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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Generators of the (1,2,2) of Pati-Salam

I am working on a project involving breaking SO(10) to its Pati-Salam sub group. In one of the path ways you can use, the broken generators fit in the (6,2,2) of Pati-Salam (recall the Pati-Salam ...
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How to prove $Q_u = -2Q_d$ from $SU(5)$?

I'm a beginner, and I'm trying to figure out how to prove that charge of Up quark is equal to 2 times the charge of down quark from the 10 representation of $SU(5)$. Please help.
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Unification of forces in black hole singularity?

If at the center of a black hole a singularity or singularity-like state is reached, wouldn't you have the fundamental forces reaching unification energy? In which case, it would seem that a black ...
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152 views

$B$-$L$ global symmetry in the grand unification theories

What are the precise $B$-$L$ (baryon - lepton) global symmetry in the standard model? Is this a $U(1)$ global symmetry or a discrete finite group $\mathbb{Z}/N$ global symmetry for the following ...
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64 views

Can a GUT be spontaneously broken mutiple ways?

Say we have a GUT e.g. $SU(5)$, if the Higgs field breaks this it can break it down to $SU(3)\times SU(2)\times U(1)$ if the Higgs field acquires values proportional to the weak hypercharge. But can ...
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Is there a symmetry breaking model possible for mirror fermions in $E_8$?

I've often been struck by how nicely the Standard model seems to fit into (supersymmetric) $E_8$. Specifically if we write the root vectors of $E_8$ as $(R,G,B,W,H,F,S,T)$. With colour being the ...
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Are there fermionic bound states that are gauge neutral to all gauge forces?

Puzzle: In our standard model particle physics, are there fermionic bound states that are gauge neutral to all gauge forces? Here we concern strong SU(3) color, electromagnetic U(1) EM, hyper U(1), ...
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Why are magnetic monopoles hard to find (if exist)?

I understand the Yang-Mill perspective of $U(1)$-gauge theory. In that, you can easily write down the field of a Dirac magnetic monopole. What interests me is the fact that it's so hard to find (if ...
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$\Delta {b_{L}}$, $\Delta {b_{Y}}$ and $\Delta {b_{C}}$ and unification of couplings

In any standard book on QFT, I understand how to find out the beta function for Standard Model and for Minimal Supersymmetric Standard Model, but i could not understand how this beta function changes ...
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Why does inflationary expansion of the very early universe require time duration?

If the grand unified force symmetry breaking separation into the strong force and electroweak force leads to a change in scale of the metric that defines distance within space is the cause of the ...
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In which representation are monopoles of grand unifying theories classified?

In the context of grand unification theories A.Zee's book states that $SU(5)$ (or $SO(10)$ if $SU(5)$ is considered as outdated as GUT candidate) as GUT and as spontaneously broken non-abelian gauge ...
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Representation of the $\rm SU(5)$ model in GUT

In Srednicki's textbook Quantum Field Theory, section 97 discusses Grand Unification. On page 606, it states: In terms of $\rm SU(5)$, we have \begin{equation} 5 \otimes 5 = 15_{S} \oplus 10_{A} ...
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How the hierarchy of forces is explained by Supersymmetry?

The hierarchy problem is often stated in two ways: First, the divergent corrections to the Higgs bare mass, second, why is gravity so much weaker than the other three forces. The solution to the ...
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What processes conserve (and don't conserve) GUT $X$-charge?

I've been Wikipedia-ing the weak interaction and GUTs and I came across 2 seemingly conflicting pieces of information. In the page for Weak Hypercharge it says this: one of the interactions is with ...
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What is the way to work out the running of lepton masses?

If we assume the GUT unification energy is some value E, (say $10^{16}GeV$). Can we work out the running of the particle masses for example the electon, muon and tau at various energies? And will ...
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Interaction range of fundamental forces at a unification energies

At low energies, all fundamental forces have different coupling constants as well as an interaction ranges. As one know, at a some high energy (GUT energy $10^{14}$ GeV), all the coupling constants ...
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Mass splitting for leptons and down quarks in $SU(5)$ model?

In the minimal $SU(5)$ GUT model, the masses of the leptons and the corresponding down-type quarks must be equal. i.e. $m_e=m_d$, $m_\mu=m_s$, $m_\tau=m_b$. Whereas this is approximately correct for ...
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206 views

Hypercharge normalization for $SU(5)$ GUT

Reading about $SU(5)$ unification, texts says that they use the renormalization factor $\sqrt{3/5}$ for weak hypercharges in order to embed SM into a $SU(5)$ group. This implies a new $U(1)_Y$ ...
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Why does the conclusion that protons are monopoles has led us to believe that they specifically may have a half-life? [closed]

from Zeldovich, Ya. B.; Khlopov, M. Yu. (1978). "On the concentration of relic monopoles in the universe": "The majority of particles appearing in any quantum field theory are unstable, and they ...
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$SU(5)$ group theory: Contracting three adjoints to make a singlet

There's probably a trivial answer to my question, but I'm having trouble finding it. In an $SU(5)$ GUT, we have a gauge field, $A_{\mu} = A^{a}_{\mu}T^{a}$ which lives in the $24 (\text{Adjoint})$ ...
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Sun's energy and grand unification

According to Wikipedia, The approximate grand unification energy value is equal to $1×10^{25}$ eV or $10^{16}$ GeV This is equal to $1602176$ J. Now, The Earth receives 174 petawatts (PW) ...
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These terms are so foreign to me that they feel like unnecessary jargon; what do these terms mean, and are they relatively common?

No pun intended in the title. ;) I am having trouble understanding this sentence on Wikipedia's page for Unified Field Theory: Governed by a global event $\lambda$ under the universal topology, ...
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Decomposition of the complex conjugate of the fundamental representation of $SU(5)$ in $SU(3)\times SU(2)\times U(1)$

I know I can decompose the fundamental representation (denoted as $5$) of $SU(5)$ as: $$ (3,1)_{-2c/3} \oplus (1,2)_{c} $$ But how do I get the decomposition of the complex conjugate of this ...
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Runaway Monopole Catalyzed Baryon Decay

I am a layman in the subject, but I have recently learned that magnetic monopoles could be used to induce baryon decay (Callan-Rubakov mechanism), according to some GUTs. I have also learned that ...
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109 views

Can $E_8 \times E_8$ contain the standard model?

I know $E_8$ by itself can't be gauge group because it has no complex representation and so would not be chiral. But assuming the existence of mirror matter which also would have $E_8$ gauge group ...
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Why should proton decay into positron rather than antimuon?

Grand unification theories, such as $SU(5)$/$SO(10)$/SUSY variants, suggest proton decay. The lack of observational evidence for proton decay rules out simple GUTs. But wait a minute! The GUT's ...
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43 views

Running of gravitational constant versus. other coupling constants, GUT and TOE

Is there any theory that proves convincingly that the gravitational constant runs with energy AND it is like the other coupling constants and converge at a single point at a given energy? Or is that a ...
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Unification of the strong and electromagnetic interaction

Is it somehow possible to theoretically unify the electric charge in electromagnetic interaction with the colour charge in the strong interaction and how these charges give rise to the respective ...
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What is the status of SUSY GUTs in 2018?

Grand unification theories (GUTs) generically predict proton decay, and many of them have been under pressure for decades as experiments have failed to see it. I don't think there have been recent ...
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$SU(5)$ representation and higher anti-symmetric traces

In Zee QFT book v2 p.411 eq.16-17, he shows the SU(5) gauge theory anomaly cancellation by the following: The 1st line in fundamental of SU(5) $$ tr(T^3)=3(+2)^3+2(-3)^3=30, $$ is easy to follow, ...
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Symmetry breaking of $SO(10)$ or $Spin(10)$

The Spin(10) grand unification has a symmetry breaking of SO(10), or Spin(10). In Wikipedia, it says, "The symmetry breaking of SO(10) is usually done with a combination of (( a $45_H$ OR a $54_H$...
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Does the sedenion algebra offer a grand unification theory?

Stephane Bronoff in The Standard Model of Particle Physics from Sedenions claims that studying the left-multiplication map of unit doubly-pure sedenions solves several mysteries of the standard model. ...
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Thought Experiments to Corroborate Unification

Apart from beauty, is there reason to believe the known forces to be parts of one "superforce?" The response to a similar question seems incomplete in that it does not address unification; there is ...
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What dictates the Higgs potential of the Standard model?

As far as I know, there is no convincing answer for why does the Higgs potential has a 'Mexican hat' shape. Apart from Lorentz invariance and gauge invariance, the Higgs potential of the Standard ...
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$\mathbb{Z}_6$ symmetry in the Standard Model

It's a well-known result that the spontaneous symmetry breaking of $SU(5)$ would lead not to the usual $G_{SM}=SU(3)\times SU(2)\times U(1)$, but to $G_{SM}/\mathbb{Z}_6$. However, it's also often ...
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How to decompose E6?

Hi I'm trying to understand decomposition of $E_6\to SO(10)\otimes U(1)_\psi\to SU(5)\otimes U(1)_\psi\otimes U(1)_\chi\to SU(3)_C\otimes SU(2)_L\otimes U(1)_Y\otimes U(1)^\prime$. I believe I mostly ...
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Which are the obstructions for $E_8^L\times E_8^R$ unification?

After left-right symmetry extension of the standard model, $$G' \times SU(2)^L \times SU(2)^R$$ it would seem that a logical pathway to grand unification is to try to obtain it by breaking down from ...
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Splitting the Fundamental Forces

So one interesting idea in physics is that at higher energy levels, fundamental forces fuse together (ex: Electricity and Magnetism into Electromagnetism) and (Eletromagnetism + Weak Force -> ...
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Why does the $\mu^{+}\pi^{0}$ mode in flipped SU(5) becomes more important when compared to simple SU(5)?

I know that the higgs sector of these theories are different and all that. But what is the simple reason of why $p\rightarrow\mu^{+}\pi^{0}$ becomes comparable to $e^{+}\pi^{0}$? One thing I can image ...
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Since gluon fields do not appear apart from quarks, did gluon fields first appear during the quark epoch?

Big Bang cosmology and grand unification theories say that the strong force and the electroweak force separated during the electroweak epoch, i.e., $10^{-36}$ to $10^{-32}$ seconds after the Planck ...
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Why in $SU(5)$ we do not consider $\bar{\nu}_L$?

In GUT, why in representation $\bar{5}+10$ of $SU(5)$ we do not consider $\bar{\nu}_L$? One says that there are 15 particles-antiparticles per generation but, for me, there are 16 particles-...
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Proton's half life (Energy-dependent)

Proton's half life has a lower estimated bound in 10^33 years aprox. This is due to the enormous mass of the X boson, predicted by some GUTs. So my question is: if the free proton is in a high energy ...
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Discovery of anti-deuteron and the implication of CPT violation

From this review by Antonino Zichichi 2009 and this review from T. D. Lee in 2007, it is said that Dirac is very upset when hearing the discovery of anti-deuteron (anti-matter of deuteron, the nucleus ...
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How to decompose the representation of $\rm SU(5)$?

This question comes from Srednicki's textbook "Quantum Field Theory". On pages 514-515, it states: Under the unbroken $\rm SU(3)\times SU(2) \times U(1)$ subgroup, the $5$ representation of $\rm ...
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472 views

Why are both C and CP violation necessary for baryogenesis?

Sakharov condition states both C and CP violation is necessary for baryogenesis. Now consider, for example, a theory with B-number violating interaction and C-violation. Therefore, if $p\to e^+\gamma$ ...
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Doublet-triplet splitting : Meaning of some mechanism names

In order to solve the Doublet–triplet splitting problem, people have developped several mechanisms, such as the Missing Partner, the Missing VEV and the Sliding Singlet mechanism. I couldn't really ...
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657 views

Why magnetic monopole has't been shown in the particle physics's Standard Model context?

For various reasons, experts, since Dirac, believe that a unified field theory must have a magnetic monopole. For example, Polyakov said: "I am quite certain that magnetic monopoles really exist. How, ...
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Possible intermediate scales of baryogenesis?

The conventional beyond Standard Model explanation of baryogenesis is that, within Grand Unified Theories (GUT), there exist some new heavy scalar bosons of mass $M_{\rm GUT}\sim10^{15}$ GeV, which ...
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187 views

How far are we from reaching around $10^{16}~\rm GeV$ collisions experimentally?

I understand this is a highly speculative question, so I'm not expecting final words, but rather insights to deepen my notion on the issue. I know we reached about 209GeV at LEP in the end of 2000, ...
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120 views

SUSY $SU(5)$ GUT chiral adjoint repersentations

when you have a chiral superfield in the adjoint representation in your theory (i.e the Higgs $\Sigma_{24}$ in $SU(5)$), you can write it as a $5\times5$ Matrix: $(\Sigma_{24})_i^j=\Sigma^a (t^a)_i^j$ ...