Big-bang synthesis

There is good agreement between observations and the predictions of Big Bang synthesis. The abundances of H, 4He, 3He, and deuterium, match the predictions very well. For 7Li, observations and predictions match within about a factor of two. It is likely that the main uncertainty for 7Li is in the nuclear physics of its synthesis. This level of agreement represents an impressive success of modem cosmology. 

In support of this conjecture it is noted that the known stable nuclides divide into four modular series of mass number, A(mod4), each of which can be reconstructed by the addition of a-particles (Z/N = 1), starting from the neutron and antineutron combinations, n,nn, n, n n [62]. The scheme, like big-bang synthesis, depends on the availability of the light nuclides 2H and 4He. Unlike big-bang synthesis, all nuclides are proposed to be formed here in one equilibrium process, the only mechanism that explains periodic abundance. 

The extravagent claim that only big-bang synthesis can account for the relative abundances of H and He is based on a chain of assumptions, long enough to predict any desired result. The logic of the (a — / — 7) scheme depends on the assumed relationship between black-body temperature and the radius of the expanding universe... 

The synthesis of the light elements hydrogen, helium and lithium (including their isotopes), which occurred just after the big bang ... 

Table 2.2 lists the most important syntheses occurring in the stars. The main products include the bioelements C, O, N and S. The synthesis of the elements began in the initial phase after the big bang, with that of the proton and the helium nucleus. These continue to be formed in the further development of the stars. The stable nuclide 4He was the starting material for subsequent nuclear syntheses. Carbon-12 can be formed in a triple a-process, i.e., one in which three helium... 

F. Hoyle and R. J. Tayler point out significance of additional neutrinos for helium synthesis in the Big Bang model. 

Big Bang nucleosynthesis is responsible for the synthesis of hydrogen and helium and some of the 7Li. (Stellar nucleosynthesis in main sequence stars transforms about 7% of the hydrogen into 4He.) However, neither stellar nucleosynthesis or Big Bang nucleosynthesis can produce the observed abundances of Li, Be, and B. Consequently, the abundances of Li, Be, and B are suppressed by a factor of 106 relative to the abundances of the neighboring elements (Fig. 12.2). 

The mechanism assumed here is equivalent to the previous proposal [62] of a-addition, with the added advantage of demonstrating the transition between two states defined by Z/N = 1 and r respectively. This proposed synthesis of elements is more economical than the widely accepted big-bang scenario that requires special hypothetical conditions for the production of... 

In the first chapter of this book, deuterium was identified as having originated moments after the big bang thus, deuterium is primordial in character. This raises an important question Can the currently observed amount of deuterium in the universe become another empirical check on big bang cosmology More specifically, can the nuclear synthesis of the light elements—mostly helium ( He) plus mere traces of deuterium ( H), hehum ( He), and lithium ( Li)— which occurred over a brief period soon after the big bang itself, account for their currently observed abundances ... 

Are there processes in namre that destroy deuterium For certain, any deuterium that was part of a cloud that condensed to form a star would be depleted. Stars fuse hydrogen. There are other processes, though rare, that work to take deuterium out of circulation. Their effect would lead to slight reductions in the observed amount of deuterium. So how does the predicted abundance of deuterium compare with its actual abundance when the universe came out of the period of nuclear synthesis 1,000 seconds after the big bang itself ... 

Cosmological nucleosynthesis studies predict that the conditions characterizing the Big Bang are consistent with the synthesis only of the lightest elements H, H, He, " He, and Li (Buries et al., 2001 Cyburt et al., 2002). These contributions define the primordial compositions both of galaxies and of the first stars formed therein. 

Nuclear Astrophysics is the field concerning the synthesis and Evolution of atomic nuclei, by thermonuclear reactions, from the Big Bang to the present. What is the origin of the matter of which we are made [1]. Our high entropy universe resulting from the Big Bang, contains many more photons per particle... 

Where did the carbon come from The universe is primarily composed of hydrogen, with lesser amounts of helium, and comparatively little of the heavier elements (which are collectively termed metals by astronomers). The synthesis of elements from the primordial hydrogen, which was formed from the fundamental particles upon the initial stages of cooling after the Big Bang some 15 Gyr ago, is accomplished by nuclear fusion, which requires the high temperatures and pressures within the cores of stars. Our Sun is relatively small in stellar terms, with a mass of c.2 X 1030kg, and is... 

Fundamental to the existence of a carbon chemistry then is the synthesis and dispersal of carbon by stars. Recent cosmological simulations indicate that the formation of the first stars (so called population III or zero metallicity stars) may have occurred as early as 200 million years after the big bang (8). These very... 

A central, but elusive aim of nuclear research for almost a century has been the understanding of nuclear synthesis, particularly in the hands of astrophysicists. The dearth of experimental data to drive such enquiry has often resulted in the bending of synthesis theory to follow current thinking in cosmogony, rather than the other way around. This situation has not changed materially since the publication of two comprehensive reviews of the problem in 1950, after the decline of Lemaitre s, but before the advent of Gamow s big-bang theories. This period provided an opportunity to consider rival theories without prejudice. 

The final conclusion is clear Uniform correlation between nuclear stability and abundance cannot result from nucleogenesis in a large number of unrelated processes under a variety of reaction conditions, as required by the big-bang mechanism. The suggested alternative of nuclear synthesis by an equilibrium process of systematic a-addition points at a completely different cosmological model and to the direction which this enquiry must follow, while remaining consistent with physical theory. 

Because there are no stable nuclides with H = 5 or 8, the claim was later toned down, for lack of time, to the big-bang production of only the six light nuclei as above. The synthesis of heavier nuclides is postponed to happen in stars at a more leisurely rate. We note that in a black hole, where the radial coordinate turns into a time coordinate there is more than sufficient time to establish the proposed equilibrium. 

The fact that the light nuclides, especially H and He, are more abundant by orders of magnitude, compared to all heavier nuclides, is interpreted to distinguish two fundamentally different modes of synthesis. The big bang is postulated responsible for primordial synthesis of the light nuclei and stellar nucleosynthesis (Burbidge et al., 1957) to produce all the heavy nuclides. 

The near-equality of cosmic and solar abundancies of the chemical elements points at either a single synthesis event, starting from elementary matter, or a common mechanism of nucleogenesis, wherever it happens. The first possibility is the one originally preferred in big-bang cosmology, but later abandoned as there was considered not to be enough time available for this process in the early universe. 

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