Embedded Files
Scientists are not sure how matter formed in the first place. Matter appeared after inflation (10-34 sec) and before 10-12 second, but connecting the dots during the first trillionth of a second has been a particularly challenging task. The most popular hypothesis is that the decay of inflaton produced photons, and that photons collided and formed quarks. The problem with this scenario is that when photons collide, they produce equal numbers of matter and antimatter pairs such as quarks and antiquarks. If this was the case, then the matter and antimatter pairs should have eventually annihilated each other, resulting in no matter or antimatter in the universe.
One hypothesis has been that supersymmetry resulted in an excess of matter over antimatter; however, recent supercollider experiments have not supported the existence of supersymmetry. Without supersymmetry, the solution to matter creation is constrained to finely tuned solutions.[1] An example is leptogenesis. which is based on the the possible preference of formation of matter neutrinos over antimatter neutrinos. The leptogenesis theory assumes that there was no Higgs field in the extremely hot early universe, which means that the laws of physics would have been different. Leptogenesis has four key components listed below.
1. Heavy right-handed neutrinos exist. The theoretical heavy right-handed neutrinos would derive mass from something other than the Higgs field.
2. Matter and antimatter neutrinos are the same.
3. Matter neutrinos decay more often to antimatter neutrinos than vice-versa, thus resulting in excess of antimatter neutrinos and thus violating the balance of matter and antimatter.
4. Antimatter leptons formed matter baryons (quarks). In a cooling universe, the Higgs field eventually would appear and give the matter baryons their mass.
In order to test point 3, the Department of Energy Fermilab is building instruments to shoot matter and antimatter neutrinos from Illinois to South Dakota, where the Dune detector located in a deep mine, which will determine if there is a preference for the decay to antimatter neutrinos over matter neutrinos.
Regardless of how matter formed or first appeared in the universe, scientists have been able to simulate the processes that took place after a trillionth of a second (10-12 seconds). Figure 2‑19 shows the progression of temperature (T) and matter formation in the universe.
Figure 2‑19. Particle history of the universe, Credit DOE LBNL.
The temperature at 10-10 seconds was 1015 K (degrees), and at 10-5 seconds was 1012 K. In this interval, it was too hot for the formation of protons. There were just quarks, gluons, photons, electrons, and other particles. This was the quark epoch, during which the state of matter was a quark-gluon plasma. Plasma is a state of matter when electrons are not connected to the atomic nucleus. Scientists were able to simulate the quark-gluon plasma in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. They simulated this plasma by crashing lead and gold nuclei into each other and thus recreating the effect of the immense temperatures in the first millionth of a second.
Figure 2‑20. Formation of hadrons (protons and neutrons) from three quarks and gluon force particles. Credit: Brookhaven National Laboratory.
In the next interval between 10-5 and 10-2 seconds, the universe cooled to the point that protons and neutrons formed. This period is the hadron era (Figure 2-20). At the beginning of the hadron era, the universe formed equal numbers of protons and neutrons, and protons became neutrons, and neutrons became protons at equal rates; however, as the universe expanded and cooled, neutrons became protons at twice the rate that protons became neutrons.
All of the neutrons would have eventually been lost, but Big Bang Nucleosynthesis (BBN) began to force protons and neutrons together and form helium nuclei. The helium nuclei provided a stable environment for neutrons and preserved them. Two of the fundamental forces of nature, electromagnetic and strong nuclear, governed the formation of helium nuclei during nucleosynthesis. There was a limited window of opportunity for the formation of nuclei when there was enough energy in the young universe to overcome the force of electromagnetic repulsion that keeps protons apart. High energy and density forced nucleons into close enough proximity so that the strong nuclear force could bind them together. Even this would not have been possible were it not for the process of “tunneling through the wall” in which the uncertain positions of particles (wavefunction) due to quantum mechanics allowed them to cross an energy barrier that would otherwise be too high to overcome.
Figure 2-21. Hydrogen (hydronium) atom (H) and Helium atom (He) with protons (red circles), neutrons (green circles), filled electron positions (white circles), and unfilled electron positions (black circles).
The primary elements after Big Bang nucleosynthesis were hydrogen and helium (Figure 2-21). Hydrogen has only one proton, so it has only one electron. The inner electron shell (only electron shell in hydrogen and helium) has positions for two electrons (two orbitals), with the white dot representing an electron and the black dot representing an unfilled electron position in the shell. Helium has two protons, so the electron shell is filled with two electrons in the helium atom. Heavier elements than helium (and a small amount of boron that decayed) would not form until the first stars.
Banner
Banner
Quark gluon plasma during first millionth of a second in the universe. Credit S13machina. Used here per CC BY-SA 4.0
References
References
[1] Cline, James, M. “Is Electroweak Baryogenesis Dead?” Phil. Trans. R. Soc. A 376, no. 2114 (20 18): 20170116
Page updated
Report abuse