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Standard Model is advanced (lorentz invariant) version of Quantum physics. It tried to include everything which came in the way while understanding quantum world. It even didn't bother to include even Higgs Boson which was hypothetical at that time. Did they never find gravitation in the way of other quantum interaction.

Note: I know, there were many unsuccessful attempts to add gravitation with SM to make Theory of Everything. My question: Why didn't Standard Model keep gravitation as raw ingredients (with unresolved relationship with others)?

Abhimanyu Pallavi Sudhir
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Earth is a Spoon
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    Firstly, the concept of the Higgs actually came into play when the SM was being integrated--it fixed a problem with the electroweak interaction. Secondly, the SM wasn't "planned"--it sprouted bit by bit from the unification of forces. Thirdly, it's not as simple to "add" gravitation as a raw ingredient--there's a lot of mathematics behind it, and anyway, like I said, the model was built when the theory behind each force was being unified. – Manishearth Jul 06 '12 at 06:17
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    Also, keeping gravity with an unresolved relationship with others makes no sense--these models attempt to explain the working of the forces mathematically. "Keeping gravity with an unresolved relationship" is exactly the same as "assuming that some day, gravity will be added". I see no difference, can you clarify on that? – Manishearth Jul 06 '12 at 06:19
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    I disagree with the first sentence of the last paragraph. It is too early to decide if the attempts for a TOE are successful or not; and they are still work in progress ... – Dilaton Jul 06 '12 at 18:27
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    The standard model is just defined as the low energy theory excluding gravity. It isn't that people willfully excluded gravity, that's just not what the theory is describing. It is therefore incomplete in this way, but it is complete in every other way (so far). The low energy theory is an important thing to understand, so people weren't wasting time making the standard model. Also, the Higgs was a part since the beginning in 1967. What's the question exactly? – Ron Maimon Jul 06 '12 at 18:35
  • @Ron Can you settle down with your standard model equations if gravitational field interfered as a Ghost? That's the question... – Earth is a Spoon Jul 06 '12 at 19:05
  • @Manishearth You can't write down even a single field equation in Standard Model if a ghost quantum is interfering with it. My question is floating around it.. – Earth is a Spoon Jul 06 '12 at 19:09
  • @Dilaton I think, Standard Model is flexible even today to include something.. – Earth is a Spoon Jul 06 '12 at 19:12
  • Not sure what you mean ... ? It other things are included then it is no longer just THE standard model. – Dilaton Jul 06 '12 at 19:22
  • @Dilaton Then, you can safely ignore that sentence. It'd not affect the question. – Earth is a Spoon Jul 06 '12 at 20:02
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    @SachinShekhar: Huh? What does that mean? The gravitational field is not a ghost. It has positive propagators in the physical part. This is also a completely different question. I am voting to close. – Ron Maimon Jul 07 '12 at 05:03
  • @Ron That's my question.. gravity is real as you've said. But, from the perspective of SM, it'd be ghost if it'd have interfered. – Earth is a Spoon Jul 07 '12 at 06:31
  • @Ron See the answer. It says that SM excluded gravity because it didn't have any effect on equations of SM. So, it couldn't see any ghost force. – Earth is a Spoon Jul 07 '12 at 06:34
  • -1. It is not that easy to simply plonk in gravity into the standard model. – Abhimanyu Pallavi Sudhir Jul 07 '13 at 04:16
  • @SachinShekhar: It is not about ghost fields. The reason is simply that the path integral (or other peturbations) diverged and were not renormalisable so they let other people, like string theorists, do that work for them. – Abhimanyu Pallavi Sudhir Jul 07 '13 at 04:46
  • Duplicate: http://physics.stackexchange.com/questions/7526/gravity-and-the-standard-model – Abhimanyu Pallavi Sudhir Aug 11 '13 at 13:15

2 Answers2

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Read this link to get a framework of where the SM stands as far as interactions go. The SM is a mathematical shorthand of our data for the microcosm of quarks and leptons.

Look at table 1 and you will see that at the level of quarks and leptons the gravitational interaction is so weak that it is completely irrelevant and certainly its effect on the values used in the standard model cannot be measured with our present experimental accuracies.

anna v
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Gravitons interact with each other, which causes divergences in a naive quantum theory of gravity. This kind of thing happens with quantum electrodynamics too (gluons have colour charges), but the divergences can be renormalised, which can't be done with gravity.

Abhimanyu Pallavi Sudhir
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