Cooking up the first light elements An article by Achim Weiss Contents The big bang models - the cosmological models based on general relativity - tell us that the early universe was extremely hot and dense.
It is now known that the elements observed in the Universe were created in either of two ways. Light elements namely deuterium, helium, and lithium were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe.
Both theory and observation lead astronomers to believe this to be the case. Burbidge, Fowler, and Hoyle.
The BBFH theory, as it came to be known, postulated that all the elements were produced either in stellar interiors or during supernova explosions.
While this theory achieved relative success, it Temperature big bang nucleosynthesis discovered to be lacking in some important respects. To begin with, it was estimated that only a small amount of matter found in the Universe should consist of helium if stellar nuclear reactions were its only source of production.
A similar enigma exists for the deuterium. According to stellar theory, deuterium cannot be produced in stellar interiors; actually, deuterium is destroyed inside of stars. Hence, the BBFH hypothesis could not by itself adequately explain the observed abundances of helium and deuterium in the Universe.
Thanks to the pioneering efforts of George Gamow and his collaborators, there now exists a satisfactory theory as to the production of light elements in the early Universe. In the very early Universe the temperature was so great that all matter was fully ionized and dissociated.
At this temperature, nucleosynthesis, or the production of light elements, could take place. In a short time interval, protons and neutrons collided to produce deuterium one proton bound to one neutron. Most of the deuterium then collided with other protons and neutrons to produce helium and a small amount of tritium one proton and two neutrons.
Lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei. It also predicts about 0. The important point is that the prediction depends critically on the density of baryons ie neutrons and protons at the time of nucleosynthesis. Furthermore, one value of this baryon density can explain all the abundances at once.
In terms of the present day critical density of matter, the required density of baryons is a few percent the exact value depends on the assumed value of the Hubble constant.
This relatively low value means that not all of the dark matter can be baryonic, ie we are forced to consider more exotic particle candidates.
This is one of the corner-stones of the Hot Big Bang model. Further support comes from the consistency of the other light element abundances for one particular baryon density and an independent measurement of the baryon density from the anisotropies in the cosmic microwave background radiation.
It seems like we really understand the physical processes which went on in the first few minutes of the evolution of the Universe! Further details can be found here.The cosmic neutrino background (CNB, CνB) is the universe's background particle radiation composed of neutrinos.
They are sometimes known as relic neutrinos. The CνB is a relic of the big bang ; while the cosmic microwave background radiation (CMB) dates from when the universe was , years old, the CνB decoupled (separated) from matter.
hot Big Bang came with the discovery of the cosmic microwave background (CMB) predictions of the Big Bang nucleosynthesis and the pre-galactic abundances of the temperature and density much higher than the present ones.
These models were. Big Bang Nucleosynthesis leads to some of the most successful predictions derived from the big bang models: The physics of the expanding universe at cosmic .
Theory of Big Bang Nucleosynthesis The relative abundances of the lightest elements (hydrogen, deuterium, helium-3 and helium-4, and some lithium and beryllium) provide a strong test of . Roughly three minutes after the Big Bang itself, the temperature of the Universe rapidly cooled from its phenomenal 10^32 Kelvin to approximately 10^9 Kelvin.
At this temperature, nucleosynthesis, or the production of light elements, could take place. We consider electromagnetic corrections at finite temperature and their effect on the nucleosynthesis in the standard Big Bang scenario.
This requires discussing the finite, temperature dependent correction to the neutron-proton mass difference as well as making use of a previous result on the temperature correction to the mass of the electron.