Hot big bang

At present, the most widely accepted theory for the origin and evolution of the universe to its present form is the hot big bang . > It is supposed that all the matter in the universe... 

Hot big-bang theory of expanding universe includes an (incorrect) theory of nucleogenesis... 

The Hot Big Bang theory of the Universe was pioneered by George Gamow, R. A. Alpher and R. C. Herman in the late 1940s and early 50s. They supposed that during the first few minutes of the (then radiation-dominated) Universe, matter was originally present in the form of neutrons and that, after some free decay, protons captured neutrons and successive captures, followed by /3-decays, built up all the elements (Alpher Herman 1950). 

The basic assertion of the Hot Big Bang theory is that, as one goes back to early times, one encounters almost unlimited high temperatures and densities. The basic evidence for this is threefold ... 

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. 

We will begin by briefly reviewing the General Cosmological Framework in which the following lectures will fit the Hot Big Bang ... 

In the late seventies, the history of the early Universe was described with the help of the hot Big-Bang scenario the universe originated from an initial singularity and had then expanded, being filled by radiation and subsequently by non relativistic matter (baryon and Dark Matter). 

We shall first review the (well-known) problems of the hot Big-Bang scenario in the next section. The we shall do a presentation of the inflationary mechanism, where we shall also introduce some important quantities the slow roll parameters (Section 7.3). In order to understand properly how inflation can seed density perturbations in the Universe, we shall then make an introduction to the problem of density perturbation in cosmology (Section 7.4). We shall then adapt this formalism to the inflationary situation where the Universe experiences a quasi-exponential expansion under the influence of a single scalar field (Section 7.5). The seeds for the cosmological perturbations (i.e. what we have to take as initial conditions when solving the perturbation equations are in fact the quantum fluctuations of this scalar field. We shall make a very brief introduction to this subject in Section 7.6. With all these tools we shall then compute the final spectrum (i.e., long after inflation) of the cosmological perturbations in Section 7.7. 

GUT scale ( 1015 eV). So again, the standard hot Big-Bang scenario fails to explain why these unwanted relics do not exist4. 

Maybe the most annoying problem of the hot Big-Bang scenario is that it does not provide any explanation for the existence of structures in the Universe. It is well-known that structures can form through the Jeans instability only in a matter dominated era. However since the matter domination occurred quite recently in the history of the universe (around z 104, see Eq. (7.29)), one is forced to suppose that small density fluctuations already existed before that epoch. Since no efficient process is known to form density perturbations in a radiation-dominated universe, so one has to suppose that the seeds for the astrophysical objects we observe were part of the initial condition of the whole scenario. As we shall now see, the biggest success of inflation is to provide a simple explanation for the presence of such density perturbations, in addition to solving quite naturally the other problems. 

When the above four basic observational facts are combined and considered together, there is no escape from the conclusion that our universe is expanding and cooling. This conclusion is entirely consistent with the Hot Big Bang model. Sometimes, we hear the stronger statement that these observations prove that there was a Hot Big Bang. However, the scientific method does not truly produce proofs in the mathematical sense. 

Department of Applied Mathematics and Theoretical Physics. University of Cambridge. The Hot Big Bang Model. Available online. URL http //www.solarviews.com/eng/asteroid.htm. Accessed on November 1, 2006. 

Big bang nucleosynthesis (BBN), describes the production of the light elements in the early universe. The theoretical prediction for the abundances of D, He, He, and Li is discussed and compared with their observational determination. The spectrum of anisotropies in the cosmic microwave backgroimd (CMB) now independently measures the baryon density to high precision. As a result, the CMB data test BBN. One finds that the CMB along with D and He observations paint a consistent picture. This concordance stands as a major success of the hot big bang. On the other hand, Li remains discrepant with the CMB-preferred baryon density possible explanations are reviewed. 

To summarize In order to support the big bang, the observation of heavy metals in the very early universe needs to be explained. These elements can only be produced in stars. Suitably parametrized simulations identify a certain class of VMS s, if they exist, as a possible source of metal enrichment to match observation. Therefore VMS s existed in the early universe The only remaining problem is that the temperature of the hot big bang is too high for clumping to occur within the primordial dark matter without a suitable coolant. Voila Primordial molecular hydrogen could do the job, provided it is destroyed again before it disrupts post-inflation events. 

It is constructive to examine what this science consists of. As before, it starts with the assumption of a hot big bang, now interpreted to produce, not only space and time, but also all of the matter (as primordial molecular hydrogen) and energy observed in the universe today, as well as an excessive amount of non-baryonic cold dark matter and inflationary energy . 

Our galaxy is probably 13.7 0.2 Gyr old and was formed by the hot Big Bang, assuming that the whole mass of the galaxy was concentrated in a primordial core. Based on the principles of physics, it is assumed that density and temperature were... 

Khoury J, Ovmt BA, Steinhardt PJ, Turok N (2001) Ekpyrotic universe colliding branes and the origin of the hot big bang. Phys Rev D 64 123522-123523... 

When the universe was only a few minutes old, the temperature and density were high enough for nuclear fusion reaction to take place (Fig. 8.3). The formation of elements and isotopes, such as deuterium, isotopes of He, lithium, beryllium and boron, the Big Bang nucleosynthesis, is another indication for a hot Big Bang. The Big Bang theory predicts that in the early universe 24% He was produced. This was in the form of the stable He isotope (there are several reviews on that topic e.g. Olive, 1999 [253]). It is interesting to note that the production of this element is not strongly dependent on the density of matter in the universe. By density we mean here the value for the today s universe. Between the interval of density of matter from 10 to 10 kgm the " He abundance remains very close to the value of 24%. 

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