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In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, [1] [2] is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe.
This imbalance has to be exceptionally small, on the order of 1 in every 1 630 000 000 (≈ 2 × 10 9) particles a small fraction of a second after the Big Bang. [4] After most of the matter and antimatter was annihilated, what remained was all the baryonic matter in the current universe, along with a much greater number of bosons.
All the particles that make up the matter around us, such electrons and protons, have antimatter versions which are nearly identical, but with mirrored properties such as the opposite electric charge.
The local geometry of the universe is determined by whether the relative density Ω is less than, equal to or greater than 1. From top to bottom: a spherical universe with greater than critical density (Ω>1, k>0); a hyperbolic, underdense universe (Ω<1, k<0); and a flat universe with exactly the critical density (Ω=1, k=0). The spacetime of ...
Under current theory, the Big Bang explosion that initiated the universe should have produced equal amounts of matter and antimatter. This, however, does not seem to be the case.
This maximal radiation density corresponds to about 1.2 × 10 17 eV/m 3 = 2.1 × 10 −19 kg/m 3, which is much greater than the observed value of 4.7 × 10 −31 kg/m 3. [4] So the sky is about five hundred billion times darker than it would be if the universe was neither expanding nor too young to have reached equilibrium yet.
Many physicists also believe that inflation explains why the universe appears to be the same in all directions , why the cosmic microwave background radiation is distributed evenly, why the universe is flat, and why no magnetic monopoles have been observed. The detailed particle physics mechanism responsible for inflation is unknown.
[1] The lepton and baryon asymmetries affect the much better understood Big Bang nucleosynthesis at later times, during which light atomic nuclei began to form. Successful synthesis of the light elements requires that there be an imbalance in the number of baryons and antibaryons to one part in a billion when the universe is a few minutes old. [2]