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

New features!

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

123 submissions , 104 unreviewed
3,547 questions , 1,198 unanswered
4,551 answers , 19,358 comments
1,470 users with positive rep
411 active unimported users
More ...

What do "tachionic" neutrinos mean for QG?

+ 4 like - 0 dislike
27 views

Reading about the spectacular Opera claim, I`m (again ;-P) wondering if a confirmation of superliminous neutrinos could help settle some still open quantum gravity issues ...?

In this post, Lumo explains why tachyons should better be bosonic if they exist, making use, among other things, of some string theoretical considerations.

So what would a confirmation of the claim mean for string theory?

On the other hand, would a confirmation of superluminal neutrinos and a corresponding incompleteness of GR (and allowance to violate Lorenz Invariance?) lend some "updraft" to other QG theories like LQG, spin foams, spin networks etc or even provide some positive hint of them?

asked Sep 23, 2011 in Phenomenology by Dilaton (4,175 points) [ revision history ]
recategorized Mar 17, 2014 by dimension10
Take it to chat, please. The site is not well served by numerous subtly distinguished duplicates when the odds are this all blows over in a few months.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user dmckee
@dmckee What I wanted to know is NOT addressed neither in any of the others similar questions nor in the corresponding answers and discussions. So can I edit and try again or is it completely pointless?

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user Dilaton
I've asked the other mod to review my actions. My position would be that every modern theory needs tearing up and rebuilding from the ground, so the impact is the same on them all, but perhaps the theorists feel differently.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user dmckee
@dmckee Ok thanks, I`m very interested in what different theorists have to say (this was the goal of my question). And I exchanged a tag; I mixed up general physics and general relativity. What I wanted to attach was general relativity of course ...

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user Dilaton
I think it's fine to have a question that focuses on quantum gravity specifically, especially now that the news is no longer immediately current. There's a lot of physics that has been more-or-less directly confirmed by measurement, so even if relativity breaks, we wouldn't necessarily have to start from scratch with everything.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user David Z
@DavidZaslavsky ...so will my question be reopened?

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user Dilaton
...sure, why not, seeing as how nobody else has chimed in.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user David Z

1 Answer

+ 4 like - 0 dislike

For this post I will assume that the observation of neutrinos faster than light is accurate and not further mention this assumption below.

Of the particles whose speeds have been accurately measured, the neutrino is unique in that it does not participate in electromagnetic interactions. The graviton also does not participate in electromagnetic interactions and so we might expect its velocity to also exceed that of light. This has immediate impact on quantum gravity and would open up a wide range of new theories.

Since neutrinos can be used to send a signal, their moving faster than light destroys the relationship between causality and arbitrary reference frames which forms an important part of the special theory of relativity. To get causality to function again, we have to choose one reference frame as the preferred one and then let that reference frame define causality for all others. This variation of the special theory of relativity is sometimes called "Lorentzian Relativity" or "neo-Lorentzian Relativity" or "Lorentz Ether Theory", and has been explored by fringe physicists for most of the last 100 years.

The presence of a preferred reference frame in the special theory of relativity implies that one must also be present in general relativity. This makes theories that assume a "background metric" more interesting. Of such theories, my favorite is the one found by the Cambridge Geometric Algebra Research Group. For example, see Gravity, Gauge Theories and Geometric Algebra, Anthony Lasenby, Chris Doran, Stephen Gull, Phil. Trans. R. Soc. Lond. A 356, 487-582 (1998). This theory gives the observable predictions of GR exactly, but avoids wormholes and other topological things as it is built on a flat background metric. Rather than tensors, it uses the gamma matrices used in the rest of particle physics.

In terms of the damage to relativity as compared to the damage to quantum mechanics, an accepted observation of superluminal neutrinos would be more damaging to relativity. So I would think that the general effect on quantum gravity would be to make it more quantum and less (traditional) gravity.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user Carl Brannen
answered Sep 27, 2011 by Carl Brannen (240 points) [ no revision ]
Thanks, this looks interesting +1, I will look at these papers.

This post imported from StackExchange Physics at 2014-03-17 03:43 (UCT), posted by SE-user Dilaton

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$\hbar$ysicsOverf$\varnothing$ow
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).
To avoid this verification in future, please log in or register.




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

Your rights
...