Questions tagged [grand-unification]

A Grand Unified Theory is a model in particle physics in which at ultra-high energy, the 3 gauge interactions of the Standard Model (electromagnetic, weak, and strong) merge into a single one, characterized by one larger encompassing gauge symmetry and one unified coupling constant. After SSBreaking, force carriers differentiate themselves and are driven by the RG to their values and numbers in the lab. Use for gauge GUT and gravity unification.

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What does this curly bracket notation mean?

I came across this $$\langle H_A^{i\{1,\,k\}}\rangle=f^{i\{1,\,k\}},\,\langle H_{A\{1,\,k\}i}\rangle=f_{A\{1,\,k\}i},\,i,\,k=2,\,3$$ curly bracket notation to denote VEVs (vacuum expectation values) ...
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Standard model embedding in GUT

Supposing we have a general representation in SU(5) for example 75 which is a rank 4 tensor (2,2), so call him $T_{ij}^{lm}$, now we know that SM is embedded in SU(5), so supposing that \begin{...
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GUT decomposition

How can we decompose a generic $SU(5)$ irreducible representation as a direct sum of irreducible $SU(3) \times SU(2) \times U(1)$ representations?
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In an $SO(10)$ GUT, how many gauge fields acquire masses that are above the electro-weak scale?

The $SO(10)$ group is spontaneously broken down into the Standard Model gauge group at around $10^{16}$ GeV and the electroweak scale is ~246 GeV. I think there should be 45 gauge fields predicted by ...
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Why must $U(1)$ matrices commute with $SU(2) \times SU(3)$ matrices in embedding within $SU(5)$?

I'm a physicist taking a groups course. I can believe that the direct sum of the fundmental representations for the $SU(2)$ and $SU(3)$ matrices will work as an embedding of the $SU(2) \times SU(3)$ ...
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Have magnetic monopoles been predicted to have been produced in other cases than those of symmetry breaking in GUTs?

Also, what other configurations are magnetic monopoles theorized to exist in? (such as black holes, monopole walls etc.)
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Deduction of weak boson hypercharge in Georgi–Glashow $SU(5)$ grand unified theory (GUT)

In the Georgi–Glashow model, the extra 12 bosons $X_\mu^a$, $Y_\mu^a$ that appear have weak hypercharge $y = -\frac{5}{6}$. I want to know how this is deduced from the weak hypercharge generator $$Y = ...
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A question on the electrostrong force

I understand that the strong nuclear force is carried by gluons, the electromagnetic force is carried by photons and the weak nuclear force is carried by the $W$ and $Z$ bosons. However, in the ...
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By which interaction will proton decay? [duplicate]

I learned that proton takes at least $10^{34}$ years to decay. If it will decay one day, will it decay via weak interaction or some other interaction?
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Gauge boson layout in $\rm SU(5)$ GUT unification

It is known that the theory of the Great Unification $\rm SU(5)$ GUT encapsulates the gauge groups of the standard model to one large group $\rm SU(5)$. But is it possible to show schematically how to ...
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Would there be a force carrier particle in the unified field theory?

So from what I understand, each fundamental force (with the exception of gravity unless you count the hypothetical graviton) has a force carrier particle that mediates the force. Does that mean if the ...
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Tensor product of fundamental representation of $SU(5)$

In Srednicki's QFT book (see pg. 605) he writes that the fundamental representation of $SU(5)$ may be written as (97.2), $$ 5\to \left(3,1,-\frac{1}{3}\right)\otimes \left(1,2, +\frac{1}{2}\right).\...
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What particles are thought to have existed before Inflation?

What fundamental particles do most Grand Unified and Inflationary theories predict existed before the Inflationary period? Basically, what do we expect the family of particles existing during the ...
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Name for 16⊕1͞6 bosons of E6 & larger GUTs?

E6 GUTs put fermions into $27→16_1⊕10_{-2}⊕1_4$ and gauge bosons into $78→45_0⊕16_{-3}⊕\overline{16}_{3}⊕1_0$. And larger GUTs (e.g. E8 on 𝕋⁶/ℤ₆×ℤ₂, E8 on 𝕋⁶/ℤ₃×ℤ₃) usually incorporate these. The $...
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Are orbifolded 10d E8 GUTs valid low-energy EQFTs of string theory? Or swampland?

AdAMP recently proposed a string-reminiscent E8 GUT (digest, full) where 6 extra dimensions are compactified on a $\mathbb T^6/(\mathbb Z_3\times\mathbb Z_3)$ orbifold to yield the 4d Standard Model. ...
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10-dimensional and 15-dimensional matrix representations of $SU(5)$: explicit 24 Lie algebra generators

There are some previous discussions in this post Representation of the $\rm SU(5)$ model in GUT which confused me. So I want to follow up with a new question. It is easy to write down the 5-...
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What's the mathematical explanation of the emergence of magnetic monopoles during the early universe?

I would "simply" like to know the full mathematical explanation of: Why do these topological defects occur in the first place? And more importantly, Why must these defects/particles carry ...
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What is the status of orbifolded 10D E8 theory?

A recent series of papers (1, 2) presents an $E_8$ GUT in 10 dimensions, where compactification on a $\mathbb T^6/(\mathbb Z_3\times\mathbb Z_3)$ orbifold ($\mathbb T^6/(\mathbb Z_6\times\mathbb Z_2)$ ...
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Zee Chapter VII.5: Can the fermion $10$ be the composite of fermion $5^*$?

In Zee Chapter VII.5 QFT book: He showed that the standard model fermions form $5^*$ and $10$ representations of $SU(5)$: $$ 5^* \oplus 10. $$ In particular, the $10$ is the anti-symmetric matrix ...
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Georgi: existence of right-handed neutrinos cause problems in particle physics and cosmology

In Georgi book Lie Algebras in Particle Physics 2ed - From Isospin to Unified Theories (1999) in p.285: "existence of right-handed neutrinos -- It has not been seen, and if it were present, it ...
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Figure of $SO(10)$ grand unified theory in $E_6$ from Wikipedia

In this figure from Wikipedia, it shows that the representations of particles of $SO(10)$ grand unified theory, their patterns of charges for particles in the $SO(10)$ model, rotated to show the ...
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Figure of $SO(10)$ grand unified theory from Wikipedia

In this Figure from Wikipedia, it shows that the representations of particles of $SO(10)$ grand unified theory, representations as numbers labeled in several axes. Descriptions: The patterns of weak ...
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CERN LHCb leptoquarks and grand unified theory

Recent CERN LHCb experiment suggests possible leptoquarks as new particles beyond the standard model may be discovered, with 3.1 $\sigma$ not the 5 $\sigma$ discovery. What are the viable candidates ...
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Would the recently suspected violation of Lepton universality in $B$ meson decays implicate that the Grand unification occurs at a lower energy scale?

Articles like https://physicsworld.com/a/has-a-new-particle-called-a-leptoquark-been-spotted-at-cern/ report on a difference in the $B$ meson decay chain in electrons to muons which amounts to now $3....
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How Can I Find Good Resources to Learn About the $SU(5)$ and $SO(10)$ Grand Unified Theories Without an Extensive Background in the Field?

I'm a first-year university student. My group and I have been tasked with finding out whether, given current scientific consensus, it looks like a viable Grand Unified Theory (GUT) can be found. We ...
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Does a grand unified field theory need to include a Dark Energy field? [closed]

Nobody has unified field theories yet but could dark energy if considered as a field be useful in this endeavour?
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Error in Wikipedia on a flipped $SO(10)$ model

In the description of Wikipedia of flipped SO(10) model, it says that: In flipped $SO(10)$ models, however, the gauge group is $[SO(10)_F × U(1)_B]/Z_4$. If we suppose $[SU (5) × U(1)_χ ]/ Z_5$ ...
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Disadvantages of flipped $SU(5)$ model

Question: What are the advantages and disadvantages of flipped $SU(5)$ model? We know the fermions (same form for three families), each consisting of the representations $\overline{5}_{−3}$ for the ...
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Does the lack of evidence for proton decay really rule out the basic grand unification theories?

Grand unification theories (GUT), such as $SU(5)$/$SO(10)$/SUSY variants, suggest proton decay. The lack of observational evidence for proton decay is supposed to rule out basic GUTs, at least for the ...
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$\text{SU}(5)$ GUT Higgs sector and symmetry breaking

The Higgs sector of minimal $\text{SU}(5)$ GUT consists of scalar fields in two representations, a $\mathbf{24}$ and a $\mathbf{5}$. All the $\mathbf{5}$ non-derivative terms form the potential $V(\...
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Proton decays in Pati Salam model or Georgi Glashow model

This Pati-Salam model doesn't predict gauge mediated proton decay, according to Wikipedia. However the Georgi-Glashow model predict gauge mediated proton decay, according to Wikipedia. I thought the ...
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Has the number of particle types changed in the GUT era and after?

The Wikipedia article on Grand Unified Theory says: "GUT models predict that at even higher energy, the strong interaction and the electroweak interaction will unify into a single electronuclear ...
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There was no electromagnetic field at the moment of the Big Bang. Did it appear later?

After the big bang, the fundamental interactions were one, but over time they began to separate. This is evidenced by the Grand Unification model. Do I understand correctly that at the time of the big ...
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Zee QFT book on the neutrino mass

in p.102 of Zee QFT book, "As of this writing, it is not known whether the neutrino mass is Dirac or Majorana. We will see in chapter VII.7 that a Majorana mass for the neutrino arises naturally ...
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Adjusting the rate of proton decay in the standard $\rm SU(5)$ grand unified theory

The proton decay rate in the standard $SU(5)$ grand unified theory is given by $$ \Gamma \sim \left(\frac{g^2}{M_x^2}\right)^2 m_p^5 =\frac{g^4}{M_x^4}m_p^5 $$ Naively we could push up the bound for ...
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Magnetic Monopoles and the Inflationary Epoch

What leads to magnetic monopoles existing before the Inflationary Epoch and becoming infinitely diluted during inflation (if indeed that is the explanation to their absence), but the electric ...
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What is string theory? Why was a new theory required when modern Physics was only one step away from establishing a G.U.T.? [closed]

What is string theory ? (correct me if i am wrong) Why a new underlying theory was required when modern Physics was only one step away from establishing a G.U.T. (unification attempt for four ...
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Why don't $\rm SO(10)/Spin(10)$ or larger GUTs permit electron-pair decay?

$\rm Spin(10)$ unifies all left-handed fermions and anti-fermions, and all right-handed fermions and anti-fermions. And its Pati-Salam subgroup unifies quarks with leptons (SU(4)) and complements SU(...
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$ (5^* \times 5^*)_{asym}={10}$ in A. Zee's book p.409 versus PDG Sec.114

What is the mathematical or physical way to understand why the 4th and 5th components in the Georgi Galshow SU(5) model has the SU(2) doublet $(1,2,-1/2)$: $$ \begin{pmatrix} \nu\\e \end{pmatrix} $$ ...
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Georgi statements about the symmetry breaking of $\rm SO(10)$

Here is a paragraph with some statements about the Gauge Symmetry Breaking from Georgi's book Lie Algebras in Particle Physics 2nd ed -- From Isospin to Unified Theories (Georgi, 1999) p.285. Georgi ...
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$\rm SO(10)$ grand unified model restores the parity symmetry lost in $\rm SU(5)$ model

It is said in Lie Algebras in Particle Physics 2ed - From Isospin to Unified Theories (Georgi, 1999) p.285, Georgi said that $\rm SO(10)$ grand unified model restores the parity symmetry that was ...
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How to give left-handed neutrinos alone Majorana mass?

The Wikipedia page on Georgi–Glashow model says Fermions transforming as a 1 under SU(5) are now thought to be necessary because of the evidence for neutrino oscillations, unless a way is found to ...
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Light composite fermion as a bound state formed by $SU(4)$ gauge force attractions

In this paper https://inspirehep.net/literature/152400, in eq.(3.4), it claims that the MAC (most attractive channel) in $SU(4)$ gauge theory will attract fermions in $[1]_4$ and fermions in $[3]_4$ ...
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Quark mass vs Lepton mass $m_d/m_e$

In Zee QFT in a nutshell book p.418, Zee said about Quark mass vs Lepton mass $m_d/m_e$ : He first mentioned $m_d/m_e=1$ for unification scale. Then he mentioned $m_d/m_e\sim 3 $ in eq.15. Are ...
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Electroweak Unification and Electroweak scale

We said that the EM and weak interactions are unified as Electroweak Unification. However, for usual Grand Unification, it requires that the gauge group G is simple Lie group -- which means the G has ...
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Monopole problem: 't Hooft–Polyakov, Big Bang theory versus Cosmic inflation

I am not sure the validity of this claim from Wikipedia on 't Hooft–Polyakov_monopole The "monopole problem" refers to the cosmological implications of grand unification theories (GUT). ...
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$SU(5)$ model and flipped $SU(5)$ model

It seems that both $SU(5)$ model and flipped $SU(5)$ model are legal grand unified theories (GUT) for the standard model gauge group. In Wikipedia, it says that: The flipped $SU(5)$ model has a gauge ...
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Lectures by Susskind versus Zee on the ${\rm SU}(5)$ grand unified theory notations

I was comparing two lectures about ${\rm SU}(5)$ grand unified theory. a lecture of Susskind He showed how to write $$ (5 \times 5)_{asym}=\bar{10} $$ as a lecture of Zee showed how to write $$ (\...
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Are X and Y boson gauge mediator of X and Y gauge symmetry? With zero X and Y charge?

Recall that the electron carries U(1) gauge charge -1. the U(1) is gauged and mediated by the U(1) gauge boson which is the photon with zero U(1) gauge charge, thus $0$. Now let us take this ...
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Bern-Carrasco-Johansson (BCJ) Double Copy and Color-Kinematic duality

According to the wikipedia page on Strong Gravity, the theory is considered "non-mainstream", but from what I can gather there have been some very interesting progress and results since it ...
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