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A GUT model basically consists of a gauge group which is a compact Lie group, a connection form for that Lie group, a Yang-Mills action for that connection given by an invariant symmetric bilinear form over its Lie algebra ( which is specified by a coupling constant for each factor ), a Higgs sector consisting of a number of scalar fields taking on values within real / complex representations of the Lie group and chiral Weyl fermions taking on values within a complex rep of the Lie group.
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GUT and model
A Grand Unified Theory, ( GUT ), is a model in particle physics in which at high energy, the three gauge interactions of the Standard Model which define the electromagnetic, weak, and strong interactions, are merged into one single interaction characterized by one larger gauge symmetry and thus one unified coupling constant.
Due to this difficulty, and due to the lack of any observed effect of grand unification so far, there is no generally accepted GUT model.
Most GUT models also predict proton decay, although not the Pati-Salam model ; current experiments still haven't detected proton decay.
In particle physics, the Georgi – Glashow model is a particular grand unification theory ( GUT ) proposed by Howard Georgi and Sheldon Glashow in 1974.
In physics, the Pati – Salam model is a Grand Unification Theory ( GUT ) was proposed in 1974 by nobel laureate Abdus Salam and Jogesh Pati.
This model doesn't predict gauge mediated proton decay ( unless it is embedded within an even larger GUT group ).
The Flipped SU ( 5 ) model is a Grand Unified Theory ( GUT ) theory first contemplated by Stephen Barr in 1982, and by Dimitri Nanopoulos and others in 1984.
Flipped SU ( 5 ) is not a fully unified model, because the U ( 1 ) y factor of the SM gauge group is within the U ( 1 ) factor of the GUT group.
In physics, the trinification model is a GUT theory.
Cryptons arising in the hidden sector of a superstring-derived flipped SU ( 5 ) GUT model have been shown to be metastable with a lifetime exceeding the age of the universe.
If the hypercharge is contained within SU ( 5 ), this is the conventional Georgi-Glashow model, with the 16 as the matter fields, the 10 as the electroweak Higgs field and the 24 within the 45 as the GUT Higgs field.
When this Higgs field acquires a GUT scale VEV, we have a symmetry breaking to Z < sub > 2 </ sub > ⋊ × SU ( 2 )< sub > L </ sub > × SU ( 2 )< sub > R </ sub >/ Z < sub > 2 </ sub >, i. e. the Pati-Salam model with a Z < sub > 2 </ sub > left-right symmetry.
This is a standard practice in the GUT model building literature anyway ).
GUT and gauge
The renormalization group running of the three gauge couplings in the Standard Model has been found to nearly, but not quite, meet at the same point if the hypercharge is normalized so that it is consistent with SU ( 5 ) or SO ( 10 ) GUTs, which are precisely the GUT groups which lead to a simple fermion unification.
The gauge coupling strengths of QCD, the weak interaction and hypercharge seem to meet at a common length scale called the GUT scale and equal approximately to 10 < sup > 16 </ sup > GeV, which is slightly suggestive.
GUT and group
Historically, the first true GUT which was based on the simple Lie group SU ( 5 ), was proposed by Howard Georgi and Sheldon Glashow in 1974.
The GUT group E < sub > 6 </ sub > contains SO ( 10 ), but models based upon it are significantly more complicated.
The grand unification energy, or the GUT scale, is the energy level above which, it is believed, the electromagnetic force, weak force, and strong force become equal in strength and unify to one force governed by a simple Lie group.
In particle physics, one of the grand unified theories ( GUT ) is based on the SO ( 10 ) Lie group.
To see this, note that with a 16 < sub > 1H </ sub > and a Higgs field, we can have VEVs which breaks the GUT group down to × U ( 1 )< sub > χ </ sub >/ Z < sub > 4 </ sub >.
GUT and which
The new particles predicted by models of grand unification cannot be observed directly at particle colliders because their masses are expected to be of the order of the so-called GUT scale, which is predicted to be just a few orders of magnitude below the Planck scale and thus far beyond the reach of currently foreseen collision experiments.
, all GUT models which aim to be completely realistic are quite complicated, even compared to the Standard Model, because they need to introduce additional fields and interactions, or even additional dimensions of space.
He ignored magnetic monopoles because they were based on assumptions of GUT, which was outside the scope of the speech.
Some theorists found this objectionable, and so proposed a GUT extension of the weak force which has new, high energy W ' and Z ' bosons which couple with right handed quarks and leptons.
The masses of the doublets have to be stabilized at the electroweak scale, which is many orders of magnitude smaller than the GUT scale whereas the triplets have to be really heavy in order to prevent triplet-mediated proton decays.
GUT and is
SU ( 5 ) is the simplest GUT.
Since Majorana masses of the right-handed neutrino are forbidden by SO ( 10 ) symmetry, SO ( 10 ) GUTs predict the Majorana masses of right-handed neutrinos to be close to the GUT scale where the symmetry is spontaneously broken in those models.
Some GUT theories like SU ( 5 ) and SO ( 10 ) suffer from what is called the doublet-triplet problem.
These theories predict that for each electroweak Higgs doublet, there is a corresponding colored Higgs triplet field with a very small mass ( many orders of magnitude smaller than the GUT scale here ).
The discovery of neutrino oscillations indicates that the Standard Model is incomplete and has led to renewed interest toward certain GUT such as SO ( 10 ).
One of the few possible experimental tests of certain GUT is proton decay and also fermion masses.
In this graph, electroweak unification occurs at around 100 GeV, grand unification is predicted to occur at 10 < sup > 16 </ sup > GeV, and unification of the GUT force with gravity is expected at the Planck energy, roughly 10 < sup > 19 </ sup > GeV.
It may be that any others that may exist at the GUT or Planck scale simply become too weak to detect in the realm we can observe, with one exception: gravity, whose exceedingly weak interaction is magnified by the presence of the enormous masses of stars and planets.
Of course, calling the representations things like and ( 6, 1, 1 ) is purely a physicist's convention, not a mathematician's convention, where representations are either labelled by Young tableaux or Dynkin diagrams with numbers on their vertices, but still, it is standard among GUT theorists.
GUT and form
Supersymmetric GUTs seem plausible not only for their theoretical " beauty ", but because they naturally produce large quantities of dark matter, and because the inflationary force may be related to GUT physics ( although it does not seem to form an inevitable part of the theory ).
GUT and for
The acronym GUT was first coined in 1978 by CERN researchers John Ellis, Andrzej Buras, Mary K. Gaillard, and Dimitri Nanopoulos, however in the final version of their paper they opted for the less anatomical GUM ( Grand Unification Mass ).
Most GUT models also fail to explain the little hierarchy between the fermion masses for different generations.
There are a few more special tests for supersymmetric GUT.
The GUT explained all the fundamental forces known in science except for gravity.
The Yukawa coupling causes 5 and a SU ( 5 )- rep of fermions to pair up and acquire GUT scale masses for each generation.
GUT and by
Image: Proton_decay2. svg | Dimension 6 proton decay mediated by the X boson in SU ( 5 ) GUT
Image: proton decay3. svg | Dimension 6 proton decay mediated by the X boson in flipped SU ( 5 ) GUT
Image: proton decay4. svg | Dimension 6 proton decay mediated by the triplet Higgs and the anti-triplet Higgs in SU ( 5 ) GUT
Calling the representations foe example, and 24 < sub > 0 </ sub > is purely a physicist's convention, not a mathematician's convention, where representations are either labelled by Young tableaux or Dynkin diagrams with numbers on their vertices, and is a standard used by GUT
Dimension 6 proton decay mediated by the boson in flipped GUT
Note that calling the representations things like and ( 8, 1, 1 ) is purely a physicist's convention, not a mathematician's convention, where representations are either labelled by Young tableaux or Dynkin diagrams with numbers on their vertices, but still, it is standard among GUT theorists.
The primary problem with these color triplet Higgs, is that they can mediate proton decay in supersymmetric theories that are only suppressed by two powers of GUT scale ( i. e. they are dimension 5 supersymmetric operators ).
Dimension 6 proton decay mediated by the triplet Higgs and the anti-triplet Higgs in GUT
0.159 seconds.