The baryon asymmetry problem

In the scientific field of cosmology, the baryon asymmetry problem – which is also named; matter-antimatter asymmetry problem, and the matter asymmetry problem, can be described as an imbalance in baryonic matter (general matter of life or atoms) and, antibaryonic matter within the universe.

Logically after the Big Bang, the universe should of been abundant in both matter and antimatter, in equal amounts. But, as it stands, the universe has an abundance of matter, as opposed to antimatter. In essence, the universe is created mostly from matter, from the smallest lifeforms on Earth to the largest objects found floating in deep space. It is a notable challenge for scientists to figure out why the universe is more abundant in matter than antimatter.

To explain the unequal equilibrium of matter and antimatter, this article will examine; baryon number violation, CP violation (violation of CP-symmetry), and non-equilibrium of the universe after the Big Bang. As the free quarks cannot be observed, and the baryons are created via quarks and gluons, it is important to assess how the baryons were first formed via the non-equilibrium quarks and gluons. This will allow the understanding of the baryon asymmetry of the universe.

Quark-Gluon Plazma

The quark-gluon plasma was formed ∼ 10−12 − 10−4 seconds following the Big Bang, quark-gluon plasma is comprised of quarks and gluons. Interaction between quarks and gluons is made possible by a strong force named both; nuclear force, and QCD force.

Hadronization (formation of hadrons out of quarks and gluons) of the quark-gluon plasma happened around 10-4 seconds after the Big Bang. At this time the temperature of the universe was < 200 MeV (200 million electronvolts) ( < 1012K).

What is an electronvolt?

An electronvolt can be described in physics as an amount of kinetic energy. The kinetic energy can be either gained or lost by a single electron accelerating from a static point, through an electric potential difference. An electric potential difference can be described as; the difference in electric potential between two points, and is denoted symbolically by $∆ V, for example; in the context of Ohm’s or Kirchhoff’s circuit laws.$

Quark-Gluon Plazma – continued

Protons and neutrons as a whole are called nucleons, they were first formed via quark-gluon plasma. The protons and neutrons are named baryons, while the antiprotons and antineutrons are named antibaryons.

Via, astrophysical experiments it has become apparent that there is more matter (baryons) than antimatter (antibaryons). The experimental evidence that proposes this, has been named the matter-antimatter asymmetry, or baryon asymmetry of the universe.

To explain the matter-antimatter, or baryon asymmetry of the universe, we need to address three conditions, that were suggested to be present; baryon (matter) number violation at the GUT (grand unified theory) energy scale, CP (charge conjugation parity symmetry) violation at the electroweak energy scale and, nonequilibrium universe evolution, shortly following the big bang.

Baryons and antibaryons are quite different to quarks and gluons, this is because quarks and gluons carry color charges, while baryons and antibaryons do not possess color charges, meaning they are colorless. Since we have not physically observed quarks and gluons, but we have observed hadrons (a hadron is a subatomic composite particle which consists of two or more quarks held together by the strong force – summed up as mostly protons and neutrons – which form baryons and antibaryons). Quarks and gluons are restricted within the hadron (example: within a baryon or antibaryon) because of the restriction in QCD (quantum chromodynamics), not applicable to QED (quantum electrodynamics). Thus, why it is fundamental to understand why, and how baryons / antibaryons were created via non-equilibrium quarks and gluons – ∼ 10−4 seconds after the Big Bang, to understand the baryon asymmetry of our universe.

Formation of quarks and gluons can be studied by using non-perturbative QCD (quantum chromodynamics). None-equilibrium quarks, and gluons that form baryons and antibaryons can be scientifically studied via nonequilibrium-nonperturbative QCD (quantum chromodynamics). Nonequilibrium QCD (quantum chromodynamics) is typically studied from first principle (a basic proposition or assumption that cannot be deduced from any other proposition or assumption) by utilizing closed-time path (used to express) quantum field theory. Thus the importance to understand nonequilibrium-nonperturbative QCD from the first principle.

Theories to follow 🙂