particular dilaton gravity model andΛ-CDM in the light of the astrophysical observations.
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Gai, M., E. E. Kading, M. Hass, K. M. Nollett, S. R. Stern, Th Stora i A. Weiss. "The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem”". EPJ Web of Conferences 227 (2020): 01007. http://dx.doi.org/10.1051/epjconf/202022701007.
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We report the first measurement of alpha-particles from the interaction of neutrons with 7Be at “temperatures” of Big Bang Nucleosynthesis (BBN). We measured the Maxwellian averaged cross sections (MACS), with neutron beams produced by the LiLiT at the SARAF in Israel (with kT = 49.5 keV hence 0.57 GK). In addition, we measured the cross section of the 7Be(n,p) reaction, which is in excellent agreement with the recent measurement of the n_TOF collaboration, further substantiating our method as a demonstration of “proof of principle”. The cross section for the 7Be(n,ga) and the 7Be(n,a) reaction measured in the “BBN window” is considerably smaller than compiled by Wagoner in 1969 and used today in Big Bang Nucleosynthesis (BBN). We also rule out a hitherto unknown resonance in 8Be at the BBN window, that was conjectured as a possible standard nuclear physics solution to the “Primordial 7Li Problem”. Together with previous results, we deduce a new Wagoner-like Rate for the destruction of 7Be by neutrons which is based on all current measured data. We conclude the lack of a standard nuclear solution to the “Primordial 7Li Problem”. Our upper limit on the cross sections for the high energy alpha-particles is in agreement with recent measurement of the n_TOF collaboration, but it is considerably smaller than the p-wave extrapolation of the Kyoto collaboration. We measured the alpha-particles from the 7Be(n,gi)8Be*(3.03 MeV) reaction, which is considerably larger than a previous s-wave estimate. Hence, in contrast, we conclude s-wave dominance at BBN energies, as would be expected due to the broad (122 keV) low lying 2” state at En = 10 keV.
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Reeves, Hubert. "Concluding Remarks II". Symposium - International Astronomical Union 198 (2000): 578–90. http://dx.doi.org/10.1017/s0074180900167361.
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The symposium has shown that our subject is well and very alive. It is progressing rapidly, thanks to a large amount of new observational data, obtained in particular by a young generation of competent astronomers. It is encouraging, incidentally, to note the large fraction of women in this generation. When I started in this field, some forty years ago, the feminine contribution was much smaller. I plan to review the state of the situation for each of the three nucleosynthesis processes responsible for the light elements: Big Bang Nucleosynthesis (BBN), galactic cosmic ray spallation of interstellar nuclei (GCR) and stellar nucleosynthesis. I will point out their successes, their riddles and possible avenues by which these riddles could be solved. I plan first to review the observations.
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Pizzone, R. G., R. Spartá, M. La Cognata, L. Lamia, C. Spitaleri, C. A. Bertulani i A. Tumino. "Nuclear physics and its role for describing the early universe". International Journal of Modern Physics: Conference Series 49 (styczeń 2019): 1960012. http://dx.doi.org/10.1142/s2010194519600127.
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Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of [Formula: see text], [Formula: see text]He and [Formula: see text]He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN [Formula: see text]. These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the [Formula: see text]He reaction rate were also taken into account.These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed.
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KALITA, S., H. L. DUORAH i K. DUORAH. "BIG BANG NUCLEOSYNTHESIS WITH A CONSTANT VACUUM ENERGY MOTIVATED BY CYCLIC COSMOLOGY". International Journal of Modern Physics A 26, nr 02 (20.01.2011): 331–39. http://dx.doi.org/10.1142/s0217751x11051275.
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Abundances of primordial deuterium, [Formula: see text] and helium, Yp, are examined by modifying the early universe expansion rate and hence the time–temperature relation, including a constant vacuum energy motivated by the cyclic scenario of brane cosmology. Enhancement of abundances with respect to standard BBN prediction is found. Rapid expansion leads to early freeze-out of weak interaction and hence to an enhanced neutron fraction at elevated freeze-out temperature, which in turn results in more helium. Nucleosynthesis at a much lower temperature (due to rapid expansion) faces a larger Coulomb barrier and leaves more deuterium behind, which is also implied by a lower baryon-to-photon ratio (η) as we increase the vacuum energy density. The change in the helium fraction agrees within orders of magnitudes with that found by the effect of more neutrino flavors on Yp. Elevation of the neutron fraction at freeze-out is revealed by decrease in the neutron–proton mass difference (Q) from 1.293 MeV to 1.279 MeV, which is consistent with the study of the influence of extra dimension size on BBN. The lowest Q value corresponds to the highest vacuum energy and also to the largest size of the extra dimension. The upper limit on vacuum energy density is found by estimating the contribution from nonbaryonic dark matter by using X-ray emission from galaxy clusters and taking a flat spatial geometry, which is found to be the cosmological constant (Λ) observed today, so that the abundances do not run beyond the observational upper bounds. The allowed range of ΩΛ, 0.786 ≤ Ω Λ ≤ 0.844, makes Yp and [Formula: see text] lie within the observational upper bounds, which yields a Big Bang equivalence of the Λ universe. This is expected to further motivate the cyclic scenario, which incorporates a small and constant vacuum energy density tied to spacetime.
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LEE, LU-YUN, CHIA-MIN LIN i CHIAN-SHU CHEN. "KINEMATICALLY BLOCKED CURVATON". Modern Physics Letters A 26, nr 36 (30.11.2011): 2731–37. http://dx.doi.org/10.1142/s0217732311037066.
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In this paper, we investigate the idea that the decay of a curvaton is kinematically blocked and show that the coupling constant for curvaton decay can be as large as [Formula: see text]. We also find in this case the lower bound of the Hubble parameter at horizon exit from big bang nucleosynthesis (BBN) is H* ≳ 7.2 × 10-9M P ~ 1010 GeV . Similar to conventional curvaton scenario, the nonlinear parameter can be as large as fNL = 100.
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Sasankan, N., Mayukh R. Gangopadhyay, G. J. Mathews i M. Kusakabe. "Limits on brane-world and particle dark radiation from big bang nucleosynthesis and the CMB". International Journal of Modern Physics E 26, nr 08 (sierpień 2017): 1741007. http://dx.doi.org/10.1142/s0218301317410075.
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The term dark radiation is used both to describe a noninteracting neutrino species and as a correction to the Friedmann Equation in the simplest five-dimensional (5D) RS-II brane-world cosmology. In this paper, we consider the constraints on both the meanings of dark radiation-based upon the newest results for light-element nuclear reaction rates, observed light-element abundances and the power spectrum of the Cosmic Microwave Background (CMB). Adding dark radiation during big bang nucleosynthesis (BBN) alters the Friedmann expansion rate causing the nuclear reactions to freeze out at a different temperature. This changes the final light element abundances at the end of BBN. Its influence on the CMB is to change the effective expansion rate at the surface of the last scattering. We find that the BBN constraint reduces the allowed range for both types of dark radiation at 10[Formula: see text]Mev to between [Formula: see text] and [Formula: see text] of the total background energy density at 10[Formula: see text]Mev. Combining this result with fits to the CMB power spectrum, produces different results for particle versus brane-world dark radiation. In the brane-world, the range decreases from [Formula: see text] to [Formula: see text]. Thus, we find that the ratio of dark radiation to the background total relativistic mass energy density [Formula: see text] is consistent with zero although there remains a very slight preference for a positive (rather than negative) contribution.
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KANG, HO-SHIK. "PRIMORDIAL NUCLEOSYNTHESIS CONSTRAINTS ON NEUTRINO DEGENERACY". International Journal of Modern Physics D 02, nr 04 (grudzień 1993): 381–400. http://dx.doi.org/10.1142/s0218271893000271.
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Based on the work by Kang and Steigman, I review the effects of neutrino degeneracy on big bang nucleosynthesis (BBN). Since the electron-neutrino degeneracy and the non-electron-neutrino degeneracy play a different role in the synthesis of the light elements ( D , 3 He , 4 He , 7 Li ), besides the baryon asymmetry (the nucleon-to-photon ratio; η ≡ nB/nγ) there are two additional free parameters in our scenario of degenerate BBN. An extended range of these parameters has been explored. It is shown that at a given η value, the agreement of the predicted primordial abundances of the light elements with those observationally inferred abundances restricts the permitted range of neutrino degeneracies, particularly the electron-neutrino degeneracy. Furthermore, we find that a large baryon density, even baryon-dominated, critical density (ΩB=1) Universe successfully provides the consistency between the predicted and observed abundances of all the light elements if neutrinos are degenerate enough. For an ΩB=1 Universe, for example, η10=80 is permitted if the electron-neutrino degeneracy and the expansion rate due to the non-electron-neutrino degeneracies fall in the ranges 1.2 ≲ ξνe ≲ 1.5, 17 ≲ S (ξνμ,τ) ≲ 33, respectively.
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Mossa, Viviana. "A BGO set-up for the direct measurement of the D(p,γ)3He fusion cross section at LUNA". Journal of Physics: Conference Series 1668, nr 1 (1.10.2020): 012028. http://dx.doi.org/10.1088/1742-6596/1668/1/012028.
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Abstract The Big Bang Nucleosynthesis (BBN) describes the production of light nuclides occurred during the first minutes of cosmic time. It started with the accumulation of deuterium, whose primordial abundance is sensitive to the universal baryon density and to the amount of relativistic particles. Currently the main source of uncertainty to an accurate theoretical deuterium abundance evaluation is due to the poor knowledge of the D(p, γ)3He cross section at BBN energies. The present work wants to describe one of the two experimental approaches proposed by the LUNA collaboration, whose goal is to measure with unprecedented precision, the reaction cross section in the energy range 30 < Ecm[keV] < 300.
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Benetti, Micol, Salvatore Capozziello i Gaetano Lambiase. "Updating constraints on f(T) teleparallel cosmology and the consistency with big bang nucleosynthesis". Monthly Notices of the Royal Astronomical Society 500, nr 2 (5.11.2020): 1795–805. http://dx.doi.org/10.1093/mnras/staa3368.
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ABSTRACT We focus on viable f(T) teleparallel cosmological models, namely power law, exponential, and square-root exponential, carrying out a detailed study of their evolution at all scales. Indeed, these models were extensively analysed in the light of late time measurements, while it is possible to find only upper limits looking at the very early time behaviour, i.e. satisfying the big bang nucleosynthesis (BBN) data on primordial abundance of 4He. Starting from these indications, we perform our analysis considering both background and linear perturbations evolution and constrain, beyond the standard six cosmological parameters, the free parameters of f(T) models in both cases whether the BBN consistency relation is considered or not. We use a combination of Cosmic Microwave Background, Baryon Acoustic Oscillation, Supernovae Ia and galaxy clustering measurements, and find that very narrow constraints on the free parameters of specific f(T) cosmology can be obtained, beyond any previous precision. While no degeneration is found between the helium fraction, YP, and the free parameter of f(T), we note that these models constrain the current Hubble parameter, H0, higher extent than the standard model one, fully compatible with the Riess et al. measurement in the case of power-law f(T) model. Moreover, the free parameters are constrained at non-zero values in more than 3-σ, showing a preference of the observations for extended gravity models.
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Moscoso, Joseph, Rafael S. de Souza, Alain Coc i Christian Iliadis. "Bayesian Estimation of the D(p,γ)3He Thermonuclear Reaction Rate". Astrophysical Journal 923, nr 1 (1.12.2021): 49. http://dx.doi.org/10.3847/1538-4357/ac1db0.
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Abstract Big bang nucleosynthesis (BBN) is the standard model theory for the production of light nuclides during the early stages of the universe, taking place about 20 minutes after the big bang. Deuterium production, in particular, is highly sensitive to the primordial baryon density and the number of neutrino species, and its abundance serves as a sensitive test for the conditions in the early universe. The comparison of observed deuterium abundances with predicted ones requires reliable knowledge of the relevant thermonuclear reaction rates and their corresponding uncertainties. Recent observations reported the primordial deuterium abundance with percent accuracy, but some theoretical predictions based on BBN are in tension with the measured values because of uncertainties in the cross section of the deuterium-burning reactions. In this work, we analyze the S-factor of the D(p,γ)3He reaction using a hierarchical Bayesian model. We take into account the results of 11 experiments, spanning the period of 1955–2021, more than any other study. We also present results for two different fitting functions, a two-parameter function based on microscopic nuclear theory and a four-parameter polynomial. Our recommended reaction rates have a 2.2% uncertainty at 0.8 GK, which is the temperature most important for deuterium BBN. Differences between our rates and previous results are discussed.
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Park, Jubin, Chae-min Yun, Myung-Ki Cheoun i Dukjae Jang. "Oscillating cosmic evolution and constraints on big bang nucleosynthesis in the extended Starobinsky model". Journal of Cosmology and Astroparticle Physics 2023, nr 05 (1.05.2023): 016. http://dx.doi.org/10.1088/1475-7516/2023/05/016.
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Abstract We investigate the cosmic evolutions in the extended Starobinsky model (eSM) obtained by adding one RabRab term to the Starobinsky model. We discuss the possibility of various cosmic evolutions with a special focus on the radiation-dominated era (RDE). Using simple assumptions, a second-order non-linear differential equation describing the various cosmic evolutions in the eSM is introduced. By solving this non-linear equation numerically, we show that the various cosmic evolutions, such as the standard cosmic evolution (a ∝ t 1/2) and a unique oscillating cosmic evolution, are feasible due to the effects of higher-order terms introduced beyond Einstein's gravity. Furthermore, we consider big bang nucleosynthesis (BBN), which is the most important observational result in the RDE, to constrain the free parameters of the eSM. The primordial abundances of the light elements, such as 4He, D, 3He, 7Li, and 6Li by the cosmic evolutions are compared with the most recent observational data. It turns out that most non-standard cosmic evolutions can not easily satisfy these BBN constraints, but a free parameter of the viable models with the oscillating cosmic evolution is shown to have an upper limit by the constraints. In particular, we find that the free parameter is most sensitive to deuterium and 4He abundances, which are being precisely measured among other elements. Therefore, more accurate measurements in the near future may enable us to distinguish the eSM from the standard model as well as other models.
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Lucia Anna, Damone, N. Colonna, M. Barbagallo, M. Mastromarco, J. Andrzejewski, P. Finocchiaro i L. Cosentino. "7Be(n,p) cross section measurement for the Cosmological Lithium Problem at the n_TOF facility at CERN". EPJ Web of Conferences 184 (2018): 02004. http://dx.doi.org/10.1051/epjconf/201818402004.
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One of the most puzzling problems in Nuclear Astrophysics is the "Cosmological Lithium Problem", i.e the discrepancy between the primordial abundance of 7Li observed in metal poor halo stars [1], and the one predicted by Big Bang Nucleosynthesis (BBN). One of the reactions that could have an impact on the problem is 7Be(n,p)7Li. Despite of the importance of this reaction in BBN, the cross-section has never been directly measured at the energies of interest for BBN. Taking advantage of the innovative features of the second experimental area at the n_TOF facility at CERN, an accurate measurement of 7Be(n,p) cross section has been recently performed at n_TOF, with a pure 7Be target produced by implantation of a 7Be beam at ISOLDE. The experimental procedure, the setup used in the measurement and the results obtained so far will be here presented.
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Cavanna, Francesca. "Probing the early Universe from deep underground". EPJ Web of Conferences 260 (2022): 08005. http://dx.doi.org/10.1051/epjconf/202226008005.
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Big Bang Nucleosynthesis (BBN) occurs during the first minutes of cosmological time in a rapidly expanding hot and dense Universe, where a fraction of protons and nearly all free neutrons end up bound in 4He, while D, 3H, 3He, 6Li, 7Li and 7Be nuclei form in trace quantities. Among these elements, deuterium is an excellent indicator of cosmological parameters because its abundance is highly sensitive to the primordial baryon density and to the number of relativistic species. Although astronomical observations of primordial deuterium abundance have reached percent accuracy, theoretical predictions based on BBN were hampered by large uncertainties on the cross-section of the deuterium burning D(p,γ)3He reaction, before the LUNA measurement. In the following, I will report the results of the experimental campaign carried on at LUNA and its cosmological implications.
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Amin, Mustafa A., Mark P. Hertzberg, David I. Kaiser i Johanna Karouby. "Nonperturbative dynamics of reheating after inflation: A review". International Journal of Modern Physics D 24, nr 01 (28.12.2014): 1530003. http://dx.doi.org/10.1142/s0218271815300037.
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Our understanding of the state of the universe between the end of inflation and big bang nucleosynthesis (BBN) is incomplete. The dynamics at the end of inflation are rich and a potential source of observational signatures. Reheating, the energy transfer between the inflaton and Standard Model fields (possibly through intermediaries) and their subsequent thermalization, can provide clues to how inflation fits in with known high-energy physics. We provide an overview of our current understanding of the nonperturbative, nonlinear dynamics at the end of inflation, some salient features of realistic particle physics models of reheating, and how the universe reaches a thermal state before BBN. In addition, we review the analytical and numerical tools available in the literature to study preheating and reheating and discuss potential observational signatures from this fascinating era.
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Pizzone, R. G., i C. Spampinato. "The long-standing connection of BBN and Indirect measurements: The 3He(n,p)3H reaction at Big Bang energies". EPJ Web of Conferences 279 (2023): 01001. http://dx.doi.org/10.1051/epjconf/202327901001.
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Nuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path which drives the elemental nucleosynthesis in the first twenty minutes of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a hard task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the primordial nucleosynthesis network. In this work we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the 3He(n,p)3H reaction after a detailed study of the 2H(3He,pt)H three–body process. The experiment was performed using the 3He beam, delivered at a total kinetic energy of 9 MeV by the Tandem at the Physics and Astronomy Department of the University of Notre Dame. Data extracted from the present measurement are compared with other published sets available in literature. Astrophysical applications will also be discussed in details.
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Makki, T. R., i M. F. El Eid. "The lithium problem: new insight in the big bang nucleosynthesis (BBN) beyond the standard model". Journal of Physics: Conference Series 869 (czerwiec 2017): 012091. http://dx.doi.org/10.1088/1742-6596/869/1/012091.
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DI BARI, PASQUALE, PAOLO LIPARI i MAURIZIO LUSIGNOLI. "THE νμ↔νs INTERPRETATION OF THE ATMOSPHERIC NEUTRINO DATA AND COSMOLOGICAL CONSTRAINTS". International Journal of Modern Physics A 15, nr 15 (20.06.2000): 2289–328. http://dx.doi.org/10.1142/s0217751x00000951.
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The data on atmospheric neutrinos can be explained assuming the existence of oscillations between νμ's and a light sterile neutrino with mixing close to maximal, and δm2~3×10-3 eV 2. This interpretation of the data is in potential conflict with the successes of big bang nucleosynthesis (BBN), since oscillations can result in a too large contribution of the sterile state to the energy density of the universe at the epoch of nucleosynthesis. The possibility to evade these cosmological constraints has been recently the object of some controversy. In this work we rediscuss this problem and find that the inclusion of a small mixing of the sterile state with ντ can result in the generation of a large lepton asymmetry that strongly suppress the νμ↔νs oscillations eliminating the possible conflict with BBN bounds. In this scheme the mass of the tau neutrino must be larger than few eV's and is compatible with cosmological bounds. Our calculations are performed using a Pauli–Boltzmann method. In this approach it is also possible to develop analytic calculations that allow physical insight in the processes considered and give support to the numerical results.
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Haro Cases, Jaume, i Llibert Aresté Saló. "The Spectrum of Gravitational Waves, Their Overproduction in Quintessential Inflation and Its Influence in the Reheating Temperature". Universe 6, nr 6 (23.06.2020): 87. http://dx.doi.org/10.3390/universe6060087.
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One of the most important issues in an inflationary theory as standard or quintessential inflation is the mechanism to reheat the universe after the end of the inflationary period in order to match with the Hot Big Bang universe. In quintessential inflation two mechanisms are frequently used, namely the reheating via gravitational particle production which is, as we will see, very efficient when the phase transition from the end of inflation to a kinetic regime (all the energy of the inflaton field is kinetic) is very abrupt, and the so-called instant preheating which is used for a very smooth phase transition because in that case the gravitational particle production is very inefficient. In the present work, a detailed study of these mechanisms is done, obtaining bounds for the reheating temperature and the range of the parameters involved in each reheating mechanism in order that the Gravitational Waves (GWs) produced at the beginning of kination do not disturb the Big Bang Nucleosynthesis (BBN) success.
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Chichiri, Carlos, Graciela B. Gelmini, Philip Lu i Volodymyr Takhistov. "Cosmological dependence of sterile neutrino dark matter with self-interacting neutrinos". Journal of Cosmology and Astroparticle Physics 2022, nr 09 (1.09.2022): 036. http://dx.doi.org/10.1088/1475-7516/2022/09/036.
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Abstract Unexplored interactions of neutrinos could be the key to understanding the nature of the dark matter (DM). In particular, active neutrinos with new self-interactions can produce keV-mass sterile neutrinos that account for the whole of the DM through the Dodelson-Widrow mechanism for a large range of active-sterile mixing values. This production typically occurs before Big-Bang Nucleosynthesis (BBN) in a yet uncharted era of the Universe. We assess how the mixing range for keV-mass sterile neutrino DM is affected by the uncertainty in the early Universe pre-BBN cosmology. This is particularly relevant for identifying the viable parameter space of sterile neutrino searches allowed by all astrophysical limits, as well as for cosmology, since the detection of a sterile neutrino could constitute the first observation of a particle providing information about the pre-BBN epoch. We find that the combined uncertainties in the early Universe cosmology and neutrino interactions significantly expand the allowed parameter space for sterile neutrinos that can constitute the whole of the DM.
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Yeh, Tsung-Han, Jessie Shelton, Keith A. Olive i Brian D. Fields. "Probing physics beyond the standard model: limits from BBN and the CMB independently and combined". Journal of Cosmology and Astroparticle Physics 2022, nr 10 (1.10.2022): 046. http://dx.doi.org/10.1088/1475-7516/2022/10/046.
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Abstract We present new Big Bang Nucleosynthesis (BBN) limits on the cosmic expansion rate or relativistic energy density, quantified via the number Nν of equivalent neutrino species. We use the latest light element observations, neutron mean lifetime, and update our evaluation for the nuclear rates d + d ⟶ 3He + n and d + d ⟶ 3H+ p. Combining this result with the independent constraints from the cosmic microwave background (CMB) yields tight limits on new physics that perturbs Nν and η prior to cosmic nucleosynthesis: a joint BBN+CMB analysis gives Nν = 2.898 ± 0.141, resulting in Nν < 3.180 at 2σ. We apply these limits to a wide variety of new physics scenarios including right-handed neutrinos, dark radiation, and a stochastic gravitational wave background. The strength of the independent BBN and CMB constraints now opens a new window: we can search for limits on potential changes in Nν and/or the baryon-to-photon ratio η between the two epochs. The present data place strong constraints on the allowed changes in Nν between BBN and CMB decoupling; for example, we find -0.708 < Nν CMB - Nν BBN < 0.328 in the case where η and the primordial helium mass fraction Yp are unchanged between the two epochs; we also give limits on the allowed variations in η or in (η, Nν ) jointly. We discuss scenarios in which such changes could occur, and show that BBN+CMB results combine to place important constraints on some early dark energy models to explain the H0 tension. Looking to the future, we forecast the tightened precision for Nν arising from both CMB Stage 4 measurements as well as improvements in astronomical 4He measurements. We find that CMB-S4 combined with present BBN and light element observation precision can give σ(Nν ) ≃ 0.03. Such future precision would reveal the expected effect of neutrino heating (Neff -3 = 0.044) of the CMB during BBN, and would be near the level to reveal any particle species ever in thermal equilibrium with the standard model. Improved Yp measurements can push this precision even further.
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Mathews, Grant, Motohiko Kusakabe, Mayukh Gangopadhyay, Toshitaka Kajino i Nishanth Sasankan. "Primordial Nucleosynthesis: Constraints on the Birth of the Universe". EPJ Web of Conferences 184 (2018): 01011. http://dx.doi.org/10.1051/epjconf/201818401011.
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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.
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KIRILOVA, DANIELA. "NEUTRINO SPECTRUM DISTORTION DUE TO OSCILLATIONS AND ITS BBN EFFECT". International Journal of Modern Physics D 13, nr 05 (maj 2004): 831–41. http://dx.doi.org/10.1142/s0218271804004906.
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We study the distortion of electron neutrino energy spectrum due to oscillations with the sterile neutrino νe↔νs, for different initial populations of the sterile state δNs at the onset of oscillations. The influence of this spectrum distortion on Big Bang Nucleosynthesis is analyzed. Only the case of an initially empty sterile state was studied in previous publications. The primordial abundance of 4He is calculated for all possible δNs:0≤δNs≤1 in the model of oscillations, effective after electron neutrino decoupling, for which the spectrum distortion effects on the neutron–proton transitions are the strongest. It is found that the spectrum distortion effect may be dominant, not only in the case of small δNs, but also in the case of large initial population of νs. For example, in the resonant case it may play a considerable role even for very large δNs~0.8. Cosmological constraints on neutrino mixing for small δNs are discussed.
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KIRILOVA, DANIELA. "BBN CONSTRAINTS ON NEUTRINO OSCILLATIONS PARAMETERS RELAXED OR STRENGTHENED". International Journal of Modern Physics D 16, nr 07 (lipiec 2007): 1197–210. http://dx.doi.org/10.1142/s0218271807010791.
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Big Bang Nucleosynthesis (BBN) with nonequilibrium νe ↔ νs oscillations, in the more general case of non-zero population of νs before oscillations δNs ≠ 0, is discussed. 4 He primordial production Yp(δNs) in the presence of νe ↔ νs oscillations for different initial populations of the sterile neutrino state 0 ≤ δ Ns ≤ 1 and the full range of oscillation parameters is calculated. Non-zero δNs has a two-fold effect on 4 He : (i) it enhances the energy density and hence increases the cosmic expansion rate, leading to Ypoverproduction, and (ii) it suppresses the kinetic effects of oscillations on BBN, namely, the effects on pre-BBN nucleon kinetics, caused by the νe energy spectrum distortion and the [Formula: see text] asymmetry generation by oscillations, leading to decreased Yp production. Depending on oscillation parameters one or the other effect may dominate, causing, correspondingly, either a relaxation of the cosmological constraints or their strengthening with the increase of δNs. More general BBN constraints on νe ↔ νs oscillation parameters, corresponding to 3% Yp overproduction, for different initial populations of the sterile state are calculated. Previous BBN constraints were derived assuming empty sterile state before oscillations. It is shown that the cosmological constraints strengthen with the increase of δNs value, the change being more considerable for nonresonant oscillations.
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Yang, X. J., i Aigen Li. "Deuterated Polycyclic Aromatic Hydrocarbons in the Interstellar Medium: The Aliphatic C–D Band Strengths". Astrophysical Journal Supplement Series 268, nr 1 (23.08.2023): 12. http://dx.doi.org/10.3847/1538-4365/ace4c6.
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Abstract Deuterium (D) was exclusively generated in the Big Bang, and the standard Big Bang nucleosynthesis (BBN) model predicts a primordial abundance of D/H ≈ 26 parts per million (ppm). As the Galaxy evolves, D/H gradually decreases because of astration. The Galactic chemical evolution (GCE) model predicts a present-day abundance of D/H ≳ 20 ppm. However, observations of the local interstellar medium have revealed that the gas-phase interstellar D/H varies considerably from one region to another and has a median abundance of D/H ≈ 13 ppm, substantially lower than predicted from the BBN and GCE models. It has been suggested that the missing D atoms of D/H ≈ 7 ppm could have been locked up in deuterated polycyclic aromatic hydrocarbon (PAH) molecules. However, we have previously demonstrated that PAHs with aromatic C–D units are insufficient to account for the missing D. Here we explore if PAHs with aliphatic C–D units could be a reservoir of D. We perform quantum chemical computations of the vibrational spectra of superdeuterated PAHs (in which one D and one H share one C atom) and PAHs to which a D-substituted methyl group is attached, and derive the band strengths of the aliphatic C–D stretch (A 4.65). By applying the computationally derived A 4.65 to the observed aliphatic C–D emission at ∼4.6–4.8 μm, we find that PAHs with aliphatic C–D units could have tied up a substantial amount of D/H and marginally account for the missing D. The possible routes for generating PAHs with aliphatic C–D units are also discussed.
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Zhou, Yi. "Methods of Discovering New Physics from the Cosmic Neutrino Background". Journal of Physics: Conference Series 2381, nr 1 (1.12.2022): 012079. http://dx.doi.org/10.1088/1742-6596/2381/1/012079.
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Abstract Neutrinos play a significant role in the thermal history of the early universe. The standard cosmological model predicts a relic sea of neutrinos, often referred to as the Cosmic Neutrino Background (CNB). The effects of CNB are parameterized as the effective number of neutrino flavors N eff, which could be measured by indirect astronomy observations. The numerical calculations of the neutrino decoupling process give a result of N eff = 3.046. To measure it with astronomy observations, the primordial abundance of elements from the Big Bang Nucleosynthesis (BBN) and the anisotropies in the distribution of the Cosmic Microwave Background (CMB) are investigated. The observation results basically match the prediction. Direct detection methods are also proposed via capturing neutrinos on a tritium target, which could be practical assuming a large-neutrino-mass cosmological model.
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Kantha, L. "A Time-DependentΛandGCosmological Model Consistent with Cosmological Constraints". Advances in Astronomy 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/9743970.
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The prevailing constantΛ-Gcosmological model agrees with observational evidence including the observed red shift, Big Bang Nucleosynthesis (BBN), and the current rate of acceleration. It assumes that matter contributes 27% to the current density of the universe, with the rest (73%) coming from dark energy represented by the Einstein cosmological parameterΛin the governing Friedmann-Robertson-Walker equations, derived from Einstein’s equations of general relativity. However, the principal problem is the extremely small value of the cosmological parameter (~10−52 m2). Moreover, the dark energy density represented byΛis presumed to have remained unchanged as the universe expanded by 26 orders of magnitude. Attempts to overcome this deficiency often invoke a variableΛ-Gmodel. Cosmic constraints from action principles require that either bothGandΛremain time-invariant or both vary in time. Here, we propose a variableΛ-Gcosmological model consistent with the latest red shift data, the current acceleration rate, and BBN, provided the split between matter and dark energy is 18% and 82%.Λdecreases (Λ~τ-2, whereτis the normalized cosmic time) andGincreases (G~τn) with cosmic time. The model results depend only on the chosen value ofΛat present and in the far future and not directly onG.