Could chirality in LQG break the electroweak symmetry without the higgs?

1. Sep 22, 2007

ensabah6

One difference between GR and LQG is that LQG is chiral, whereas GR is not. In order to break the electroweak symmetry, a higgs field needs to be introduced by hand.

Einstein's understanding of inertia implies a strong EP as gravitational mass and inertia are identical,

while a higgs field allows for a weak EP as inertia is given by the higgs field

I wonder whether LQG's chirality could play the role of the higgs in breaking the electroweak symmetry. One obvious prediction is that the LHC will not see neither a higgs nor technicolor nor top quark condensates.

Last edited: Sep 23, 2007
2. Sep 23, 2007

Haelfix

"hence Einstein's strong EP implies that inertia is given by the higgs field, allowing for a weak EP."

This is approximately 90% false. Most inertia comes from quark-gluon interactions.

As for the absense of any Higgs or higgs like particle, this is immediately ruled out by partial wave unitarity bounds.

3. Sep 23, 2007

ensabah6

I rephrased,

Interesting, does partial wave unitarity bounds rule out top quark condensation and technicolor models as well?

I had thought GR'ers thought higgs inelegant as inertial mass is given by the gravitational field and geometry rather than a higgs field.

4. Sep 23, 2007

BenTheMan

ensabah---

I am interested to see where this discussion goes. As you probably know, there are lots of people working on new higgsless theories, people like Tony Gherghetta (I think), Caba Csaki, along with people whose names I forget at Michigan State (I know some of the grad students).

The interesting thing is that these new higgsless models turn out to be the AdS/CFT duals of things like technicolor and such.

Anyway, maybe I am being foolish here, but how could one implement your idea?

5. Sep 23, 2007

josh1

LQG is a purely gravitational theory, so how would it even know where the electroweak scale is?

6. Sep 23, 2007

marcus

Ensabah, was your post referring in part to the talk Smolin is giving this week in Brazil?
"Emergence of chiral matter from quantum gravity"
==quote from abstract==
Loop quantum gravity is an approach to quantum gravity which follows from a non-perturbative, background independent quantization of diffeomorphism invariant gauge theories, including general relativity. The dynamics is best understood in terms of thbe path integral formulation, known also as spin foam models.

In the last two years it has been understood that these models have in some cases emergent chiral excitations, which can be interpreted as chiral matter degrees of freedom. As shown by Markopoulou et al these can be understood as noiseless subsystems in the language of quantum information theory. This provides a tool to study the excitations and spectra of models of dynamical quantum geometry. In the simplest such model studied, due to Bilson-Thompson, Markopoulou and Smolin, the simplest of these excitations correspond to the fermions of the standard model. The correspondence arises through a topological preon model introduced by Bilson-Thompson.

I will review the basics of loop quantum gravity and spin foam models necessary to understand these results. I will close with new results with Yidun Wan on the propagation and interactions of chiral excitations in models of quantum gravity.
==endquote==

http://www.sbf1.sbfisica.org.br/eventos/enfpc/xxviii/sys/resumos/R0326-1.pdf
Several other related papers and recent talks were mentioned. If that is part of what you have in mind, I will get the links. If not, please explain your idea more.

Last edited: Sep 23, 2007
7. Sep 23, 2007

ensabah6

josh1 BenTheMan marcus,

While I am not ruling out what you say what I have in mind is this article:

Title: Isogravity: Toward an Electroweak and Gravitational Unification
Authors: Stephon H. S. Alexander
Categories: physics.hep-th High Energy Physics - Theory

arXiv:0706.4481

"Abstract: We present a model that unites the electroweak interaction with general relativity without specifying a space-time metric. This is made possible by embedding the kinetic terms for gravity and electroweak theory using one $\SL$ connection variable. The gauge theory is specified without relying on a space-time metric. We show that once a symmetry breaking mechanism is implemented that selects a global time-like direction, the electroweak theory and general relativity emerges with their associated massless degrees of freedom; the spin 1 vector boson and the spin 2 graviton."

8. Sep 23, 2007

ensabah6

LQG as such may be, but Stephon H. S. Alexander "Isogravity: Toward an Electroweak and Gravitational Unification" shows how one can do this in Ashketar variables.

9. Sep 23, 2007

ensabah6

NOt really my idea Stephon H. S. Alexander here writes of "Isogravity: Toward an Electroweak and Gravitational Unification" "We show that once a symmetry breaking mechanism is implemented that selects a global time-like direction, the electroweak theory and general relativity emerges with their associated massless degrees of freedom; the spin 1 vector boson"

I want to stress that his theory allows for adding the higgs field by hand. What I wonder is this: if LHC or tev do not find the higgs, and no other evidence comes in for the higgs, and no other explanation such as technicolor and top quark condensate models are forthcoming, could Isogravity offer a higgless ground state that breaks electroweak symmetry?

Last edited: Sep 23, 2007
10. Sep 23, 2007

josh1

There was no indication in your question that you we're considering a theory which goes beyond lqg by including electroweak physics. Maybe it should've been obvious to me that you we're. If so, sorry for my blockheadedness.

11. Sep 23, 2007

Haelfix

"Interesting, does partial wave unitarity bounds rule out top quark condensation and technicolor models as well?"

Unitarity bounds aren't strong enough to rule them out. However theories like that coupled with a few extra considerations, will heavily constrain what the result can be.

I mean it affects the "space" that technicolor theories can live in (shrinking it). The early (and simplest) versions of technicolor have been heavily disfavored for quite some time now.

You can still make it work (and there is a nonzero chance of actually seeing it), but its no longer the minimal and natural (not much finetuning) model that it once was.

12. Sep 24, 2007

ensabah6

A well known implication of LQG is chiral self-dual variables, and I wonder whether this in itself could break EW if LHC does not find a higgs.

13. Sep 24, 2007

ensabah6

Marcus,
in principle preon theory states all particles are composite, so a composite theory of the SM would not need a higgs to break EW symmetry, but of course, preon models and composite models themselves are not mainstream by a long shot, but then again, LQG is not mainstream either.

14. Sep 24, 2007

josh1

Are you or are you not talking about lqg as a purely gravitational theory?

15. Sep 25, 2007

marcus

Refresh my memory, clearly the original 2005 Bilson-Thompson paper was about a preon model but a lot has changed since then.
Where do you see preons in the current (2007) work?
There's Smolin's ILQGS talk, and his Loops 07 talk, and Yidun Wan's Perimeter talk all three from this year. But aside from the obvious HISTORICAL reference, I don't recall any mention of preons. Point me to a particular slide.

As I see it, a bold risky attempt to get ordinary particles (not preons, but quarks and electrons etc) from tangles in a spin network. These tangles are able to propagate and interact with other tangles---but in none of the diagrams I have seen in the various talks are the tangles "composite" in any obvious sense. Check out the sources---maybe you will find something I missed.

Last edited: Sep 25, 2007
16. Sep 25, 2007

ensabah6

Could LQG as a purely gravitational theory (theory of spacetime) break EW symmetry, or LQG in various extensions (i.e Smolin's braiding, Alexander's isogravity)

17. Sep 25, 2007

ensabah6

Hi Marcus,

Now that you brought it to my attention, a lot has changed since then. I do not see preons in the current work. It's not clear to me whether his model makes use of a higgs. So has there been a posting on his trip in Brazil updating the current progress?

18. Sep 26, 2007

marcus

I don't know of any posting about the Brazil trip. The most recent thing I know is Yidun Wan's talk
http://pirsa.org/07090011/
Propagation and interaction of topological invariants on embedded 4-valient spinets ( Windows Media , MP3 Audio , PDF)
Yidun Wan - University of Waterloo
Abstract: The study of particle-like excitations of quantum gravitational fields in loop quantum gravity is extended to the case of four valent graphs and the corresponding natural evolution moves based on the dual Pachner moves. This makes the results applicable to spin foam models. We find that some braids propagate on the networks and they can interact with each other, by joining and splitting. The chirality of the braid states determines the motion and the interactions, in that left handed states only propagate to the left, and vice versa.
Date: 07/09/2007

Last edited: Sep 26, 2007
19. Sep 27, 2007

ensabah6

I wasn't thinking of this specifically, I was wondering whether the vacuum state of LQG, given Randanomo's interpretation of the Ashketar variables and immirizi parameter implies that the chirality and parity violation of the LQG vaccuum would by itself be enough to breatk EW symmetry without a Higgs, in the event TEVATRON or LHC does not find a higgs, whether the chiral aspect of the Ashketar variables and Immirizi parameter can break SU(2)XU(1)

20. Oct 2, 2007

BenTheMan

Well, suppose that LQG CAN break the electroweak symmetry by giving the vacuum quantum numbers. Then it seems to me that all of the symmetries should break at the planck scale, or LQG must give some mechanism that this isn't true... This would mean that LQG would have a moduli stabilization problem of its own.

marcus---

Instead of blindly linking to abstracts, do you think you might sumarize some of this work for us?