Early universe

The astrochemistty of ions may be divided into topics of interstellar clouds, stellar atmospheres, planetary atmospheres and comets. There are many areas of astrophysics (stars, planetary nebulae, novae, supemovae) where highly ionized species are important, but beyond the scope of ion chemistry . (Still, molecules, including H2O, are observed in solar spectra [155] and a surprise in the study of Supernova 1987A was the identification of molecular species, CO, SiO and possibly ITf[156. 157]. ) In the early universe, after expansion had cooled matter to the point that molecules could fonn, the small fraction of positive and negative ions that remained was crucial to the fomiation of molecules, for example [156]... 

Astrophysicists believe that the early universe was composed mostly of hydrogen. As a cloud of hydrogen collapses, heating breaks its hydrogen atoms into a plasma of protons and electrons. A first-generation star forms... 

Massive stars play an important role in numerous astrophysical contexts that range from the understanding of starburst environments to the chemical evolution in the early Universe. It is therefore crucial that their evolution be fully and consistently understood. A variety of observations of hot stars reveal discrepancies with the standard evolutionary models (see [1] for review) He and N excesses have been observed in O and B main sequence stars and large depletions of B accompanied by N enhancements are seen in B stars and A-F supergiants [2,3,4,5], All of these suggest the presence of excess-mixing, and have led to the development of a new generation of evolutionary models which incorporate rotation (full reviews in [1], [6], [7]). 

In the next section each light nuclide is considered in turn, its post-BBN evolution briefly reviewed along with identification of a few of the potential challenges to accurately inferring the primordial abundances from the observational data. Then, having established that the current data - taken at face value - are not entirely consistent with SBBN, I investigate whether changes in the early universe expansion rate can reconcile them. 

There are many different extensions of the standard model of particle physics which result in modifications of the early universe expansion rate (the time -temperature relation). For example, additional particles will increase the energy density (at fixed temperature), resulting in a faster expansion. In such situations it is convenient to relate the extra energy density to that which would have been contributed by an additional neutrino with the ordinary weak interactions [19]. Just prior to e annihilation, this may be written as... 

Study the formation of galaxies in the early universe and their subsequent evolution. 

The matter that made up the solar nebula from which the solar system was formed already was the product of stellar birth, aging and death, yet the Sun is 4.5 billion years old and will perhaps live to be 8 billion years but the Universe is thought to be 15 billion years old (15 Gyr) suggesting that perhaps we are only in the second cycle of star evolution. It is possible, however, that the massive clouds of H atoms, formed in the close proximity of the early Universe, rapidly formed super-heavy stars that had much shorter lifetimes and entered the supernova phase quickly. Too much speculation becomes worrying but the presence of different elements in stars and the subsequent understanding of stellar evolution is supported by the observations of atomic and molecular spectra within the light coming from the photosphere of stars. 

It led to a prediction that the number of different sorts of neutrino (equivalent in standard particle physics to the number of families of quarks and leptons) is less than 4 and probably no more than 3. This prediction was subsequently confirmed (subject to slight reservations about differences between effective numbers of neutrino species in the laboratory and in the early Universe) by measurements of the width or lifetime of the Z° boson at CERN in 1990. 

A large measure of thermal equilibrium in the early Universe, which implies, roughly speaking, that particles and antiparticles with me2 < kTy are present in comparable numbers to photons, whereas when kTy falls below me2, they annihilate and exist only in trace quantities. 

S. Weinberg, Gravitation and Cosmology, Wiley 1972, in E. W. Kolb and M. S. Turner, The Early Universe, Addison-Wesley Press 1990, and in the comprehensive introduction to modern cosmology... 

G. Gamow, R. Alpher and R. Herman develop Hot Big Bang theory and suggest all elements created by neutron captures in early Universe. W. Baade distinguishes two stellar populations. 

The question for the equation of state of strongly interacting matter is a link between many-particle physics and astrophysics/cosmology. Calculated by means of statistical quantum field theory, it serves as a necessary input, e. g., in models of the early universe, or in the context considered here, it determines the structure of stars. 

The beginning of nuclear evolution, launched in the Big Bang, the creation of matter, the emergence of nucleons and the construction of the first nuclei hydrogen, deuterium, helium and lithium that took place in its immediate wake, followed by formation of the first stars in the early Universe and the establishment of stellar nucleosynthesis leading to production of carbon and all the other elements. 

The early Universe can be reasonably described as a dilute gas of particles and radiation in thermal equilibrium, uniquely characterised by its instantaneous density and temperature. The expansion of space causes further dilution and coohng of this gas. 

Kolb E. Turner M.S. (1990) The Early Universe (Addison-Wesley, New York). 

Once the primary isotopes had built up in abundance, then the full range of reactions discussed above became available and nuclides such as C, N, O, O, F, Ne, Ne, 25Mg, 26Mg, and so on, were produced by reactions between primary isotopes and protons and neutrons. Isotopes that require the presence of metals in the initial composition of the star in order to be efficiently synthesized are secondary isotopes. Abundances of primary isotopes built up rapidly in the early universe via synthesis in massive stars. Secondary isotopes initially built up more slowly, but their rate of synthesis increased as metallicity increased. 

For simplicity, we consider the universe to be radiation dominated. This is because the particles, even the highly massive X, Y, and V particles have such large kinetic energies that they behave similar to photons or massless bosons. This state of affairs in the early universe was know to exist up until the universe dropped to a temperature below 103 K 100,000 years into its evolution. For the radiation dominated period in the evolution of the universe the pressure and density were related by... 

Here M is the mass of the particles in the universe. We then see that the universe exhibits a scale change a = R(t + At) /R(t), where At is the duration of the inflationary period. The parameter for the geometry of the spacial universe is O = p/pc, for pc = (R/R)3/SnG. For the condition for flatness O 1 in the early universe, we require that a > 1027. The expansion parameter will reduce go 1 by a factor of a, and thus guarantee that there is cosmic flatness, or close to flatness. 

It is apparent that the numbers and masses of the flavor and quark-lepton transforming gauge bosons are larger than those of the SU(5) minimal model. This means that the value of a is lower, and assuming that the duration of the inflationary period is fixed, the scale for the expansion of the universe is reduced. This means that there is the enhanced prospect for deviations from flatness. So one may presume that the universe started as a small 3-sphere with a large curvature, where the inflationary period flattened out the universe, but maybe not completely. This leaves open the prospect that if before inflation that if the universe were open or closed, k = 1, that the universe today still contains this structure on a sufficiently large scale. The closer to flatness the universe is, the tighter are the constraints on the masses of particles in the early universe. 

The molecules found to date are composed of the elements H, C, N, O, Si, S, and Cl with the bulk of the molecules containing H, C, N, and O. The light elements H, D, and He are of cosmological origin and are therefore tracers of the early universe. On the other hand the heavier elements C, N, O,... are produced in stars by the processes of stellar nucleosynthesis. In addition to the most abundant isotopic forms many stable isotopes such as D, 13C, 170, lsO, 15N, 30Si, 33S, and 34S have been detected (see Appendix 1). The detailed determination of isotopic ratios — though often beset with formidable difficulties — has become a useful indicator of the chemical evolution of molecular clouds and the past chemical history of the galaxy. 

It is presently thought that the early universe was mostly energy with very little matter. Today, our universe is dominated by matter. It is the hope of chemists and physicists to be able to account for and track all the different forms of energy present in a given system along with the mass in order to better understand the chemical and physical processes that occur in our universe. 

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