Theories of the great unification (GUT, GUT or TVO - all three abbreviations will be used in the article) is a model in particle physics, in which at high energy the three gauge interactions of the standard model, which determine electromagnetic, weak and strong interactions or forces, are combined into one single power. This combined interaction is characterized by one symmetry of greater calibration and, therefore, several bearing forces, but one constant bond. If a great unification is realized in nature, there is a possibility of an era of great unification in the early Universe, in which the fundamental forces are not yet different.
Grand Unification Theory: Briefly
Models that do not combine all interactions using one simple group as gauge symmetry, do this using semisimple groups, can exhibit similar properties and are sometimes also called great union theories.
Combining gravity with three other interactions would provide the theory of everything (OO), not GUT. However, GUTs are often seen as an intermediate step to the TOE. All these are characteristic ideas for the great theories of unification and superunification.
The new particles predicted by the GUT models are expected to have masses around the GUT scale - just a few orders of magnitude lower than the Planck scale - and therefore will not be available for any proposed particle collider experiments. Consequently, particles predicted using the GUT models cannot be directly observed, and instead the effects of grand unification can be detected by indirect observations, such as proton decay, electrical dipole moments of elementary particles, or neutrino properties. Some GUTs, such as the Pati-Salam model, predict the existence of magnetic monopoles.
Feature Models
GUT models that strive to be completely realistic are quite complex, even compared to the standard model, because they must introduce additional fields and interactions, or even additional dimensions of space. The main reason for this complexity is the difficulty in reproducing the observed fermion masses and mixing angles, which may be due to the existence of some additional family symmetries outside the traditional GUT models. Due to this difficulty and the absence of any observable effect of great unification, there is still no generally accepted GUT model.
Historically, the first true GUT based on Lee’s simple SU group was proposed by Howard George and Sheldon Glashow in 1974. The Georgi-Glashow model was preceded by the semisimple Lie algebra of the Pati-Salam model proposed by Abdus Salam and Jogesh Pati, who first proposed combining gauge interactions.
Name history
The abbreviation GUT (TVO) was first coined in 1978 by CERN researchers John Ellis, Andrzej Buras, Mary K. Gaillard and Dmitry Nanopoulos, but in the final version of their article, they chose GUM (the mass of the great association). Nanopoulos later that year was the first to use the abbreviation in the article. In short, a lot of work has been done on the way to the theory of great unification.
Common concepts
The abbreviation SU is used to refer to theories of grand unification, which will often be mentioned in this article. The fact that the electric charges of electrons and protons, apparently, mutually cancel each other with extreme accuracy, is essential for the macroscopic world, as we know it, but this important property of elementary particles is not explained in the standard model of elementary particle physics. While the description of strong and weak interactions in the standard model is based on gauge symmetries controlled by simple symmetry groups SU (3) and SU (2), which allow only discrete charges, the remaining component, the interaction of a weak hypercharge, is described by the abelian symmetry U (1 ), which in principle allows an arbitrary distribution of charges.
The observed quantization of the charge, namely the fact that all known elementary particles carry electric charges, which appear to be exact multiples of the elementary charge, has led to the idea that hypercharged interactions and, possibly, strong and weak interactions can be embedded in one great combined interaction, described by one larger simple symmetry group containing a standard model. This will automatically predict the quantized nature and values of all charges of elementary particles. Since this also leads to a prediction of the relative strengths of the main interactions that we observe, in particular, to a weak mixing angle, Grand Unification ideally reduces the number of independent input parameters, but is also limited to observations. No matter how universal the theory of the great unification might seem, books on it are not very popular.
Georgie-Glasgow Theory (SU (5))
The great unification resembles the unification of electric and magnetic forces according to Maxwell’s theory of electromagnetism in the 19th century, but its physical significance and mathematical structure are qualitatively different.
However, it is not obvious that the simplest possible choice for extended grand combined symmetry should give the correct set of elementary particles. The fact that all currently known particles of matter fit well into the three smallest theories of group representations SU (5) and immediately carry the correct observed charges is one of the first and most important reasons why people believe that the great theory of unification can actually be realized in nature.
The two smallest irreducible representations of SU (5) are 5 and 10. In the standard assignment, 5 contains charge conjugates of the color triplet of the right-handed descending type quark and the isospin doublet of the left-handed levton, while 10 contains six components of the ascending type quark, the color triplet of the left descending type quark and right-handed electron. This pattern must be reproduced for each of the three known generations of matter. It is noteworthy that the theory does not contain anomalies with this content.
Hypothetical right-handed neutrinos are the SU (5) singlet, which means that its mass is not forbidden by any symmetry; it does not need spontaneous symmetry breaking, which explains why its mass will be large.
Here, the union of matter is even more complete, since the irreducible spinor representation 16 contains both 5 and 10 of SU (5) and a right-handed neutrino, and thus the total content of particles of one generation of the extended standard model with neutrino masses. This is already the largest simple group that achieves the unification of matter in a scheme that includes only already known particles of matter (except for the Higgs sector).
Since various standard model fermions are grouped into larger representations, the GUT specifically predicts the relationships between the masses of fermions, such as between an electron and a lower quark, a muon and a strange quark, as well as a tau lepton and lower quark for SU (5). Some of these mass ratios are performed approximately, but most do not.
SO Theory (10)
The bosonic matrix for SO (10) is found by taking the 15 × 15 matrix from the 10 + 5 representation of SU (5) and adding an additional row and column for the right neutrino. The bosons can be found by adding a partner to each of the 20 charged bosons (2 right W-bosons, 6 massive charged gluons and 12 X / Y bosons) and adding an extra heavy neutral Z-boson to make 5 neutral bosons. The bosonic matrix will have a boson or its new partner in each row and column. These pairs combine to create the familiar 16D Dirac spinor matrices SO (10).
Standard model
The non-chiral extensions of the standard model with vector spectra of split multiplet particles that naturally appear in higher SU (N) GUTs significantly change desert physics and lead to a realistic (row-wide) grand union for the usual three quark-lepton families even without supersymmetry ( see below). On the other hand, due to the emergence of a new missing VEV mechanism arising in the supersymmetric SU (8) GUT, a simultaneous solution to the problem of gauge hierarchy (doublet-triplet splitting) and the problem of combining aroma can be found.
Other theories and elementary particles
GUT with four families / generations, SU (8): assuming that 4 generations of fermions instead of 3 form a total of 64 types of particles. They can be placed in 64 = 8 + 56 representations of SU (8). This can be divided into SU (5) × SU (3) F × U (1), which is the theory of SU (5), along with some heavy bosons that affect the generation number.
GUT with four families / generations, O (16): again, assuming 4 generations of fermions, 128 particles and antiparticles can be placed in one spinor representation of O (16). All these things were open to the theory of great unification.