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.

Filter by
Sorted by
Tagged with
2
votes
1answer
84 views

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In the context of grand unification theories A.Zee's book states that $SU(5)$ (or $SO(10)$ if $SU(5)$ is considered as outdated as GUT candidate) as GUT and as spontaneously broken non-abelian gauge ...
2
votes
1answer
126 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 ...
2
votes
1answer
308 views

How to break a irreducible representation into its subgroups

In Grand Unified Theories (though I'm sure this a general group theory result) people write the irreducible representations of a group (i.e., the gauge bosons) using a sum of irreducible ...
2
votes
1answer
996 views

What led to the electroweak and strong forces splitting?

Is the reason for the split believed to be spontaneous symmetry breaking? If so, did SSB occur because the Universe was cooling rapidly from extremely high temperatures?
2
votes
1answer
100 views

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 ...
2
votes
2answers
1k views

Is there any relation between weak and strong forces, similar to electric and magnetic forces?

Is it possible to unify the strong, weak, electric and magnetic field just by Maxwellian-type equations? (Maxwell by adding a small change - unified electric and magnetic field, then Einstein's ...
2
votes
0answers
22 views

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(...
2
votes
0answers
35 views

$ (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 $(1,2,-1/2)$: $$ \begin{pmatrix} \nu\\e \end{pmatrix} $$ ...
2
votes
0answers
27 views

$SU(5)$ 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 ...
2
votes
0answers
66 views

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 $$ (\...
2
votes
0answers
38 views

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 ...
2
votes
1answer
48 views

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 ...
2
votes
0answers
93 views

Invariant linearly independent scalar potential construction for product groups

Lets say one has a gauge group for example SU(n) or SO(n) and has a scalar field which belongs to a certain representation (m-ranked tensor). If one wants to write down the invariant potential for the ...
2
votes
0answers
391 views

What insights does category theory offer in terms of grand unified theories?

What insights does category theory offer in terms of grand unified theories? Any references to books or papers that give categorical descriptions of any of the common grand unified theories would be ...
2
votes
0answers
72 views

How well theoretically motivated is $R$-parity?

I understand that $R$-parity is empirically necessary in order to avoid proton decay, but theoretically I'm worried that it amounts to a tune or "hack" that spoils the naturalness argument for ...
2
votes
1answer
108 views

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 ...
1
vote
1answer
258 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 ...
1
vote
2answers
528 views

Simple PDE as a theory of everything?

For the sake of simplicity, I’d like to believe that there is one master non-linear partial differential equation governing physics. In particular, consider a Klein-Gordon form: $$ \frac{\partial^2 ...
1
vote
1answer
113 views

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 ...
1
vote
1answer
188 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, ...
1
vote
3answers
459 views

Will the Graviton discovery mean the end of the General Relativity [closed]

I know that this question has been addressed in one form or the other however I would appreciate some other thoughts - other then "GR works so it doesn't matter what's behind it". In fact it does ...
1
vote
1answer
282 views

What are the problems that physicists face while searching for the grand unified theory (GUT)? [closed]

I would like to know the missing links in the grand unification and what are the possible candidates for those missing links.
1
vote
1answer
62 views

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). ...
1
vote
1answer
101 views

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 -> ...
1
vote
1answer
60 views

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.
1
vote
2answers
271 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 $U(1)_Y$ ...
1
vote
1answer
52 views

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 ...
1
vote
1answer
64 views

Why does non-abelianity implies a single coupling constant?

Why does a theory described by a non-abelian group has only a single coupling constant $g$? While on the other hand in an abelian theory, as Electromagnetism, each charged particle has its own charge ...
1
vote
1answer
500 views

Plot of gauge coupling unification [closed]

(Zoom in here to see the scales.) About the result of plotting running of 3 coupling constant, we think that we should get the correct one(MSSM). But we get discontinuity at $ M_{susy}$. If there ...
1
vote
0answers
68 views

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 ...
1
vote
0answers
45 views

$\rm SO(10)$ 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 ...
1
vote
0answers
59 views

How to give left-handed neutrinos alone Majorana mass?

On Wikipedia, it says https://en.wikipedia.org/wiki/Georgi–Glashow_model#Breaking_SU(5): Fermions transforming as a 1 under SU(5) are now thought to be necessary because of the evidence for neutrino ...
1
vote
0answers
24 views

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 $[3]_4$ ...
1
vote
0answers
69 views

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 ...
1
vote
0answers
26 views

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), ...
1
vote
2answers
101 views

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 ...
1
vote
0answers
15 views

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 ...
1
vote
0answers
27 views

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 ...
1
vote
0answers
76 views

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 ...
1
vote
0answers
47 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 ...
1
vote
0answers
69 views

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 ...
1
vote
0answers
94 views

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 ...
1
vote
0answers
24 views

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 ...
1
vote
0answers
45 views

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 ...
1
vote
1answer
138 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: $(\Sigma_{24})_i^j=\Sigma^a (t^a)_i^j$ ...
1
vote
0answers
37 views

Trinification lepton Yukawa interactions

We have a trinification model of $SU(3)_c\otimes SU(3)_L\otimes SU(3)_R$, where the first is the usual colour group, the second a left $SU(3)$ and the third a right $SU(3)$. As usual, leptons and ...
1
vote
0answers
143 views

What sorts of problems does asymptotically safe gravity face as a potential quantum gravity solution?

I've recently read an article by Ethan Siegel over at Forbes (he also blogs at Starts with a Bang) on asymptotically safe gravity as a possible alternative to string theory. I read the author's blog ...
1
vote
0answers
43 views

Why do the gauge bosons fix the couplings of the SM?

In chapter Chapter 16: Grand Unified Theories in the very first paragraph, the author states Note the SM gauge interactions of quarks and leptons are completely fixed by their gauge charges. Why is ...
0
votes
2answers
100 views

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, ...
0
votes
1answer
92 views

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 ...