When we look at the Universe, all its planets and stars, galaxies and clusters, gas, dust, plasma, we see everywhere the same signature. We see a line of atomic absorption and emission, we see that matter interacts with other forms of matter, we see star formation and death of stars, collisions, x-rays, and more. There is an obvious question that requires an explanation: why are we seeing all this? If the laws of physics dictate symmetry between matter and antimatter, the universe we observe should not exist.
But we’re here and nobody knows why.
Why in the Universe there is no antimatter?
Consider the two contradictory at first glance, the facts:
- Every interaction between particles, which we have ever observed at any energy, never created and did not destroy one particle of matter, without creating it or destroying an equal number of particles of animalerie. Physical symmetry between matter and antimatter is very strict, because:
- every time we create a quark or a lepton, we also create antiquark and antilepton;
- each time a quark or lepton is destroyed, antiquark or antilepton also destroyed;
- created or destroyed leptons and antileptons must be in balance for the whole family Leonov and every time the quarks and leptons interact, collide, or break apart, the total number of quarks and leptons at the end of the reaction (minus antiquark quarks, leptons minus antileptons) should be the same as it was in the beginning.
The only way to change the amount of matter in the Universe also implies a change in the amount of antimatter in the same amount.
And yet, there is a second fact.
- When we look at the Universe, all the stars, galaxies, gas clouds, clusters, superclusters and large scale structure, it seems like everything is made of matter and not antimatter. Everywhere, where antimatter and matter meet in the Universe, is a fantastic release of energy due to particle annihilation.
But we do not see any signs of destruction of matter and antimatter in the large scale. We see no signs that some of the stars, galaxies or planets which we see is made of antimatter. We do not see the characteristic gamma-rays which one would expect to see if antimatter faced with matter and annihilate. Instead, everywhere we see only matter everywhere you look.
And it seems impossible. On the one hand, there’s no known way to make more matter than antimatter, if we turn to particles and their interactions in the Universe. On the other hand, all that we see, definitely consists of matter and not antimatter.
In fact, we observed the annihilation of matter and antimatter in some extreme astrophysical conditions, but only near giperarifmeticheskie sources that produce matter and antimatter in equal amounts — black holes, for example. When antimatter collides with matter in the Universe, it produces gamma rays of very specific frequencies, which can then be detected. Interstellar intergalactic environment is full of material, and the complete absence of these gamma rays is a strong signal that no longer has a large number of antimatter particles, because then the signature of matter-antimatter would have been detected.
If you leave one speck of antimatter in our galaxy, it will last about 300 years before being destroyed by a particle of matter. This restriction tells us that in the milky Way the amount of dark energy cannot exceed a value of 1 for particles in a quadrillion (1015), relative to the total amount of matter.
For large scale — scale of satellite galaxies, large galaxies the size of milky Way and even clusters of galaxies — constraints are less stringent but still very strong. Watching the distance of several million light years to three billion light-years, we observed lack of x-rays and gamma rays, which could indicate the annihilation of matter and antimatter. Even in large cosmological scales of 99.999% of what exists in our Universe, would be represented by matter (like us), and not antimatter.
How did we get in such a situation that the universe consists of a large number of matter and practically no antimatter, if the laws of nature are perfectly symmetrical between matter and antimatter? Well, you have two options: either the universe was born with a large amount of matter than antimatter, or something happened early on, when the universe was very hot and dense, and created the asymmetry of matter and antimatter, which initially was not.
The first idea to test scientifically without recreating the entire Universe will not work, but the second is very convincing. If our universe is somehow created the asymmetry of matter and antimatter, where originally it was not, then the rules that worked then remain unchanged today. If we’re smart, we will be able to develop experimental tests that reveal the origin of matter in our Universe.
In the late 1960-ies physicist Andrei Sakharov outlined three conditions necessary for baryogenesis or create more baryons (protons and neutrons) than antibaryons. Here they are:
- The universe must be non-equilibrium system.
- It should be C – and CP-violation.
- Must be interactions that violate baryon number.
The first to observe simply because of the expanding and cooling universe with unstable particles (and antiparticles) are, by definition, will be out of balance. Second one is also simple as C-symmetry (the replacement of particles by antiparticles) and CP-symmetry (replacing the mirrored particles antiparticles) are violated in many weak interactions involving strange, charmed and beautiful quarks.
The question remains as to violate baryon number. Experimentally, we observed that the balance of antiquarks to quarks and leptons to antileptons clearly remains. But in the Standard model of particle physics there is no explicit conservation law for any of these quantities individually.
You need three quarks to make a baryon, so for every three quark, we assign the baryon number (B) 1. Similarly, every receive lepton lepton number (L) 1. Antiquark, antibaryon and antilepton will have negative numbers B and L.
But according to the rules of the Standard model is stored only the difference between baryons and leptons. Under the right circumstances, you can not only create additional protons, but also electrons to them. The exact circumstances are unknown, but the Big Bang has given them the opportunity to be realized.
The earliest stages of the Universe are described extremely high energy: high enough to create every known particle and antiparticle in a large number on the famous Einstein formula E = mc2. If the creation and destruction of particles works the way we think the early universe must be filled with an equal amount of particles of matter and antimatter, which mutually become each other because of the energy remained extremely high.
With the expansion and cooling of the Universe unstable particles, once created, in abundance, will be destroyed. Under the proper conditions — in particular, the three Sakharov conditions — this can lead to an excess of matter over antimatter, even if initially it was not. The challenge for physicists is to create a viable scenario corresponding to observations and experiments, which can give you a sufficient excess of matter over antimatter.
There are three main possibilities of occurrence of the excess of matter over antimatter:
- New physics at the electroweak scale can significantly increase the number of C – and CP-violation in the Universe, which will lead to asymmetry between matter and antimatter. Interactions of the Standard model (through the process of sphaleron), which violate B and L individually (but keep B — L) may set the amounts of baryons and leptons.
- New neutrino physics at high energies, which suggests the universe could create a fundamental asymmetry of leptons: leptogenys. Sphaleron that preserve B — L, and then could use the lepton asymmetry to create a baryon asymmetry.
- Or borigines the scale of Grand unification, if the new physics (and new particles) exist in the scale of Grand unification, when the electroweak force merges with the strong.
These scenarios have common elements, so let’s look at the last one, just for example, to understand what could happen.
If the Grand unified theory is correct, must be new, superheavy particles, called X and Y, which have as brianpdoyle and leptonetidae properties. Must also be partners of antimatter: anti-X and anti-Y, with the opposite numbers B — L and opposite charges but the same mass and life time. These pairs of particle-antiparticle can be created in large quantities at rather high energies, in order to subsequently disintegrate.
So, we fill the Universe with them, and then they disintegrate. If we have C – and CP-violation might be minor differences in how the decay of particles and antiparticles (X, Y and anti-X, anti-Y).
If X-particles there are two ways: the decay into two top quarks and two anti-bottom quark and a positron, then anti-X must pass two related ways: two anti-top quark or bottom quark and the electron. There is an important difference that is allowed for violation of C and CP: X may be more likely to decay into two top quarks than anti-X — two anti-top quark, whereas the anti-X are more likely to decay into bottom quark and the electron, than X — anti-top quark and a positron.
If you have a sufficient number of pairs and decay so you can easily get an excess of baryons over antibaryons (and leptons over antileptons), where it did not exist.
This is just one example illustrating our view of what happened. We started with a completely symmetrical Universe, obeying all known laws of physics, and with a hot, dense, rich state, filled with matter and antimatter in equal amounts. Using the mechanism that we have yet to determine, subject to the three conditions of Sakharov, these natural processes are ultimately created a surplus of matter over antimatter.
The fact that we exist is made of matter, is undeniable; the question is, why our universe contains something (matter) and nothing (because of matter and antimatter were equally). Perhaps in this century we find the answer to this question.
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