Relationship between electron and quark charge

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Discussion Overview

The discussion explores the relationship between the charge of electrons and quarks, questioning whether there is a fundamental connection between these particles, potentially through frameworks like string theory or grand unified theories (GUTs). The conversation touches on theoretical implications, symmetry breaking, and the nature of charge in particle physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that the simple charge ratio of 1/3:1 between quarks and electrons suggests a deeper connection, possibly in string theory.
  • Others discuss the requirement for the total charge in each generation of fermions to sum to zero, noting that quarks contribute differently due to their color charge.
  • A participant expresses confusion about why protons and electrons have opposite charges despite being fundamentally different, suggesting a potential underlying relationship.
  • Grand unified theories are mentioned as frameworks that might explain the relationship between quarks and leptons, positing that they are the same at high energies but differentiate at lower energies due to symmetry breaking.
  • Some participants note that while GUTs relate particle charges, they have not been successful in describing observed phenomena, particularly regarding proton decay.
  • There is a suggestion that charge may be more fundamental than the particles themselves, with electrons representing a specific combination of electric and baryonic charge, while quarks represent a different combination.
  • Further inquiry is made into how quarks and leptons relate if charge is indeed more fundamental, with references to symmetry breaking as a potential explanation.

Areas of Agreement / Disagreement

Participants express a range of views on the relationship between quarks and leptons, with some supporting the idea of a fundamental connection and others questioning the implications of current theories. No consensus is reached on the nature of this relationship.

Contextual Notes

The discussion includes unresolved questions about the nature of charge, the implications of grand unified theories, and the experimental validation of these theories. Participants acknowledge the complexity of the topic without arriving at definitive conclusions.

a dull boy
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Dear Physics Forum,

Is there any model where the electron and quark share a fundamental relationship, maybe in some string theory? I ask because it seems too much of a coincidence that two completely
independent particles would have a simple charge relationship of 1/3:1 .

Thanks, Mark
 
Physics news on Phys.org
Cancellation of anomalies requires that the total charge in each generation of fermions must add up to zero. (Since they come in three colors, quarks must be counted with a weight of three.) Thus, up + down + electron + neutrino = 3(2/3) + 3(-1/3) + (-1) + 0 ≡ 0.
 
Bill_K said:
Cancellation of anomalies requires that the total charge in each generation of fermions must add up to zero. (Since they come in three colors, quarks must be counted with a weight of three.) Thus, up + down + electron + neutrino = 3(2/3) + 3(-1/3) + (-1) + 0 ≡ 0.

Thanks for your response. I think I understand your statement - that theory requires the total charge in each generation to = zero, but I still don't understand why in fact (in an experimental sense) this is so. Why do the proton and electron have identical but opposite charges despite being made of very different things? It seems to coincidental to be a coincidence - meaning maybe they are related to each other in some more fundamental way.
 
Grand unified theories can offer an explanation of this, by positing that quarks and leptons are the same at high energies but become different due to symmetry breaking at low energies. But relationships between these particles survive at low energies including simple ratios between their charges.
 
Sure enough, many GUTs do contain constraints that relate the charge of different particles. And for a time, people thought that pursuing GUTs would turn out to be fruitful. Unfortunately they also contain a prediction about the rate at which protons decay, which experiment has failed to detect. While GUTs are an appealing idea, they fail to describe the world we live in, and are not at present a serious alternative to the Standard Model.
 
a dull boy said:
Dear Physics Forum,

Is there any model where the electron and quark share a fundamental relationship, maybe in some string theory? I ask because it seems too much of a coincidence that two completely
independent particles would have a simple charge relationship of 1/3:1 .

Thanks, Mark

Maybe you look at it the wrong way round. Charges are more fundamental than elementary particles. So there are different combinations of charges. An electron is some value of electric charge in combination with zero of baryonic charge, while a quark is a non-zero combination of both charges.
 
DrDu said:
Maybe you look at it the wrong way round. Charges are more fundamental than elementary particles. So there are different combinations of charges. An electron is some value of electric charge in combination with zero of baryonic charge, while a quark is a non-zero combination of both charges.

That is intriguing. I'd like to push on it a little. I agree that charge must be more fundamental than either quarks or leptons, I think that is what I'm trying to understand - if charge is more fundamental, then how are quarks related to leptons? The idea that BillK and The Duck referred to - that there are no leptons or baryons at high energies, and these particles result from symmetry breaking at low temperatures seems a satisyfing explanation.

There must be some issue at hand regarding charge being a component of both leptons and quarks, given the attempts to explain this through grand unified theories.
 
a dull boy said:
That is intriguing. I'd like to push on it a little. I agree that charge must be more fundamental than either quarks or leptons, I think that is what I'm trying to understand - if charge is more fundamental, then how are quarks related to leptons? The idea that BillK and The Duck referred to - that there are no leptons or baryons at high energies, and these particles result from symmetry breaking at low temperatures seems a satisyfing explanation.

There must be some issue at hand regarding charge being a component of both leptons and quarks, given the attempts to explain this through grand unified theories.

Indeed , I would like to know that as well. A more in depth answer over why two fundamentally different particles share similar property of having a 'charge density' .
 

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