Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,047 questions , 2,200 unanswered
5,345 answers , 22,709 comments
1,470 users with positive rep
816 active unimported users
More ...

  Why did Standard Model never sense a requirement to include gravitational quantum?

+ 0 like - 6 dislike
2262 views

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)?

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Sachin Shekhar
asked Jul 6, 2012 in Theoretical Physics by Sachin Shekhar (-30 points) [ no revision ]
Most voted comments show all comments
@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.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Sachin Shekhar
@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.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Sachin Shekhar
-1. It is not that easy to simply plonk in gravity into the standard model.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Dimensio1n0
@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.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Dimensio1n0
Duplicate: physics.stackexchange.com/questions/7526/…

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Dimensio1n0
Most recent comments show all comments
Not sure what you mean ... ? It other things are included then it is no longer just THE standard model.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Dilaton
@Dilaton Then, you can safely ignore that sentence. It'd not affect the question.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user Sachin Shekhar

2 Answers

+ 5 like - 0 dislike

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.

This post imported from StackExchange Physics at 2014-03-24 03:34 (UCT), posted by SE-user anna v
answered Jul 6, 2012 by anna v (2,005 points) [ no revision ]
+ 2 like - 0 dislike

In Quantum Electrodynamics, things are simple, because the photons are uncharged, so they themselves do not interact through Electromagnetdism, . Of course, there are still divergencies, and you still do need to renormalise, but things are very simple, compared to...

Quantum Chromodynamics,. Things now get much more complicated. Well, the Lagrangian Density takes almost the same form as in Quantum Electrodynamics, but compute anything, is a horror. Why? Gluons themselves have colour charge. SSo the additional gluon potentials, which ignoring constants, is $A^\mu=\nabla^\mu-\partial^\mu$ in the contra - variant form, have colour charges themselves, and interact through the strong force themselves. And thus, there is a lot of problems with the divergencies, but still, it is renormalisable.

Since everything was renormalisable, strong coupling, weak coupling, and they could make a TOEEG (theory of everything except gravity), called the standard model, they thought the same elegance could be extended to gravity, to general relativity. I mean, the standard model does incorporate special relativity, so why not general?

The most obvious way to do so, was to introduce a gravitational quantum, the graviton. But sadly, it was done in a very naive way. The gravitons themselves contributed to the gravitational field, just like in Quantum Chromodynamics, and whatever it is, the end result diverged. But unlike in Quantum Chromodynamics, for Quantum Gravity, it was non-renormalisable,.

So, a less naive theory of gravitons is required, and such a theory is string theory.

So, thus, it was not about the standard model not sensing a requirement to include gravity, it couldn't. One needs string theory for that; to make everything known to man, and everything that is true, to come out naturally.

There are, of course, other TOQGs (theories of quantum gravity), but the problem is that most of them are lorentz asymmetric (cf. Lubos Motl's criticism to Loop Quantum Gravity), they don't allow for other forces (interactions) other than gravity, they are mathematically inconsistent, etc. Or they just lead to string theory (e.g. supergravity, kaluza - klein theory).

answered Jul 7, 2013 by dimension10 (1,985 points) [ revision history ]

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysicsOverflo$\varnothing$
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...